Ndza khensa ku endzela nature.com. Vuhundzuluxi bya browser lebyi u byi tirhisaka byi na nseketelo wa CSS lowu nga nyawuriki. Leswaku u kuma ntokoto lowunene, hi ringanyeta ku tirhisa browser leyintshwa (kumbe ku tshikisa movha wa ku fambisana eka Internet Explorer). Hi nkarhi wolowo, ku tiyisisa nseketelo lowu yaka emahlweni, hi ta kombisa sayiti handle ka switayele na JavaScript.
Electrosynthesis ya adipic acid (a precursor ya nylon 66) kusuka eka CA oil (nkatsakanyo wa cyclohexanone na cyclohexanol) i maqhinga lawa yanga heriki lawa yanga siva maendlelo ya ndzhavuko lawa ya lavaka swiyimo swo tika. Hambiswiritano, low current density xikan’we naku phikizana ka oxygen evolution reactions swihunguta swinene matirhiselo ya yona ya ti indasitiri. Eka ntirho lowu, hi cinca nickel double hydroxide na vanadium ku ndlandlamuxa density ya sweswi na ku hlayisa vukorhokeri bya le henhla bya faradaic (>80%) eka nhlayo yo anama ya vuswikoti (1.5–1.9 V vs. reversible hydrogen electrode). Tidyondzo ta swikambelo na tithiyori ti paluxe mintirho yimbirhi ya nkoka ya ku cinca ka V, ku katsa na ku hatlisisiwa ka ku pfuxetiwa ka catalyst na ku antswisiwa ka cyclohexanone adsorption. Tanihi vumbhoni bya mhaka, hi ake nhlengeletano ya membrane-electrode leyi humelerisaka adipic acid leyi nga na vukorhokeri bya le henhla bya faradaic (82%) na vuhumelerisi (1536 μmol cm-2 h-1) eka density ya sweswi leyi fambelanaka na tiindasitiri (300 mA cm-2), loko hi ri karhi hi fikelela ku tshamiseka >50 h. Ntirho lowu wukombisa catalyst leyi tirhaka kahle eka electrosynthesis ya adipic acid leyingana vuhumelerisi byale henhla xikan’we na vuswikoti bya ti indasitiri.
Adipic acid (AA) i yin’wana ya ti aliphatic dicarboxylic acids ta nkoka swinene naswona yitirhisiwa ngopfu eka vuhumelerisi bya nylon 66 na ti polyamides tin’wana kumbe ti polymers1. Eka ti indasitiri, AA yi endliwa hiku oxidizing nkatsakanyo wa cyclohexanol na cyclohexanone (i.e., AA oil) hiku tirhisa 50–60 vol% nitric acid tani hi oxidizing agent. Endlelo leri ri na swivilelo swa mbango leswi fambelanaka na ku humesiwa ka nitric acid leyi hlanganisiweke na ti nitrogen oxides (N2O na NOx) tanihi tigasi ta greenhouse2,3. Hambi leswi H2O2 yinga tirhisiwaka tani hi xitirhisiwa xin’wana xa green oxidizing agent, ntsengo wa yona wale henhla xikan’we na swiyimo swo tika swa synthesis swiendla leswaku switika ku tirhisiwa hindlela leyi tirhaka, naswona ndlela leyinga durhiki swinene naku tshamiseka ya laveka4,5,6.
Eka khume ra malembe lawa yanga hundza, maendlelo ya electrocatalytic chemical na fuel synthesis ya koke nyingiso lowu andzaka kusuka eka vativi va sayense hikokwalaho ka swipfuno swa wona swaku tirhisa eneji leyi pfuxetiwaka naku tirha ehansi ka swiyimo swo olova (xikombiso, mahiselo ya kamara na ntshikelelo wa ndzhawu)7,8,9,10. Eka mhaka leyi, ku tumbuluxiwa ka electrocatalytic conversion ya KA oil kuya eka AA swina nkoka swinene kuva ku kumiwa swipfuno leswinga laha henhla xikan’we naku herisa kutirhisiwa ka nitric acid na nitrous oxide emissions leswi hlanganaka na swona eka vuhumelerisi bya ntolovelo (Figure 1a). Ntirho wa vuphayona wu endliwile hi Petrosyan na van’wana, lava vikeke electrocatalytic oxidation reaction ya cyclohexanone (COR; cyclohexanone kumbe cyclohexanol switala ku dyondzeriwa tani hi leswi yimelaka oil ya KA) eka nickel oxyhydroxide (NiOOH), kambe density yale hansi ya current (6 mA cm-2) na mbuyelo wa AA wo ringanela (52%) aswiri tano ku kumiwile11,12. Kusukela kwalano, nhluvuko lowukulu wu endliwile eka nhluvukiso wa ti catalysts leti simekiweke eka nickel ku ndlandlamuxa ntirho wa COR. Xikombiso, xihlohloteri xa nickel hydroxide (Cu-Ni(OH)2) lexi cheriweke koporo xi endliwile ku tlakusa ku hambanisiwa ka Cα–Cβ eka cyclohexanol13. Sweswinyana hi vikile Ni(OH)2 catalyst leyi cinciweke hi sodium dodecyl sulfonate (SDS) ku tumbuluxa microenvironment ya hydrophobic leyi fuwisaka cyclohexanone14.
a Mintlhontlho ya vuhumelerisi bya AA hi electrooxidation ya oyili ya KA. b Ku pimanisiwa ka electrocatalytic COR ya swihlohloteri leswi simekiweke eka Ni leswi vikiweke khale na xihlohloteri xa hina eka sisiteme ya tielektrode tinharhu na sisiteme ya betri yo khuluka11,13,14,16,26. Vuxokoxoko bya vuxokoxoko bya tipharamitha ta nhlamulo na matirhelo ya nhlamulo swi nyikiwile eka Tithebulu to Engetela ta 1 na 2. c Matirhelo ya catalytic ya swihlohloteri swa hina swa NiV-LDH-NS swa COR eka H-cell reactor na MEA, leswi tirhaka eka nxaxamelo wo anama wa vuswikoti.
Hambi leswi maendlelo lawa yanga laha henhla ya antswiseke ntirho wa COR, ti catalysts leti hlamuseriweke leti sekeriweke eka Ni ti kombisile vukorhokeri byale henhla bya AA Faraday (FE) (>80%) ntsena eka ti potentials tale hansi swinene, hi ntolovelo ehansi ka 1.6 V loko ku pimanyisiwa na reversible hydrogen electrode (RHE, leyi pfuxetiweke VRHE). Xisweswo, density ya xiphemu xa current leyi vikiweke (i.e., density hinkwayo ya current leyi andzisiweke hi FE) ya AA yi tshama yiri ehansi ka 60 mA cm−2 (Xifaniso 1b na Tafula ro Engetela 1). Nhlayo yale hansi ya current yile hansi swinene ka swilaveko swa indasitiri (>200 mA cm−2)15, leswi kavanyetaka swinene thekinoloji ya electrocatalytic eka high-throughput AA synthesis (Xifaniso 1a; ehenhla). Ku engetela density ya current, potential positive swinene (eka sisiteme ya ti electrode tinharhu) kumbe voltage yale henhla ya cell (eka sisiteme ya ti electrode timbirhi) yinga tirhisiwa, leswi kunga ndlela yo olova eka ku cinca ko tala ka electrocatalytic, ngopfu ngopfu oxygen evolution reaction (OER). Hambiswiritano, eka COR eka ti anodic potentials tale henhla, OER yinga va muphikizani lonkulu eka ku hunguta FE ya AA, hindlela yaleyo yi hunguta ku tirhisiwa kahle ka eneji (Xifaniso 1a; ehansi). Xikombiso, loko hi kambisisa nhluvuko wa khale (Xifaniso 1b na Tafula ro Engetela 1), hi vilerisiwa hi ku kuma leswaku FE ya AA eka SDS-modified Ni(OH)2 yi hungutekile ku suka eka 93% ku ya eka 76% hi ku engetela vuswikoti lebyi tirhisiweke ku suka eka 1.5 VRHE ku ya eka 1.7 VRHE14, kasi FE ya AA eka CuxNi1-x(OH)2/CF yi hungutekile ku suka eka 93% ku ya eka 69% hi ku engetela vuswikoti ku suka eka 1.52 VRHE ku ya eka 1.62 VRHE16. Xisweswo, ku vikiwa ka xiphemu xa current density ya AA ayi engeteli hiku ringana eka ti potentials tale henhla, leswi ngopfu ngopfu swi sivelaka ku antswisiwa ka matirhelo ya AA, hinga ha vuli ku tirhisiwa ka eneji yale henhla hikokwalaho ka FE yale hansi ya AA. Ku engetela eka ti catalysts leti simekiweke eka nickel, ti catalysts leti simekiweke eka cobalt titlhele ti kombisa ntirho wa catalytic eka COR17,18,19. Hambiswiritano, vukorhokeri bya tona bya hunguteka eka ti potentials tale henhla, naswona loko ku pimanyisiwa na ti catalysts leti simekiweke eka Ni, tina swipimelo swotala swa vuswikoti eka switirhisiwa swa ti indasitiri, kufana na ku cinca cinca lokukulu ka nxavo xikan’we na ti inventories letintsongo. Hikokwalaho, swa navela ku tumbuluxa ti catalysts leti simekiweke eka Ni letingana current density yale henhla na FE eka COR kuva switirha ku fikelela mbuyelo wale henhla wa AA.
Eka ntirho lowu, hi vika vanadium(V)-modified nickel layered double hydroxide nanosheets (NiV-LDH-NS) tanihi ti electrocatalysts leti tirhaka kahle ta vuhumelerisi bya AA hi ku tirhisa COR, leti tirhaka eka nxaxamelo wo anama wa vuswikoti na OER leyi tshikileriweke swinene, ku fikelela FE ya le henhla na ku tsindziyela ka sweswi eka tisele ta H na tinhlengeletano ta membrane electrode (MEAs; Xifaniso 1 b). Hi sungula hi kombisa leswaku vuswikoti bya acetylene oxidation eka Ni(OH)2 nanosheet catalyst leyi tolovelekeke (Ni(OH)2-NS) ya hunguteka, tani hileswi swi languteriweke, eka ti potentials tale henhla, kusuka eka 80% eka 1.5 VRHE kuya eka 42% eka 1.9 VRHE. Kuhambana swinene, endzhaku ko cinca Ni(OH)2 hi V, NiV-LDH-NS yi kombisile current density yale henhla eka potential leyi nyikiweke naswona, xa nkoka swinene, yi hlayise FE yale henhla eka potential range yo anama. Xikombiso, eka 1.9 VRHE, yi kombisile density ya sweswi ya 170 mA cm−2 na FE ya 83%, leyi nga catalyst leyinene swinene eka COR eka sisiteme ya ti electrode tinharhu (Fig. 1c na Tafula ro Engetela 1). Data ya swikambelo na ya thiyori yi kombisa leswaku ku cinciwa ka V ku tlakusa kinetics ya ku hunguta ku suka eka Ni(OH)2 ku ya eka high-valent Ni oxyhydroxides (Ni3+xOOH1-x), leyi tirhaka tanihi xiphemu lexi tirhaka xa COR. Ku tlula kwalaho, ku cinciwa ka V ku ndlandlamuxe ku adsorption ka cyclohexanone eka vuandlalo bya catalyst, leswi nga tlanga xiave xa nkoka eka ku tshikelela OER eka ti anodic potentials tale henhla. Ku kombisa vuswikoti bya NiV-LDH-NS eka xiyimo xa xiviri swinene, hi endlile reactor ya ku khuluka ka MEA naswona hi kombisile FE ya AA (82%) eka density ya sweswi leyi fambelanaka na tiindasitiri (300 mA cm−2), leyi nga ehenhla swinene ku tlula mbuyelo wa hina wa khale eka reactor ya ku khuluka ka membrane (Fig. 1b na Tafula ro Engetela 2). Mbuyelo lowu fambelanaka wa AA (1536 μmol cm−2 h−1) a wu ri ehenhla swinene ku tlula lowu kumiweke hi ku tirhisa endlelo ra thermal catalytic (<30 mmol gcatalyst−1 h−1)4. Kuya emahlweni, catalyst yikombe kutshamiseka kahle loko yitirhisiwa MEA, yi hlayisa FE >80% AA kuringana 60 h eka 200 mA cm−2 na FE >70% AA kuringana 58 h eka 300 mA cm−2. Eku heteleleni, dyondzo yosungula ya ku koteka (FEA) yi kombisile ku tirha kahle ka ntsengo wa maqhinga ya electrocatalytic eka vuhumelerisi bya AA.
Kuya hi matsalwa yale mahlweni, Ni(OH)2 i catalyst leyi tolovelekeke leyi kombisaka ntirho wa kahle eka COR, hikokwalaho Ni(OH)2-NS13,14 yi endliwile rosungula hiku tirhisa ndlela ya coprecipitation. Tisampulu ti kombisile xivumbeko xa β-Ni(OH)2, lexi tiyisisiweke hi X-ray diffraction (XRD; Fig. 2a), naswona ti ultra-thin nanosheets (ku enta: 2–3 nm, vukulu bya le tlhelo: 20–50 nm) ti langutiwile hi high-resolution transmission electron microscopy (HRTEM; Supplementary Fig. 1) na mipimo ya atomic force microscopy (AFM). (Xifaniso xo Engetela. 2). Ku hlengeletiwa ka ti nanosheets switlhele swivoniwa hikokwalaho ka ntumbuluko wa swona wa ultra-thin.
a swivumbeko swa ku hangalaka ka X-rheyi swa Ni(OH)2-NS na NiV-LDH-NS. FE, throughput, na AA current density eka b Ni(OH)2-NS na c NiV-LDH-NS eka ti potentials to hambana. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo ka mimpimo yinharhu leyi tiyimeleke hi ku tirhisa xihlohloteri xin’we. d Xifaniso xa HRTEM xa NV-LDH-NS. Bar ya xikalo: 20 nm. Xifaniso xa HAADF-STEM xa NiV-LDH-NS na mepe wa elemente lowu fambelanaka lowu kombisaka ku hangalaka ka Ni (rihlaza), V (yo tshwuka), na O (ya wasi). Bar ya xikalo: 100 nm. f Ni 2p3/2, g O 1 s, na h V 2p3/2 XPS data ya Ni(OH)2-NS (ehenhla) na NiV-LDH-NS (ehansi). i FE na j i matirhelo ya AA eka swihlohloteri swimbirhi eka 7 wa swirhendzevutani. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo ka mimpimo yinharhu leyi tiyimeleke hi ku tirhisa catalyst yin’we naswona ti le ndzeni ka 10%. Data ya raw ya a–c na f–j yi nyikiwile eka tifayela ta data ya raw.
Hiloko hi kambisisa vuyelo bya Ni(OH)2-NS eka COR. Hiku tirhisa constant potential electrolysis, hi kumile 80% FE ya AA eka potential yale hansi (1.5 VRHE) handle ka OER (Figure 2b), leswi kombisaka leswaku COR yi kahle swinene hi matimba kutlula OER eka ti anodic potentials tale hansi. Xiendliwa lexikulu xa by-product xikumeke xiri glutaric acid (GA) leyingana FE ya 3%. Kuva kona ka nhlayo ya trace ya succinic acid (SA), malonic acid (MA), na oxalic acid (OA) na swona swi pimiwile hi HPLC (vona Xifaniso xo Engetela xa 3 ku kuma ku hangalasiwa ka swikumiwa). Ku hava formic acid leyi kumiweke eka xiendliwa, leswi kombaka leswaku carbonate yinga vumbiwa tani hi C1 by-product. Ku kambela xiringanyeto lexi, electrolyte kusuka eka electrolysis leyi heleleke ya 0.4 M cyclohexanone yi endliwe acid naswona switirhisiwa swa gasi swi hundziseriwe eka Ca(OH)2 solution. Hikwalaho ka sweswo, solution yi hundzuke turbid, leswi tiyisekisaka ku vumbiwa ka carbonate endzhaku ka electrolysis. Hambiswiritano, hikokwalaho ka gezi hinkwaro ra le hansi leri endliwaka hi nkarhi wa endlelo ra electrolysis (Xifaniso 2b, c), nhlayo ya carbonate yile hansi naswona swa tika ku yi pima. Ku engetela kwalano, switirhisiwa swin’wana swa C2-C5 na swona swinga vumbiwa, kambe nhlayo ya swona ayi nge pimiwi. Hambi leswi nhlayo hinkwayo ya swikumiwa swi tikaka ku yi pima, 90% wa nhlayo hinkwayo ya electrochemical equivalent yi kombisa leswaku vunyingi bya maendlelo ya electrochemical ya tiviwile, leswi nyikaka xisekelo xa ku twisisa ka hina ka michini. Hikwalaho ka density yale hansi ya current (20 mA cm−2), mbuyelo wa AA akuri 97 μmol cm−2 h−1 (Xifaniso 2b), leswi ringanaka na 19 mmol h−1 g−1 kuya hi mass loading ya catalyst (5 mg cm−2), leswinga ehansi kutlula vuhumelerisi bya thermal catalytic (~30 mmol h−1 g−1)1. Loko potential leyi tirhisiweke yi tlakukile kusuka eka 1.5 kuya eka 1.9 VRHE, hambi leswi density ya current hinkwayo yi tlakukeke (kusuka eka 20 kuya eka 114 mA cm−2), hi nkarhi wun’we kuve na kuhunguteka lokukulu eka AA FE, kusuka eka 80% kuya eka 42%. Kuhunguteka ka FE eka ti potentials letinene ngopfu swivangiwa ngopfu hi mphikizano wa OER. Ngopfu ngopfu eka 1.7 VRHE, mphikizano wa OER wu yisa eka kuhunguteka lokukulu eka AA FE, hindlela yaleyo swihunguta nyana matirhelo ya AA hiku tlakuka ka density ya sweswi hinkwayo. Xisweswo, hambi leswi xiphemu xa current density ya AA yi tlakukeke kusuka eka 16 kuya eka 48 mA cm−2 naswona vuhumelerisi bya AA byi tlakukeke (kusuka eka 97 kuya eka 298 μmol cm−2 h−1), nhlayo leyikulu ya eneji yo engetelela yi tirhisiwile (2.5 W h gAA−1 more kusuka eka 1.5 kuya eka 1.9 VRHE), leswinga endla leswaku kuva na ku tlakuka ka carbon emissions ya 2.7 g CO2 gAA−1 (vuxokoxoko bya xibalo byi nyikiwile eka Xitsundzuxo xo Engetela xa 1). OER leyi xiyiweke khale tani hi muphikizani eka COR reaction eka ti anodic potentials tale henhla yi fambelana na swiviko swa khale naswona yi yimela ntlhontlho wo angarhela wo antswisa vuhumelerisi bya AA14,17.
Ku tumbuluxa xihlohloteri xa COR lexi tirhaka kahle swinene lexi simekiweke eka Ni(OH)2-NS, hi sungule hi ku xopaxopa xiphemu lexi tirhaka. Hi vonile tinhlohlorhi eka 473 cm-1 na 553 cm-1 eka mbuyelo wa hina wa in situ Raman spectroscopy (Xifaniso xo Engetela 4), leswi fambelanaka na ku gombonyoka na ku olovisiwa ka swihlanganisi swa Ni3+-O eka NiOOH, hi ku landzelelana. Ku tsariwile leswaku NiOOH i mbuyelo wa kuhunguteka ka Ni(OH)2 na ku hlengeletiwa ka Ni(OH)O eka ti anodic potentials, naswona hi xiviri i xiphemu lexi tirhaka eka electrocatalytic oxidation20,21. Hikwalaho, hi langutele leswaku ku hatlisisa endlelo ro pfuxeta xiphemu xa Ni(OH)2 ku ya eka NiOOH swi nga ndlandlamuxa ntirho wa catalytic wa COR.
Hi ringetile ku cinca Ni(OH)2 hi tinsimbi to hambana tani hileswi ku voniweke leswaku ku cinca ka heteroatom swi hlohletela ku akiwa nakambe ka xiphemu eka ti oxides/hydroxides ta nsimbi yo cinca22,23,24. Tisampulu ti endliwile hiku co-deposition ya Ni na precursor ya vumbirhi ya nsimbi. Exikarhi ka tisampulu to hambana leti cinciweke hi nsimbi, xikombiso lexi cinciweke hi V (V:Ni atomic ratio 1:8) (lexi vuriwaka NiV-LDH-NS) xi kombisile density yale henhla ya current eka COR (Supplementary Fig. 5) naswona xa nkoka swinene, AA FE yale henhla eka fasitere ro anama ra potential. Ngopfu ngopfu, eka potential yale hansi (1.5 VRHE), density ya sweswi ya NiV-LDH-NS ayi tlakukile hi 1.9 times kutlula ya Ni(OH)2-NS (39 vs. 20 mA cm−2), naswona AA FE ayi ringanisiwa eka ti catalysts leti hatimbirhi (83% vs. 80%). Hikwalaho ka density yale henhla ya current na FE AA leyi fanaka, vuhumelerisi bya NiV-LDH-NS byi tlakukile hi 2.1 times kutlula bya Ni(OH)2-NS (204 vs. 97 μmol cm−2 h−1), leswi kombisaka mbuyelo wo tlakusa wa V modification eka current density eka ti potentials tale hansi (Figure 2c).
Hiku tlakuka ka potential leyi tirhisiwaka (xikombiso, 1.9 VRHE), density ya sweswi eka NiV-LDH-NS yile henhla hi 1.5 times kutlula eka Ni(OH)2-NS (170 vs. 114 mA cm−2), naswona ku tlakuka swifana na leswinga eka ti potentials tale hansi (1.9 times higher). Lexi xiyekaka, NiV-LDH-NS yi hlayise AA FE yale henhla (83%) naswona OER yi tshikileriwile swinene (O2 FE 4%; Xifaniso 2c), yi tlula Ni(OH)2-NS naswona khale ka ti catalysts leti vikiweke letingana AA FE yale hansi swinene eka ti anodic potentials tale henhla (Supplementary Table 1). Hikwalaho ka FE yale henhla ya AA eka fasitere ro anama ra potential (1.5–1.9 VRHE), mpimo wa ku tumbuluxiwa ka AA wa 867 μmol cm−2 h−1 (lowu ringanaka na 174.3 mmol g−1 h−1) wu fikeleriwile eka 1.9 VRHE, leswi kombisaka matirhelo lamanene eka tisisiteme ta electrocatalytic hambi kuri thermocatalytic loko ntirho wu normalized hi total loading ya Tisampulu ta NiV-LDH-NS (Xifaniso xo Engetela. 6).
Ku twisisa density yale henhla ya current na FE yale henhla eka ndzhawu yo anama ya potential endzhaku ko cinca Ni(OH)2 hi V, hi hlamusele xivumbeko xa NiV-LDH-NS. Mbuyelo wa XRD wu kombisile leswaku ku cinciwa hi V swi vange ku cinca ka xiphemu kusuka eka β-Ni(OH)2 kuya eka α-Ni(OH)2, naswona akuri hava tinxaka ta crystalline leti fambelanaka na V leti kumiweke (Fig. 2a). Mbuyelo wa HRTEM wu kombisa leswaku NiV-LDH-NS yi dya ndzhaka ya xivumbeko xa ti ultrathin Ni(OH)2-NS nanosheets naswona yina ti dimensions ta le tlhelo leti fanaka (Fig. 2d). Mipimo ya AFM yi paluxe mboyamelo wo tiya wa nhlengeleto wa ti nanosheets, leswi endleke leswaku kuva na vukulu lebyi pimiwaka bya kwalomu ka 7 nm (Supplementary Fig. 7), lebyikulu kutlula bya Ni(OH)2-NS (ku enta: 2–3 nm). Nxopaxopo wa mepe wa energy-dispersive X-ray spectroscopy (EDS) (Xifaniso 2e) wu kombisile leswaku ti elements ta V na Ni ti hangalakile kahle eka ti nanosheets. Ku paluxa xivumbeko xa elektroniki xa V na vuyelo bya yona eka Ni, hi tirhise X-ray photoelectron spectroscopy (XPS) (Xifaniso 2f–h). Ni(OH)2-NS yi kombisile tinhlohlorhi ta xihlawulekisi xa spin-orbit ta Ni2+ (nhlohlorhi ya xisati eka 855.6 eV, nhlohlorhi ya sathelayiti eka 861.1 eV, Xifaniso 2f)25. O 1 s XPS spectrum ya Ni(OH)2-NS yinga avanyisiwa hi tinhlohlorhi tinharhu, exikarhi ka tona tinhlohlorhi eka 529.9, 530.9 na 532.8 eV ti vangiwa hi lattice oxygen (OL), hydroxyl group (Ni-OH) na oxygen adsorbed eka swihoxo swale henhla (OAds), hiku landzelelana (Xifaniso 2g)26,27,28,29. Endzhaku ka ku cinciwa hi V, nhlohlorhi ya V 2p3/2 yi humelerile, leyi nga bola kuva tinhlohlorhi tinharhu leti kumekaka eka 517.1 eV (V5+), 516.6 eV (V4+) na 515.8 eV (V3+), hiku landzelelana, leswi kombaka leswaku muxaka wa V eka xivumbeko ngopfu ngopfu wu kona eka swiyimo swa oxidation yale henhla (Xifaniso 2h)25,30,31. Ku engetela kwalano, nhlohlorhi ya Ni 2p eka 855.4 eV eka NiV-LDH-NS yi cinciwile hi ndlela yo biha (hi kwalomu ka 0.2 eV) loko ku pimanyisiwa na leyi nga eka Ni(OH)2-NS, leswi kombisaka leswaku ti electrons ti hundziseriwe kusuka eka V kuya eka Ni. Xiyimo xa valence xa le hansi swinene xa Ni lexi voniweke endzhaku ka ku cinciwa ka V a xi fambisana na mbuyelo wa Ni K-edge X-ray absorption near-edge spectroscopy (XANES) (vona xiyenge xa ​​“V Modification Promotes Catalyst Reduction” laha hansi ku kuma vuxokoxoko byo tala). NiV-LDH-NS endzhaku ka vutshunguri bya COR kuringana 1 h yi hlawuriwile tani hi NiV-LDH-POST naswona yi hlawuriwile hiku hetiseka hiku tirhisa transmission electron microscopy, EDS mapping, X-ray diffraction, Raman spectroscopy, na mimpimo ya XPS (Swifaniso swo Engetela. 8 na 9). Ti catalysts ti tshamile tani hi ti aggregates letingana ultrathin nanosheet morphology (Xifaniso xo Engetela. 8a–c). Crystallinity ya tisampulu yi hungutekile naswona nhlayo ya V yihunguteke hikokwalaho ka V leaching na catalyst reconstruction (Supplementary Fig. 8d–f). Ti spectra ta XPS ti kombisile kuhunguteka ka matimba ya nhlohlorhi ya V (Supplementary Fig. 9), leswinga vangiwa hi V leaching. Ku engetela kwalaho, nxopaxopo wa O 1s spectrum (Xifaniso xo Engetela. 9d) na mimpimo ya electron paramagnetic resonance (EPR) (Xifaniso xo Engetela. 10) swi kombisile leswaku nhlayo ya swivandla swa okisijini eka NiV-LDH-NS yi engetelekile endzhaku ka 1 h ya electrolysis, leswi nga tisaka ku cinca loku nga riki kunene eka matimba yo boha ya Ni 2p (vona Swifaniso swo Engetela. 9 na 10 ku kuma swo tala vuxokoxoko)26,27,32,33. Xisweswo, NiV-LDH-NS yi kombisile ku cinca kutsongo ka xivumbeko endzhaku ka 1 h ya COR.
Ku tiyisisa ntirho wa nkoka wa V eka ku tlakusa COR, hi hlanganisile ti NiV-LDH catalysts letingana ti V:Ni atomic ratios tohambana hambana (1:32, 1:16, na 1:4, leti hlawuriweke tani hi NiV-32, NiV-16, na NiV-4, hiku landzelelana) handle ka 1:8 hi ndlela leyi fanaka ya coprecipitation. Mbuyelo wa EDS mapping wu kombisa leswaku V:Ni atomic ratio eka catalyst yi le kusuhi na ya precursor (Supplementary Fig. 11a–e). Hiku tlakuka ka ku cinca ka V, matimba ya V 2p spectrum ya tlakuka, naswona matimba yo boha ya ndzhawu ya Ni 2p ya ya emahlweni ya cincela eka tlhelo ro biha (Xifaniso xo Engetela. 12). Hi nkarhi lowu fanaka, xiphemu xa OL xi andzile hakatsongo-tsongo. Mbuyelo wa xikambelo xa catalytic wukombisa leswaku OER yinga tshikileriwa hindlela leyinene hambi endzhaku ka ku cinciwa ka V lokuntsongo (V:Ni atomic ratio ya 1:32), laha O2 FE yihungutekaka kusuka eka 27% kuya eka 11% eka 1.8 VRHE endzhaku ka ku cinciwa ka V (Xifaniso xo Engetela. 11f). Hiku tlakuka ka V:Ni ratio kusuka eka 1:32 kuya eka 1:8, ntirho wa catalytic wu tlakukile. Hambiswiritano, hi ku engeteleka kun’wana ka ku cinca ka V (V:Ni ratio ya 1:4), density ya sweswi ya hunguteka, leswi hi ehleketaka leswaku swi vangiwa hi ku hunguteka ka density ya tindhawu leti tirhaka ta Ni (ngopfu-ngopfu xiphemu lexi tirhaka xa NiOOH; Supplementary Fig. 11f). Hikwalaho ka mbuyelo wo tlakusa wa ku cinca ka V xikan’we naku hlayisiwa ka tindzhawu leti tirhaka ta Ni, catalyst leyingana V:Ni ratio ya 1:8 yikombe matirhelo yale henhla swinene ya FE na AA eka xikambelo xa V:Ni ratio screening. Ku endlela ku hlamusela loko V:Ni ratio yitshama yirikarhi yi cinca cinca endzhaku ka electrolysis, xivumbeko xa ti catalysts leti tirhisiweke xi hlamuseriwile. Mbuyelo wukombisa leswaku eka ti catalysts letingana ti V:Ni ratios tosungula kusuka eka 1:16 kuya eka 1:4, V:Ni ratio yi hungutekile kuya kwalomu ka 1:22 endzhaku ka reaction, leswingava swivangiwa hi leaching ya V hikokwalaho ka catalyst reconstruction (Supplementary Fig. 13). Xiya leswaku ti AA FEs leti ringanisiwaka ti voniwile loko V:Ni ratio yosungula yi ringana kumbe e henhla kutlula 1:16 (Supplementary Fig. 11f), leswinga hlamuseriwa hiku akiwa nakambe ka catalyst leswinga endla leswaku kuva na ti ratios ta V:Ni leti fanaka eka ti catalysts leti kombisaka matirhelo ya catalytic lawa ya ringanisiwaka.
Ku ya emahlweni hi tiyisisa nkoka wa V-modified Ni(OH)2 eka ku ndlandlamuxa matirhelo ya COR, hi tumbuluxile tindlela tin’wana timbirhi ta synthetic ku nghenisa V eka switirhisiwa swa Ni(OH)2-NS. Yin’wana i ndlela yo hlanganisa, naswona xikombiso xi vuriwa NiV-MIX; yin’wana i ndlela ya sequential sputtering, naswona xikombiso xi vuriwa NiV-SP. Vuxokoxoko bya nkatsakanyo byi nyikiwile eka xiyenge xa ​​Maendlelo. SEM-EDS mapping yi kombisile leswaku V yi cinciwile hi ndlela leyi humelelaka eka Ni(OH)2-NS surface ya tisampulu leti hatimbirhi (Supplementary Fig. 14). Mbuyelo wa electrolysis wukombisa leswaku eka 1.8 VRHE, AA efficiency eka NiV-MIX na NiV-SP electrodes i 78% na 79%, hiku landzelelana, hinkwaswo swikombisa vukorhokeri byale henhla kutlula Ni(OH)2-NS (51%). Ku tlula kwalaho, OER eka ti electrode ta NiV-MIX na NiV-SP yi tshikileriwile (FE O2: 7% na 2%, hi ku landzelelana) loko ku pimanisiwa na Ni(OH)2-NS (FE O2: 27%). Mimbuyelo leyi yi tiyisisa mbuyelo lowunene wa ku cinca ka V eka Ni(OH)2 eka ku tshikileriwa ka OER (Xifaniso xo Engetela. 14). Hambiswiritano, kutshamiseka ka ti catalysts swinga onhiwa, leswinga kombisiwa hiku hunguteka ka FE AA eka NiV-MIX kuya eka 45% nale ka NiV-SP kuya eka 35% endzhaku ka nkombo wa swirhendzevutani swa COR, leswi vulaka xilaveko xo amukela tindlela leti faneleke ku tiyisisa tinxaka ta V, kufana na ku cinciwa ka V eka Ni(OH)2 lattice eka NiV-LDH-NS, leyi kunga catalyst ya nkoka eka leswi ntirho.
Hi tlhele hi kambela ku tshamiseka ka Ni(OH)2-NS na NiV-LDH-NS hi ku veka COR eka swirhendzevutani swo tala. Ku cinca cinca ku endliwile kuringana 1 h hi xirhendzevutani naswona electrolyte yi cinciwile endzhaku ka xirhendzevutani xin’wana na xin’wana. Endzhaku ka xirhendzevutani xa vu 7, matirhelo ya FE na AA eka Ni(OH)2-NS ya hungutekile hi 50% na 60%, hi ku landzelelana, kasi ku tlakuka ka OER ku voniwile (Fig. 2i, j). Endzhaku ka xirhendzevutani xin’wana na xin’wana, hi kambisisile ti cyclic voltammetry (CV) curves ta ti catalysts naswona hi xiye leswaku nhlohlorhi ya oxidation ya Ni2+ yi hungutekile hakatsongotsongo, leswi kombisaka ku hunguteka ka vuswikoti bya redox bya Ni (Supplementary Fig. 15a–c). Xikan’we na ku tlakuka ka nhlayo ya Ni cation eka electrolyte hi nkarhi wa electrolysis (Xifaniso xo Engetela. 15d), hi vula leswaku ku onhaka ka matirhelo (ku hunguteka ka vuhumelerisi bya FE na AA) ku vangiwa hi ku khuluka ka Ni ku suka eka catalyst, leswi endlaka leswaku ku va na ku paluxiwa lokukulu ka substrate ya Ni foamed leyi kombisaka ntirho wa OER. Kuhambana na sweswo, NiV-LDH-NS yi hungute kuhunguteka ka vuhumelerisi bya FE na AA kuya eka 10% (Fig. 2i, j), leswi kombaka leswaku ku cinciwa ka V swisivele kahle ku khuluka ka Ni (Xifaniso xo Engetela. 15d). Ku twisisa ku tshamiseka loku antswisiweke ka ku cinciwa ka V, hi endlile swibalo swa thiyori. Hi ku ya hi matsalwa ya khale34,35, ku cinca ka enthalpy ya endlelo ra demetalization ra tiatomo ta nsimbi eka vuandlalo lebyi tirhaka bya xihlohloteri ku nga tirhisiwa tanihi nhlamuselo leyi twalaka ku kambela ku tshamiseka ka xihlohloteri. Hikwalaho, ku cinca ka enthalpy ka endlelo ra demetalization ra tiatomo ta Ni eka (100) vuandlalo bya Ni(OH)2-NS na NiV-LDH-NS leyi pfuxetiweke (NiOOH na NiVOOH, hi ku landzelelana) ku ringanyetiwe (vuxokoxoko bya ku akiwa ka modele byi hlamuseriwile eka Xitsundzuxo xo Engetela xa 2 na Xifaniso xo Engetela xa 16). Endlelo ra demetalization ra Ni kusuka eka NiOOH na NiVOOH ri kombisiwile (Xifaniso xo Engetela. 17). Ntsengo wa eneji ya Ni demetallization eka NiVOOH (0.0325 eV) wule henhla kutlula eka NiOOH (0.0005 eV), leswi kombaka leswaku ku cinciwa ka V swi tlakusa ku tshamiseka ka NiOOH.
Ku tiyisisa mbuyelo wa OER inhibitory eka NiV-LDH-NS, ngopfu ngopfu eka ti anodic potentials tale henhla, differential electrochemical mass spectrometry (DEMS) yi endliwile ku lavisisa ku tumbuluxiwa ka O2 leyi titshegeke hi vuswikoti eka tisampulu to hambana. Mimbuyelo yi kombisile leswaku eka ku pfumaleka ka cyclohexanone, O2 eka NiV-LDH-NS yi humelerile eka vuswikoti byo sungula bya 1.53 VRHE, leyi a yi ri ehansi nyana ku tlula ya O2 eka Ni(OH)2-NS (1.62 VRHE) (Xifaniso xo Engetela. 18). Mbuyelo lowu wu ringanyeta leswaku ku sivela ka OER ka NiV-LDH-NS hi nkarhi wa COR ku nga ha va ku nga ri hikwalaho ka ntirho wa yona wa le hansi wa OER, leswi fambelanaka na density ya current leyi tlakukeke nyana eka ti curves ta linear sweep voltammetry (LSV) eka NiV-LDH-NS ku tlula eka Ni(OH)2-NS handle ka cyclohexanone (Xifaniso xo Engetela. 19). Endzhaku ka ku nghenisiwa ka cyclohexanone, ku hlwela ka O2 evolution (swinga endleka hikokwalaho ka thermodynamic advantage ya COR) swi hlamusela FE yale henhla ya AA eka ndzhawu ya low potential. Xa nkoka swinene, vuswikoti byo sungula bya OER eka NiV-LDH-NS (1.73 VRHE) byi hlwela ku tlula lebyi nga eka Ni(OH)2-NS (1.65 VRHE), leswi fambelanaka na FE ya le henhla ya AA na FE ya le hansi ya O2 eka NiV-LDH-NS eka vuswikoti byo antswa swinene (Xifaniso 2c).
Ku ya emahlweni hi twisisa mbuyelo wo tlakusa wa ku cinca ka V, hi kambisisile OER na COR reaction kinetics eka Ni(OH)2-NS na NiV-LDH-NS hi ku pima swirhendzevutani swa vona swa Tafel. Swifanele ku xiya leswaku density ya sweswi eka ndzhawu ya Tafel yivangiwa hi oxidation ya Ni2+ kuya eka Ni3+ hinkarhi wa xikambelo xa LSV kusuka eka potential yale hansi kuya eka potential yale henhla. Ku hunguta mbuyelo wa Ni2+ oxidation eka COR Tafel slope measurement, hi sungule hi oxidized catalyst eka 1.8 VRHE kuringana 10 min kutani hi endla swikambelo swa LSV eka reverse scan mode, i.e., kusuka eka high potential kuya eka low potential (Supplementary Fig. 20). Curve ya LSV yosungula yi lulamisiwile hi 100% iR compensation kuva ku kumiwa Tafel slope. Eka ku pfumaleka ka cyclohexanone, Tafel slope ya NiV-LDH-NS (41.6 mV dec−1) a yi ri ehansi ku tlula ya Ni(OH)2-NS (65.5 mV dec−1), leswi kombisaka leswaku OER kinetics yi nga antswisiwa hi ku cinciwa ka V (Xifaniso xo Engetela. 20c). Endzhaku ka ku nghenisiwa ka cyclohexanone, Tafel slope ya NiV-LDH-NS (37.3 mV dec−1) a yi ri ehansi ku tlula ya Ni(OH)2-NS (127.4 mV dec−1), leswi kombisaka leswaku ku cinciwa ka V a ku ri na mbuyelo wa kinetic lowu nga erivaleni swinene eka COR loko ku pimanisiwa na OER (Xifaniso xo Engetela. 20d). Mimbuyelo leyi yi ringanyeta leswaku hambi leswi ku cinciwa ka V ku tlakusaka OER ku fika eka mpimo wo karhi, swi hatlisisa swinene COR kinetics, leswi endlaka leswaku ku va na ku tlakuka ka FE ya AA.
Ku kota ku twisisa mbuyelo wo tlakusa wa ku cinca ka V loku nga laha henhla eka matirhelo ya FE na AA, hi kongomise eka dyondzo ya endlelo. Swiviko swin’wana swa khale swi kombisile leswaku ku cinciwa ka heteroatom swi nga hunguta crystallinity ya ti catalysts na ku engetela ndhawu ya le henhla leyi tirhaka hi electrochemically (EAS), hi ndlela yoleyo ku engetela nhlayo ya tindhawu leti tirhaka xisweswo ku antswisa ntirho wa catalytic36,37. Ku lavisisa ku koteka loku, hi endlile mimpimo ya ECSA emahlweni na le ndzhaku ka ku tirhisiwa ka electrochemical, naswona mbuyelo wu kombisile leswaku ECSA ya Ni(OH)2-NS na NiV-LDH-NS a yi ringanisiwa (Xifaniso xo Engetela. 21), ku nga katsiwi nkucetelo wa ku tsindziyela ka ndhawu leyi tirhaka endzhaku ka ku cinciwa ka V eka ku antswisiwa ka catalytic.
Hikuya hi vutivi lebyi amukeriwaka hiku angarhela, eka Ni(OH)2-catalyzed electrooxidation ya ti alcohols kumbe ti nucleophilic substrates tin’wana, Ni(OH)2 yisungula yi lahlekeriwa hi ti electrons na ti protons kutani yihungutiwa kuya eka NiOOH hiku tirhisa magoza ya electrochemical eka anodic potential yokarhi38,39,40,41. NiOOH leyi vumbiweke yitlhela yi tirha tani hi muxaka wa COR lowu tirhaka wa xiviri ku humesa hayidirojeni na tielektroni kusuka eka substrate ya nucleophilic hiku tirhisa magoza ya tikhemikhali ku vumba xiendliwa lexi oxidized20,41. Hambiswiritano, sweswinyana swivikiwile leswaku hambi leswi kuhungutiwa kuya eka NiOOH swinga tirha tani hi goza leri vekaka mpimo (RDS) ra electrooxidation ya byala eka Ni(OH)2, tani hileswi swiringanyetiweke eka matsalwa ya sweswinyana, oxidation ya Ni3+ alcohols yingava endlelo ro tisungulela hiku tirhisa non-redox electron transfer hiku tirhisa ti orbitals letinga tshamiki ta Ni3+41,42. Hi ku hlohloteriwa hi dyondzo ya michini leyi vikiweke eka matsalwa lama fanaka, hi tirhise dimethylglyoxime disodium salt octahydrate (C4H6N2Na2O2 8H2O) tanihi molekhuli ya probe ku khoma in situ ku tumbuluxiwa kwihi na kwihi ka Ni2+ loku vangiwaka hi ku hunguteka ka Ni3+ hi nkarhi wa COR (Xifaniso xo Engetela. 22 na Xitsundzuxo xo Engetela 3). Mbuyelo wu kombisile ku vumbiwa ka Ni2+, leswi tiyisisaka leswaku kuhungutiwa ka ti khemikhali ta NiOOH na electrooxidation ya Ni(OH)2 swihumelerile hi nkarhi wun’we hi nkarhi wa maendlelo ya COR. Hikokwalaho, ntirho wa catalytic wunga titshega swinene hi kinetics ya Ni(OH)2 reduction kuya eka NiOOH. Hi ku ya hi nsinya lowu, hi landzerile hi lavisisa loko ku cinciwa ka V ku ta hatlisisa ku hunguteka ka Ni(OH)2 xisweswo ku antswisa COR.
Hi sungule hi tirhisa tithekiniki ta Raman ta in situ ku kombisa leswaku NiOOH i xiphemu lexi tirhaka xa COR eka Ni(OH)2-NS na NiV-LDH-NS hi ku languta ku vumbiwa ka NiOOH eka ti potentials letinene na ku tirhisiwa ka yona loku landzelaka endzhaku ka ku nghenisiwa ka cyclohexanone, ku landzela endlelo leri boxiweke laha henhla ra “electrochemical-chemical” (Xifaniso 3a). Ku tlula kwalaho, ku angula ka NiV-LDH-NS leyi pfuxetiweke ku tlula ya Ni(OH)2-NS, tanihilaha swi kombisiweke hakona hi ku hatlisa ku nyamalala ka xikombiso xa Ni3+–O Raman. Hiloko hi kombisa leswaku NiV-LDH-NS yi kombisile vuswikoti lebyi nga riki byinene bya ku tumbuluxiwa ka NiOOH loko ku pimanisiwa na Ni(OH)2-NS eka vukona kumbe ku pfumaleka ka cyclohexanone (Xifaniso 3b, c na Xifaniso xo Engetela. 4c, d). Lexi xiyekaka, matirhelo yale henhla ya OER ya NiV-LDH-NS ya endla leswaku kuva na swiphemuphemu swotala leswi namarhelaka eka lens yale mahlweni ya xikongomelo xa mpimo wa Raman, leswi endlaka leswaku nhlohlorhi ya Raman eka 1.55 VRHE yi nyamalala (Xifaniso xo Engetela. 4d). Kuya hi mbuyelo wa DEMS (Supplementary Fig. 18), density ya sweswi eka ti potentials tale hansi (VRHE < 1.58 eka Ni(OH)2-NS na VRHE < 1.53 eka NiV-LDH-NS) ngopfu ngopfu swivangiwa hiku pfuxetiwa ka ti ions ta Ni2+ kutlula OER eka ku pfumaleka ka cyclohexanone. Xisweswo, nhlohlorhi ya oxidation ya Ni2+ eka LSV curve yi tiyile ku tlula ya NiV-LDH-NS, leswi kombisaka leswaku ku cinciwa ka V ku nyika NiV-LDH-NS vuswikoti byo antswisiwa bya remodeling (vona Xifaniso xo Engetela xa 19 ku kuma nxopaxopo wa vuxokoxoko).
a In situ Raman spectra ya Ni(OH)2-NS (exineneni) na NiV-LDH-NS (exineneni) ehansi ka swiyimo swa OCP endzhaku ka preoxidation eka 1.5 VRHE eka 0.5 M KOH na 0.4 M cyclohexanone kuringana 60 s. b In situ Raman spectra ya Ni(OH)2-NS na c NiV-LDH-NS eka 0.5 M KOH + 0.4 M cyclohexanone eka ti potentials to hambana. d In situ XANES spectra ya Ni(OH)2-NS na NiV-LDH-NS eka Ni K-edge eka 0.5 M KOH na e 0.5 M KOH na 0.4 M cyclohexanone. Inset yikombisa ndzhawu ya spectral leyi kurisiweke exikarhi ka 8342 na 8446 eV. f Swiyimo swa valence swa Ni eka Ni(OH)2-NS na NiV-LDH-NS eka ti potentials to hambana. g In situ Ni EXAFS spectra ya NiV-LDH-NS emahlweni na le ndzhaku ka ku nghenisiwa ka cyclohexanone eka ti potentials to hambana. h Timodelo ta thiyori ta Ni(OH)2-NS na NiV-LDH-NS. Ehenhla: Eka Ni(OH)2-NS, ku pfuxetiwa ka xihatla kusuka eka Ni(OH)2-NS kuya eka NiOOH switirha tani hi RDS, kasi cyclohexanone yi hunguta tinxaka ta Ni ta high-valent hiku tirhisa magoza ya ti khemikhali kuva yi hlayisa xiyimo xa low-valent Ni kuva yi humesa AA. Ehansi: Eka NiV-LDH-NS, goza ro pfuxeta ri fambisiwa hi ku cinciwa ka V, leswi endlaka leswaku ku hundziseriwa RDS ku suka eka goza ro pfuxeta ku ya eka goza ra tikhemikhali. i Eneji ya mahala ya Gibbs ya cinca eka ku akiwa nakambe ka Ni(OH)2-NS na NiV-LDH-NS. Data ya raw ya aj na i yi nyikiwile eka fayili ya data ya raw.
Ku lavisisa ku hundzuka ka swivumbeko swa athomo na swa elektroniki hi nkarhi wa ku hungutiwa ka catalyst, hi endlile swikambelo swa in situ X-ray absorption spectroscopy (XAS), leswi nyikeke xitirhisiwa xa matimba xo lavisisa dynamics ya tinxaka ta Ni eka magoza manharhu lama landzelelanaka: OER, cyclohexanone injection, na COR eka open circuit potential (OCP). Xifaniso xi kombisa K-edge XANES spectra ya Ni leyi nga na vuswikoti lebyi engetelekaka emahlweni na le ndzhaku ka ku cheriwa ka cyclohexanone (Xifaniso 3d, e). Eka potential leyi fanaka, absorption edge energy ya NiV-LDH-NS yi kahle swinene kutlula ya Ni(OH)2-NS (Xifaniso 3d, e, inset). Valence ya xikarhi ya Ni ehansi ka xiyimo xin’wana na xin’wana yi ringanyetiwe hi linear combined fit ya XANES spectra na regression ya Ni K-edge absorption energy shift (Xifaniso 3f), na reference spectrum leyi tekiweke eka matsalwa lama kandziyisiweke (Supplementary Fig. 23)43.
Eka goza rosungula (emahlweni ka ku nghenisiwa ka cyclohexanone, leyi fambelanaka na endlelo ra OER; Xifaniso 3f, eximatsini), eka vuswikoti bya catalyst leyi nga endliwangiki nakambe (<1.3 VRHE), xiyimo xa valence xa Ni eka NiV-LDH-NS (+1.83) xile hansi nyana kutlula xa Ni(OH)2-NS (+1.97), leswinga vangiwa hiku hundziseriwa ka ti electron kusuka eka V kuya eka Ni, leswi fambelanaka na mbuyelo wa XPS lowu boxiweke laha henhla (Xifaniso 2f). Loko potential yi tlula reduction point (1.5 VRHE), xiyimo xa valence xa Ni eka NiV-LDH-NS (+3.28) xikombisa ku tlakuka loku vonakaka swinene loko ku pimanyisiwa na xa Ni(OH)2-NS (+2.49). Eka potential yale henhla (1.8 VRHE), xiyimo xa valence xa ti particles ta Ni leti kumiweke eka NiV-LDH-NS (+3.64) xile henhla kutlula xa Ni(OH)2-NS (+3.47). Kuya hi swiviko swa sweswinyana, endlelo leri ri fambelana na ku vumbiwa ka tinxaka ta Ni4+ ta high-valent eka xivumbeko xa Ni3+xOOH1-x (Ni3+x i muxaka lowu pfanganisiweke wa Ni3+ na Ni4+), leswi khale swi kombiseke ku antswisiwa ka ntirho wa catalytic eka alcohol dehydrogenation38,39,44. Hikokwalaho, matirhelo yale henhla ya NiV-LDH-NS eka COR yangava hikokwalaho ka kuhunguteka loku antswisiweke kuva ku vumba tinxaka ta Ni ta high-valent leti tirhaka hi catalytically.
Eka goza ra vumbirhi (ku nghenisiwa ka cyclohexanone endzhaku ka ku pfuriwa ka ring, Xifaniso 3f), xiyimo xa valence xa Ni eka ti catalysts leti hatimbirhi xi hungutekile swinene, leswi fambelanaka na endlelo ro hunguta ra Ni3+xOOH1-x hi cyclohexanone, leswi fambelanaka na mbuyelo wa in situ Raman spectroscopy (Xifaniso 3a), naswona xiyimo xa valence xa Ni xi lava ku vuyelela eka xiyimo xo sungula (goza ro sungula eka potential yale hansi), leswi kombisaka ku tlheriseriwa endzhaku ka endlelo ra redox ra Ni kuya eka Ni3+xOOH1-x.
Eka goza ra vunharhu (COR process) eka ti COR potentials (1.5 na 1.8 VRHE; Xifaniso 3f, exineneni), xiyimo xa valence xa Ni eka Ni(OH)2-NS xi tlakuke nyana ntsena (+2.16 na +2.40), leswi nga ehansi swinene ku tlula eka potential yin’we eka goza ro sungula (+2.49 na +3.47). Mimbuyelo leyi yi kombisa leswaku endzhaku ka ku cheriwa ka cyclohexanone, COR yi pimiwile hi ndlela ya kinetically hi oxidation yo nonoka ya Ni2+ kuya eka Ni3+x (i.e., Ni reconstruction) kutlula hi goza ra tikhemikhali exikarhi ka NiOOH na cyclohexanone eka Ni(OH)2-NS, leswi siyaka Ni eka xiyimo xa low-valence. Xisweswo, hi gimeta hi leswaku ku pfuxetiwa ka Ni ku nga tirha tanihi RDS eka endlelo ra COR eka Ni(OH)2-NS. Kuhambana na sweswo, NiV-LDH-NS yi hlayise valence yale henhla swinene ya tinxaka ta Ni (>3) hinkarhi wa maendlelo ya COR, naswona valence yihunguteke ehansi swinene (ehansi ka 0.2) loko ku pimanyisiwa na goza rosungula eka potential leyi fanaka (1.65 na 1.8 VRHE), leswi kombaka leswaku ku cinca ka V hi kinetically swi hlohlotele oxidation ya Ni2+ kuya eka Ni3+x, leswi endlaka leswaku endlelo ro hunguta Ni ri hatlisa ku tlula goza ra tikhemikhali ra ku hunguta cyclohexanone. Mbuyelo wa extended X-ray absorption fine structure (EXAFS) wutlhele wu paluxa ku cinca loku heleleke ka Ni–O (kusuka eka 1.6 kuya eka 1.4 Å) na Ni–Ni(V) (kusuka eka 2.8 kuya eka 2.4 Å) bonds eka vukona bya cyclohexanone. Leswi swi fambisana na ku pfuxetiwa ka xiphemu xa Ni(OH)2 ku ya eka xiphemu xa NiOOH na ku hungutiwa ka tikhemikhali ta xiphemu xa NiOOH hi cyclohexanone (Fig. 3g). Hambiswiritano, cyclohexanone yi sive swinene reduction kinetics ya Ni(OH)2-NS (vona Supplementary Note 4 na Supplementary Fig. 24 ku kuma vuxokoxoko byo tala).
Hi ku angarhela, eka Ni(OH)2-NS (Fig. 3h, ehenhla), goza ro hunguta hi ku nonoka ku suka eka xiphemu xa Ni(OH)2 ku ya eka xiphemu xa NiOOH ri nga tirha tanihi RDS ya endlelo hinkwaro ra COR ku tlula goza ra tikhemikhali ra ku tumbuluxiwa ka AA ku suka eka cyclohexanone hi nkarhi wa ku hungutiwa ka tikhemikhali ta NiOOH. Eka NiV-LDH-NS (Fig. 3h, ehansi), ku cinciwa ka V ku ndlandlamuxa oxidation kinetics ya Ni2+ kuya eka Ni3+x, hindlela yaleyo ku hatlisisa ku tumbuluxiwa ka NiVOOH (ku tlula ku tirhisiwa hiku hunguta ti khemikhali), leswi cincaka RDS kuya eka goza ra ti khemikhali. Ku twisisa ku pfuxetiwa ka Ni loku hlohloteriweke hi ku cinciwa ka V, hi endlile swibalo swin’wana swa thiyori. Hilaha swi kombisiweke hakona eka Fig. 3h, hi tekelele endlelo ro aka hi vuntshwa ra Ni(OH)2-NS na NiV-LDH-NS. Mintlawa ya lattice hydroxyl eka Ni(OH)2-NS na NiV-LDH-NS yi deprotonated hiku humesa OH- eka electrolyte kuva yi endla electron-deficient lattice oxygen. Ku cinca ka tikhemikhali loku fambelanaka na kona hi loku landzelaka:
Ku cinca ka eneji ya mahala ya Gibbs ya ku pfuxetiwa ku hlayiwile (Xifaniso 3i), naswona NiV-LDH-NS (0.81 eV) yi kombisile ku cinca ka eneji ya mahala ya Gibbs leyintsongo swinene ku tlula Ni(OH)2-NS (1.66 eV), leswi kombisaka leswaku ku cinciwa ka V ku hungute voltage leyi lavekaka eka ku pfuxetiwa ka Ni. Hi tshemba leswaku ku tlakusa ku pfuxetiwa swi nga hunguta xisirhelelo xa eneji xa COR hinkwayo (vona dyondzo ya endlelo ra ku angula laha hansi ku kuma vuxokoxoko), hi ndlela yaleyo ku hatlisisa ku cinca eka ti densities tale henhla ta current.
Nxopaxopo lowu nga laha henhla wu kombisa leswaku ku cinciwa ka V swivanga ku lulamisiwa nakambe ka phase hiku hatlisa ka Ni(OH)2, hindlela yaleyo ku engetela mpimo wa reaction naswona, hiku famba ka nkarhi, COR current density. Hambiswiritano, tindzhawu ta Ni3+x tinga tlhela ti tlakusa ntirho wa OER. Kusuka eka LSV curve leyinga hava cyclohexanone, swile rivaleni leswaku density ya sweswi ya NiV-LDH-NS yile henhla kutlula ya Ni(OH)2-NS (Supplementary Fig. 19), leswi endlaka leswaku ti COR na OER reactions ti vumba ti competitive reactions. Hikokwalaho, FE yale henhla swinene ya AA kutlula ya NiV-LDH-NS ayi hlamuseriwa hiku hetiseka hi ku cinca ka V loku hlohlotelaka ku lulamisiwa nakambe ka xiphemu.
Hi ntolovelo swi amukeriwa leswaku eka alkaline media, ti electrooxidation reactions ta ti nucleophilic substrates hi ntolovelo ti landzelela modele wa Langmuir–Hinshelwood (LH). Hiku kongoma, substrate na OH− anions swi phikizana coadsorbed eka catalyst surface, naswona OH− leyi adsorbed yi oxidized kuya eka active hydroxyl groups (OH*), leyi tirhaka tani hi electrophiles eka oxidation ya nucleophiles, endlelo leri khale ri kombisiweke hi data ya experimental na/kumbe swibalo swa theoretical45,46,47. Xisweswo, nhlayo ya ti reactants na ratio ya tona (organic substrate na OH−) swinga lawula ku funengetiwa ka reactant ya catalyst surface, hindlela yaleyo swi khumba FE na mbuyelo wa xiendliwa lexi kongomisiweke14,48,49,50. Eka hina, hi ehleketa leswaku ku funengetiwa ka le henhla ka cyclohexanone eka NiV-LDH-NS ku tsakela endlelo ra COR, naswona hi ndlela yo hambana, ku funengetiwa ka le henhla ka cyclohexanone eka Ni(OH)2-NS ku tsakela endlelo ra OER.
Ku kambela xiringanyeto lexi nga laha henhla, hi sungule hi ku endla nxaxamelo wa swikambelo swimbirhi leswi fambelanaka na nhlayo ya swiaki leswi cinca-cincaka (C, cyclohexanone, na COH−). Xikambelo xosungula xi endliwile hi electrolysis eka constant potential (1.8 VRHE) eka Ni(OH)2-NS na NiV-LDH-NS catalysts leswingana cyclohexanone C yohambana hambana (0.05 ~ 0.45 M) na fixed COH− content (0.5 M). Kutani, vuhumelerisi bya FE na AA byi hlayiwile. Eka NiV-LDH-NS catalyst, vuxaka exikarhi ka mbuyelo wa AA na cyclohexanone C byi kombisile curve yo tolovelekile ya “volcanic type” eka movha wa LH (Fig. 4a), leswi kombisaka leswaku ku funengetiwa ka cyclohexanone lokukulu ku phikizana na OH− adsorption. Loko eka Ni(OH)2-NS, mbuyelo wa AA wu tlakuke hi ndlela ya monotonically hiku tlakuka ka C ya cyclohexanone kusuka eka 0.05 kuya eka 0.45 M, leswi kombaka leswaku hambi leswi nhlayo ya bulk ya cyclohexanone ayi ri e henhla (0.45 M), ku funengetiwa ka yona ka le henhla ka ha ri ehansi swinene. Ku engetela kwalaho, hi ku tlakuka ka COH− ku ya eka 1.5 M, curve ya “volcanic type” yi voniwile eka Ni(OH)2-NS ku ya hi C ya cyclohexanone, naswona inflection point ya matirhelo yi hlwerile loko yi pimanisiwa na NiV-LDH-NS, leswi yaka emahlweni swi kombisa ku tsana ka adsorption ya cyclohexanone eka Ni(OH)2-NS (Supplementary Fig. 25a na Note 5). Ku engetela kwalaho, FE ya AA eka NiV-LDH-NS a yi ri na vuxiyaxiya swinene eka C-cyclohexanone naswona yi tlakuke hi ku hatlisa ku tlula 80% loko C-cyclohexanone yi engeteriwile ku suka eka 0.05 M ku ya eka 0.3 M, leswi kombisaka leswaku cyclohexanone yi fuwile hi ku olova eka NiV-LDH-NS (Xifaniso 4b). Kuhambana na sweswo, ku engetela nhlayo ya C-cyclohexanone aswi sivela swinene OER eka Ni(OH)2-NS, leswinga vangiwa hiku pfumaleka ka adsorption ya cyclohexanone. Hi ndlela yo hambana, vulavisisi byin’wana bya ku titshega ka COH− eka vuswikoti bya catalytic byi tlhele byi tiyisisa leswaku ku adsorption ka cyclohexanone ku antswisiwile loko ku pimanisiwa na NiV-LDH-NS, leyi nga tiyiselaka COH− ya le henhla hi nkarhi wa endlelo ra COR handle ko hunguta FE ya AA (Xifaniso xo Engetela. 25b, c na Xitsundzuxo 5).
Vuhumelerisi bya AA na EF ya b Ni(OH)2-NS na NiV-LDH-NS eka cyclohexanone na C yo hambana eka 0.5 M KOH. c Eneji ya adsorption ya cyclohexanone eka NiOOH na NiVOOH. d FE ya AA eka Ni(OH)2-NS na NiV-LDH-NS eka 0.5 M KOH na 0.4 M cyclohexanone eka 1.80 VRHE hi ku tirhisa tindlela leti nga yimiki na leti nga cinciki ta vuswikoti. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo ka mimpimo yinharhu leyi tiyimeleke hi ku tirhisa xikombiso xin’we naswona ti le ndzeni ka 10%. e Ehenhla: Eka Ni(OH)2-NS, cyclohexanone leyingana ndzhawu yale hansi ya C yi adsorbed hiku tsana hi cyclohexanone, leswi endlaka leswaku kuva na mphikizano lowukulu eka OER. Ehansi: Eka NiV-LDH-NS, nhlayo yale henhla ya ndzhawu yale henhla ya cyclohexanone C ya voniwa hiku engeteleriwa ka adsorption ya cyclohexanone, leswi endlaka leswaku kuva na ku tshikileriwa ka OER. Data ya raw ya a–d yi nyikiwile eka fayili ya data ya raw.
Ku kambela ku antswisiwa ka adsorption ya cyclohexanone eka NiV-LDH-NS, hi tirhise electrochemical coupled quartz crystal microbalance (E-QCM) ku langutisisa ku cinca ka vukulu bya muxaka lowu adsorbed hi nkarhi wa xiviri. Mimbuyelo yi kombisile leswaku vuswikoti byo sungula bya adsorption bya cyclohexanone eka NiV-LDH-NS a byi ri byikulu hi minkarhi ya 1.6 ku tlula eka Ni(OH)2-NS eka xiyimo xa OCP, naswona ku hambana loku eka vuswikoti bya adsorption ku tlhele ku tlakuka loko vuswikoti byi tlakuka ku ya eka 1.5 VRHE (Xifaniso xo Engetela. 26). Swibalo swa DFT swa spin-polarized swi endliwile ku lavisisa mahanyelo ya adsorption ya cyclohexanone eka NiOOH na NiVOOH (Xifaniso 4c). Cyclohexanone yi adsorb eka Ni-center eka NiOOH hi adsorption energy (Eads) ya -0.57 eV, kasi cyclohexanone yinga adsorb eka Ni-center kumbe V-center eka NiVOOH, laha V-center yinyikaka Eads yale hansi swinene (-0.69 eV), leswi fambelanaka na adsorption yo tiya leyi voniweke ya cyclohexanone eka NiVOOH.
Ku ya emahlweni hi tiyisisa leswaku ku antswisiwa ka adsorption ya cyclohexanone ku nga tlakusa ku tumbuluxiwa ka AA na ku sivela OER, hi tirhise maqhinga ya vuswikoti byo nga yi emahlweni ku fuwisa cyclohexanone eka vuandlalo bya catalyst (eka Ni(OH)2-NS na NiV-LDH-NS), leswi hlohloteriweke hi swiviko swa khale. 51, 52 Hi ku kongoma, hi tirhise vuswikoti bya 1.8 VRHE eka COR, kutani hi yi cincela eka xiyimo xa OCP, ivi hi yi cinca yi tlhelela eka 1.8 VRHE. Eka xiyimo lexi, cyclohexanone yinga hlengeletana eka vuandlalo bya catalyst eka xiyimo xa OCP exikarhi ka ti electrolyses (vona xiyenge xa ​​Maendlelo ku kuma maendlelo ya vuxokoxoko). Mimbuyelo yi kombisile leswaku eka Ni(OH)2-NS na NiV-LDH-NS, ku tirhisa discontinuous potential electrolysis swi antswise matirhelo ya catalytic loko ku pimanisiwa na constant potential electrolysis (Xifaniso 4d). Lexi xiyekaka, Ni(OH)2-NS yi kombisile ku antswisiwa lokukulu swinene eka COR (AA FE: kusuka eka 51% kuya eka 82%) xikan’we naku tshikileriwa ka OER (O2 FE: kusuka eka 27% kuya eka 4%) kutlula NiV-LDH-NS, leswinga vangiwa hi mhaka ya leswaku nhlengeleto wa cyclohexanone wunga antswisiwa kuya eka mpimo lowukulu eka catalyst leyingana vuswikoti byo adsorption byo tsana (i.e., Ni(OH)2-NS) hi electrolysis ya vuswikoti byo tsekatseka.
Hiku angarhela, ku sivela ka OER eka NiV-LDH-NS swinga vangiwa hiku antswisiwa ka adsorption ya cyclohexanone (Xifaniso 4e). Eka Ni(OH)2-NS (Xifaniso 4e, ehenhla), ku adsorption loku tsaneke ka cyclohexanone swiendle leswaku kuva na cyclohexanone coverage yale hansi swinene xikan’we na OH* coverage yale henhla swinene eka catalyst surface. Hikokwalaho, tinxaka ta OH* leti tlulaka mpimo tita endla leswaku kuva na mphikizano lowukulu eka OER xikan’we naku hunguta FE ya AA. Kuhambana na sweswo, eka NiV-LDH-NS (Xifaniso 4e, ehansi), ku cinciwa ka V ku engetele vuswikoti bya adsorption bya cyclohexanone, hi ndlela yaleyo ku engetela surface C ya cyclohexanone naswona hi ndlela leyinene ku tirhisa muxaka wa OH* lowu adsorbed eka COR, ku hlohletela ku tumbuluxiwa ka AA na ku sivela OER.
Ku engetela eka ku lavisisa mbuyelo wa ku cinca ka V eka ku pfuxetiwa ka tinxaka ta Ni na cyclohexanone adsorption, hi tlhele hi lavisisa loko V yi cinca ndlela ya ku tumbuluxiwa ka AA kusuka eka COR. Tindlela to hlayanyana to hambana ta COR ti ringanyetiwile eka matsalwa, naswona hi xopaxophile ku koteka ka tona eka sisiteme ya hina ya ku angula (vona Xifaniso xo Engetela xa 27 na Xitsundzuxo xo Engetela xa 6 ku kuma vuxokoxoko byo tala)13,14,26. Xosungula, ku vikiwile leswaku goza rosungula ra ndlela ya COR ringa katsa oxidation yosungula ya cyclohexanone ku vumba key intermediate 2-hydroxycyclohexanone (2)13,14. Ku tiyisisa endlelo, hi tirhise 5,5-dimethyl-1-pyrrolidine N-oxide (DMPO) ku khoma switirhisiwa swa le xikarhi leswi tirhaka leswi adsorbed eka vuandlalo bya catalyst naswona hi dyondze hi EPR. Mimbuyelo ya EPR yi paluxe vukona bya ti radicals leti kongomisiweke eka C (R ) na ti radicals ta hydroxyl (OH ) eka ti catalysts leti hatimbirhi hi nkarhi wa endlelo ra COR, leswi kombisaka leswaku Cα − H dehydrogenation ya cyclohexanone yi vumba radical ya enolate ya le xikarhi (1), leyi endzhaku yi yaka emahlweni yi oxidized hi OH* ku vumba 2 (Fig. 5a na Supplementary Fig. 28). Hambi leswi ti intermediates leti fanaka ti tivekaka eka ti catalysts leti hatimbirhi, xiphemu xa ndzhawu ya xigingi xa R eka NiV-LDH-NS a xi ri ehenhla swinene ku tlula xa Ni(OH)2-NS, leswi nga ha vaka swi vangiwa hi vuswikoti byo adsorption lebyi antswisiweke bya cyclohexanone (Tafula ro Engetela 3 na Xitsundzuxo 7). Hi tlhele hi tirhisa 2 na 1,2-cyclohexanedione (3) tani hi switirhisiwa swo sungula swa electrolysis ku kambela loko V yi ta cinca goza ra oxidation leri landzelaka. Mbuyelo wa electrolysis wa switirhisiwa swa le xikarhi leswi nga kotekaka (2 na 3) eka Ni(OH)2-NS na NiV-LDH-NS wu kombisile ku hlawula ka swikumiwa leswi ringanisiwaka, leswi kombisaka leswaku ku angula ka COR eka Ni(OH)2-NS kumbe NiV-LDH-NS ku ye emahlweni hi tindlela leti fanaka (Xifaniso 5b). Ku tlula kwalaho, AA akuri xiendliwa lexikulu ntsena loko 2 yitirhisiwile tani hi reactant, leswi kombaka leswaku AA yikumeke hiku tirhisa endlelo ro kongoma ra oxidation hiku tirhisa cleavage ya Cα − Cβ bond ya 2 kutlula oxidation leyi landzelaka kuya eka 3 eka ti catalysts leti hatimbirhi, tani hileswi ngopfu ngopfu yi hundzuriweke GA loko 3 yitirhisiwile tani hi reactant yosungula (Swifaniso swo Engetela 29, 30).
Xikombiso xa EPR xa NiV-LDH-NS eka 0.5 M KOH + 0.4 M cyclohexanone. b Mimbuyelo ya nxopaxopo wa electrocatalytic wa 2-hydroxycyclohexanone (2) na 1,2-cyclohexanedione (3). Electrolysis yi endliwile eka 0.5 M KOH na 0.1 M 2 kumbe 3 eka 1.8 VRE kuringana awara yin’we. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo ka mimpimo yimbirhi leyi tiyimeleke hi ku tirhisa xihlohloteri xin’we. c Tindlela ta ku angula leti ringanyetiweke ta COR eka swihlohloteri swimbirhi. d Xifaniso xa xikimi xa ndlela ya COR eka Ni(OH)2-NS (exineneni) na d NiV-LDH-NS (exineneni). Miseve yo tshwuka yi kombisa magoza lawa ku cinciwa ka V ku ma hlohlotelaka eka phurosese ya COR. Data ya raw ya a na b yi nyikiwile eka fayili ya data ya raw.
Hi ku angarhela, hi kombisile leswaku Ni(OH)2-NS na NiV-LDH-NS swi catalyze COR hi ndlela leyi fanaka: cyclohexanone yi adsorbed eka catalyst surface, dehydrogenated naswona yi lahlekeriwa hi ti electrons ku vumba 1, leyi endzhaku yi oxidized hi OH* ku vumba 2, ku landzela multistep transformations ku humesa AA (Figure 5c). Hambiswiritano, loko cyclohexanone yitirhisiwa tani hi reactant, mphikizano wa OER wuvoniwe ntsena eka Ni(OH)2-NS, kasi nhlayo yale hansi ya oxygen yi hlengeletiwile loko 2 na 3 yitirhisiwile tani hi reactants. Xisweswo, ku hambana loku voniweke eka matirhelo ya catalytic kungava hikokwalaho ka ku cinca eka RDS energy barrier na cyclohexanone adsorption capacity leswi vangiwaka hiku cinca ka V kutlula ku cinca eka ndlela ya reaction. Hikokwalaho hi kambisisile RDS ya tindlela ta reaction eka ti catalysts leti hatimbirhi. Mimbuyelo leyi boxiweke laha henhla ya in situ X-ray acoustic spectroscopy yi kombisa leswaku ku cinciwa ka V ku cinca RDS eka COR reaction kusuka eka xiteji xa reconstruction kuya eka xiteji xa tikhemikhali, ku hlayisa xiphemu xa NiOOH na tinxaka ta Ni ta high-valent swinga onhakanga eka NiV-LDH-NS (Fig. 3f, Supplementary Fig. 24, na Note 4). Hi tlhele hi kambisisa maendlelo ya ku angula lama yimeriweke hi ku tsindziyela ka sweswi eka xiphemu xin’wana na xin’wana xa swifundzha swo hambana swa vuswikoti hi nkarhi wa ku pima ka CV (vona Xifaniso xo Engetela. 31 na Xitsundzuxo xa 8 ku kuma vuxokoxoko) naswona hi endle swikambelo swa ku cincana ka isotope ya H/D kinetic, leswi hi ku hlangana swi kombiseke leswaku RDS ya COR eka NiV-LDH-NS yi katsa ku tsemiwa ka xihlanganisi xa Cα − H eka xiteji xa tikhemikhali ku tlula ku hungutiwa xiteji (vona Xifaniso xo Engetela xa 32 na Xitsundzuxo xa 8 ku kuma vuxokoxoko byo tala).
Hi ku ya hi nxopaxopo lowu nga laha henhla, mbuyelo hinkwawo wa ku cinca ka V wu kombisiwile eka Xifaniso xa 5d. Ti catalysts ta Ni(OH)2-NS na NiV-LDH-NS ti hundza eka surface reconstruction eka ti anodic potentials tale henhla naswona ti catalyze COR hiku tirhisa ndlela yofana. Eka Ni(OH)2-NS (Xifaniso 5d, eximatsini), goza ro aka hi vuntshwa i RDS hi nkarhi wa phurosese ya COR; loko eka NiV-LDH-NS (Xifaniso 5d, exineneni), ku cinciwa ka V ku hatlisise swinene endlelo ro aka nakambe naswona ku hundzule RDS ku va Cα−H dehydrogenation ya cyclohexanone ku vumba 1. Ku engetela kwalaho, cyclohexanone adsorption yi humelerile eka ndzhawu ya V naswona yi antswisiwile eka NiV-LDH-NS, leswi hoxeke xandla eka ku tshikileriwa ka OER.
Hi ku tekela enhlokweni matirhelo ya kahle swinene ya electrocatalytic ya NiV-LDH-NS leyi nga na FE ya le henhla eka nhlayo yo anama ya vuswikoti, hi endlile MEA ku fikelela vuhumelerisi lebyi yaka emahlweni bya AA. MEA yi hlanganisiwile hiku tirhisa NiV-LDH-NS tani hi anode, PtRu/C ya mabindzu tani hi cathode53 na anion exchange membrane (muxaka: FAA-3-50) (Xifaniso 6a na Xifaniso xo Engetela. 33)54. Leswi voltage ya cell yi hungutekeke naswona FE ya AA ayi ringanisiwa na 0.5 M KOH eka dyondzo leyi nga laha henhla, nhlayo ya anolyte yi antswisiwile kuya eka 1 M KOH (Supplementary Fig. 25c). Ti curve ta LSV leti rhekhodiweke ti kombisiwile eka Supplementary Fig. 34, leswi kombisaka leswaku vukorhokeri bya COR bya NiV-LDH-NS byi le henhla swinene ku tlula bya Ni(OH)2-NS. Ku kombisa ku tlakuka ka NiV-LDH-NS, constant current electrolysis yi endliwile hi step current density kusuka eka 50 kuya eka 500 mA cm−2 naswona voltage ya cell leyi fambelanaka yi rhekhodiwile. Mbuyelo wu kombisile leswaku NiV-LDH-NS yi kombisile voltage ya cell ya 1.76 V eka current density ya 300 mA cm−2, leyi ayi ri kwalomu ka 16% ehansi kutlula ya Ni(OH)2-NS (2.09 V), leswi kombaka ku tirhisa eneji ya yona yale henhla eka vuhumelerisi bya AA (Fig. 6b).
Xifaniso xa xikimi xa betri yo khuluka. b Voltage ya sele handle ka iR compensation eka Ni(OH)2-NS na NiV-LDH-NS eka 1 M KOH na 0.4 M cyclohexanone eka ti current densities to hambana. c Mbuyelo wa AA na FE eka Ni(OH)2-NS na NiV-LDH-NS eka ti densities to hambana ta current. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo ka mimpimo yimbirhi leyi tiyimeleke hi ku tirhisa xihlohloteri xin’we. d Ku pimanisiwa ka matirhelo ya catalytic ya ntirho wa hina na tisisiteme tin’wana ta betri yo khuluka leti vikiweke14,17,19. Tipharamitha ta nhlamulo na swihlawulekisi swa nhlamulo swi xaxametiwile hi vuxokoxoko eka Tafula ro Engetela 2. e Voltage ya sele na FE ya AA eka NiV-LDH-NS eka 200 na 300 mA cm−2 eka xikambelo xa nkarhi wo leha, hi ku landzelelana. Data ya raw ya be yi nyikiwa tanihi fayili ya data ya raw.
Hi nkarhi walowo, tani hileswi swikombisiweke eka Fig. 6c, NiV-LDH-NS hi xisekelo yi hlayise FE ya kahle (83% kuya eka 61%) eka current density yale henhla (200 kuya eka 500 mA cm-2), hindlela yaleyo yi antswisa vuhumelerisi bya AA (1031 kuya eka 1900 μmol cm-2 h-1). Hi nkarhi wolowo, i 0.8% ntsena wa ti-anion ta adipic acid leti voniweke eka xiyenge xa ​​cathode endzhaku ka electrolysis, leswi kombisaka leswaku ku cinca ka cyclohexanone a ku nga ri ka nkoka eka xiyimo xa hina (Xifaniso xo Engetela. 35). Kuhambana na sweswo, hiku tlakuka loku fanaka ka current density, FE ya AA eka Ni(OH)2-NS yihunguteke kusuka eka 61% kuya eka 34%, leswinga endla leswaku switika ku antswisa vuhumelerisi bya AA (762 kuya eka 1050 μmol cm-2 h-1). Ngopfu ngopfu, matirhelo ya AA hambi kuri ku hunguteka nyana hikokwalaho ka mphikizano lowukulu kusuka eka OER, naswona xisweswo FE ya AA yi hungutekile swinene hiku tlakuka ka density ya sweswi (kusuka eka 200 kuya eka 250 mA cm−2, Supplementary Fig. 5). Hi ku ya hi vutivi bya hina, mbuyelo wa catalytic hi ku tirhisa MEA na ti NiV-LDH-NS catalysts wu tlula swinene matirhelo ya ti flow reactors leti vikiweke khale leti nga na ti catalysts leti simekiweke eka Ni (Tafula ro Engetela 2). Ku tlula kwalaho, tanihilaha swi kombisiweke hakona eka Fig. 6d, NiV-LDH-NS yi kombisile swipfuno leswikulu hi mayelana na current density, cell voltage, na FE ya AA loko yi pimanisiwa na Co-based catalyst leyi tirhaka kahle, i.e., graphene-supported Co3O4 (Co3O4/GDY)17. Ku engetela kwalaho, hi kambisisile ku tirhisiwa ka eneji ya vuhumelerisi bya AA naswona hi kombisile leswaku ku tirhisiwa ka AA a ku ri ehansi swinene, ntsena 2.4 W h gAA-1 eka current density ya 300 mA cm-2 na voltage ya sele ya 1.76 V (swibalo swa vuxokoxoko swi nyikiwile eka Supplementary Note 1). Loko ku pimanyisiwa na mbuyelo wa kahle wa 4.1 W h gAA-1 wa Co3O4/GDY lowu vikiweke khale, ku tirhisiwa ka eneji eka vuhumelerisi bya AA eka ntirho wa hina swihungutiwile hi 42% naswona vuhumelerisi byi engeteriwile hi 4 times (1536 vs. 319 μmol cm-2 h-1)17.
Ku tshamiseka ka NiV-LDH-NS catalyst eka vuhumelerisi bya nkarhi woleha bya AA eka MEA swikamberiwile eka ti densities ta sweswi ta 200 na 300 mA cm-2, hiku landzelelana (Xifaniso 6e). Leswi OH− yi dyiwaka hiku hatlisa eka ti current densities tale henhla, mpimo wa ku pfuxetiwa ka electrolyte eka 300 mA cm-2 wule henhla kutlula lowu nga eka 200 mA cm-2 (vona xiyengentsongo xa “Electrochemical measurements” ku kuma vuxokoxoko). Eka density ya sweswi ya 200 mA cm-2, average ya COR efficiency ayiri 93% eka 6 h yosungula, kutani yihunguteka nyana kuya eka 81% endzhaku ka 60 h, kasi cell voltage yi tlakuke nyana hi 7% (kusuka eka 1.62 V kuya eka 1.73 V), leswi kombaka kutshamiseka kahle. Hiku tlakuka ka current density kuya eka 300 mA cm−2, AA efficiency yitshame yinga cinci (yi hungutekile kusuka eka 85% kuya eka 72%), kambe cell voltage yi tlakuke swinene (kusuka eka 1.71 kuya eka 2.09 V, leswi fambelanaka na 22%) hi nkarhi wa 46-h test (Figure 6e). Hi ehleketa leswaku xivangelo lexikulu xa ku onhaka ka matirhelo i ku bola ka anion exchange membrane (AEM) hi cyclohexanone, leswi yisaka eka ku tlakuka ka ku lwisana ka tisele na voltage ya sele ya electrolyzer (Supplementary Fig. 36), leswi fambisanaka na ku khuluka nyana ka electrolyte kusuka eka anode kuya eka cathode, leswi endlaka leswaku kuva na kuhunguteka ka volume ya anolyte xikan’we na xilaveko xo yimisa ku endliwa ka electrolysis. Ku engetela kwalano, kuhunguteka ka FE ya AA swinga tlhela swivangiwa hiku khuluka ka ti catalysts, leswi tsakelaka ku pfuriwa ka Ni foam eka OER. Ku kombisa mbuyelo wa AEM leyi rhurhumeleke eka ku onhaka ka ku tshamiseka eka 300 mA cm−2, hi yi cincile hi AEM leyintshwa endzhaku ka 46 h ya electrolysis. Tani hilaha swi languteriweke hakona, vuswikoti bya catalytic byi vuyisiwile kahle, laha voltage ya cell yi hungutekeke swinene kuya eka ntikelo wosungula (kusuka eka 2.09 kuya eka 1.71 V) kutani yi tlakuka nyana eka 12 h leyi landzelaka ya electrolysis (kusuka eka 1.71 kuya eka 1.79 V, ku tlakuka ka 5%; Xifaniso 6e).
Hiku angarhela, hi kotile ku fikelela 60 h ya ku tshamiseka ka vuhumelerisi bya AA lebyi yaka emahlweni eka density ya sweswi ya 200 mA cm−2, leswi kombisaka leswaku FE na voltage ya cell ya AA swi hlayisiwile kahle. Hi tlhele hi ringeta ku va na current yale henhla ya 300 mA cm−2 naswona hi fikelela ku tshamiseka hinkwako ka 58 h, hi siva AEM hi leyintshwa endzhaku ka 46 h. Tidyondzo leti nga laha henhla ti kombisa ku tshamiseka ka catalyst naswona ti kombisa kahle xilaveko xa nhluvukiso wa nkarhi lowu taka wa ti-AEM ta matimba ya le henhla ku antswisa ku tshamiseka ka nkarhi wo leha ka MEA eka vuhumelerisi bya AA lebyi yaka emahlweni eka ti densities ta sweswi letinene eka tiindasitiri.
Hi ku ya hi matirhelo ya MEA ya hina, hi ringanyete endlelo ro hetiseka ra vuhumelerisi bya AA ku katsa na ku phameriwa ka substrate, electrolysis, neutralization, na tiyuniti to hambanyisa (Xifaniso xo Engetela. 37). Nxopaxopo wo sungula wa matirhelo wu endliwile ku kambela ku koteka ka ikhonomi ya sisiteme hi ku tirhisa modele wa vuhumelerisi bya alkaline electrolyte electrocatalytic carboxylate55. Eka xiyimo lexi, swiendleko swi katsa xiphemu xa mali, matirhelo, na switirhisiwa (Fig. 7a na Supplementary Fig. 38), naswona mimbuyelo yi huma eka vuhumelerisi bya AA na H2. Mimbuyelo ya TEA yi kombisa leswaku ehansi ka swiyimo swa hina swa ntirho (density ya sweswi 300 mA cm-2, voltage ya sele 1.76 V, FE 82%), ntsengo hinkwawo wa ntsengo na mimbuyelo i US$2429 na US$2564, hi ku landzelelana, leswi hundzuluxelaka eka mbuyelo wa ntsengo wa US$135 hi thani ya AA leyi humesiweke (vona Xitsundzuxo xo Engetela 9 ku kuma vuxokoxoko).
a Ntsengo hinkwawo wa phurosese ya AA electrochemical ehansi ka xiyimo xa xiyimo xa le hansi lexi nga na FE ya 82%, current density ya 300 mA cm−2, na cell voltage ya 1.76 V. Nxopaxopo wa sensitivity wa tihakelo tinharhu eka b FE na c current density. Eka nxopaxopo wa vutivi, i tipharamitha leti dyondziweke ntsena leti cinciweke naswona tipharamitha tin’wana ti hlayisiwile ti nga cinci hi ku ya hi modele wa TEA. d Vuyelo bya FE yo hambana na ku tsindziyela ka sweswi eka vuyelo bya AA electrosynthesis na vuyelo hi ku tirhisa Ni(OH)2-NS na NiV-LDH-NS, hi ku ehleketa leswaku voltage ya sele yi hlayisiwa yi nga cinci eka 1.76 V. Data yo nghenisa ya a–d yi nyikiwile eka fayili ya datha yo ka yi nga swekiwanga.
Hi ku ya hi xisekelo lexi, hi ye emahlweni hi lavisisa vuyelo bya FE na ku tsindziyela ka sweswi eka ku vuyeriwa ka AA electrosynthesis. Hi kumile leswaku ku vuyeriwa ku na vuxiyaxiya swinene eka FE ya AA, tanihileswi ku hunguteka ka FE ku yisaka eka ku tlakuka lokukulu ka ntsengo wa matirhelo, hi ndlela yoleyo ku engetela swinene ntsengo hinkwawo (Xifaniso 7b). Malunghana na density ya sweswi, density yale henhla ya current (>200 mA cm-2) yi pfuneta ku hunguta ntsengo wa capital xikan’we na ntsengo wo aka swimilani, ngopfu ngopfu hiku hunguta ndzhawu ya electrolytic cell, hindlela yaleyo swi hoxa xandla eka ku tlakuka ka mbuyelo (Figure 7c). Loko ku pimanisiwa na density ya sweswi, FE yina nkucetelo lowukulu swinene eka mbuyelo. Hi ku hlamusela nkucetelo wa FE na ku tsindziyela ka sweswi eka vuyelo, hi vona kahle nkoka wo fikelela FE ya le henhla (>60%) eka ku tsindziyela ka sweswi loku fambelanaka na tiindasitiri (>200 mA cm-2) ku tiyisisa ku vuyeriwa. Hikwalaho ka nhlayo yale henhla ya FE ya AA, sisiteme ya reaction na NiV-LDH-NS tani hi catalyst yitshama yiri kahle eka ndzhawu ya 100–500 mA cm−2 (pentagram dots; Figure 7d). Hambiswiritano, eka Ni(OH)2-NS, kuhungutiwa ka FE eka current density yale henhla (>200 mA cm−2) swiendle leswaku kuva na mbuyelo lowu nga tsakisiki (circles; Figure 7d), leswi kombisaka nkoka wa ti catalysts letingana FE yale henhla eka current density yale henhla.
Ku engetela eka nkoka wa swihlohloteri eka ku hunguta ntsengo wa xiphemu xa mali na matirhelo, nkambisiso wa hina wa TEA wu ringanyeta leswaku ku vuyeriwa ku nga antswisiwa ku ya emahlweni hi tindlela timbirhi. Xosungula i ku xavisa swin’we potassium sulfate (K2SO4) eka makete tani hi by-product ya neutralization unit, kambe na mbuyelo lowu nga vaka kona wa US$828/t AA-1 (Supplementary Note 9). Xavumbirhi i ku antswisa thekinoloji yo lulamisa, kukatsa na ku vuyiseriwa ka switirhisiwa kumbe ku tumbuluxiwa ka thekinoloji yo hambanyisa AA leyi nga durhiki swinene (swin’wana eka tiyuniti ta neutralization na ku hambanyisa). Endlelo ra acid-base neutralization leri tirhisiwaka sweswi ringa endla leswaku kuva na ntsengo wale henhla wa switirhisiwa (leswi endlaka xiphemu lexikulu eka 85.3%), laha 94% wa swona swivangiwa hi cyclohexanone na KOH ($2069/t AA-1; Figure 7a), kambe tani hileswi swinga boxiwaka laha henhla, endlelo ra ha vuyerisa hiku angarhela. Hi ringanyeta leswaku ku durha ka switirhisiwa ku nga ha hungutiwa ku ya emahlweni hi tindlela ta xiyimo xa le henhla swinene ta ku vuyisa KOH na cyclohexanone leyi nga endlangiki nchumu, ku fana na electrodialysis ku vuyiseriwa loku heleleke ka KOH14 (ku ringanyetiwa ka ntsengo wa US$1073/t AA-1 hi ku tirhisa electrodialysis; Xitsundzuxo xo Engetela xa 9).
Hi ku komisa, hi fikelerile vukorhokeri bya le henhla bya aluminium atom electrolysis eka current density ya le henhla hi ku nghenisa V eka Ni(OH)2 nanosheets. Ehansi ka nhlayo yo anama ya vuswikoti bya 1.5–1.9 VRHE na nhlayo yale henhla ya current ya 170 mA cm−2, AA FE eka NiV-LDH-NS yifikelele 83–88%, kasi OER yi tshikileriwile hindlela leyinene kuya eka 3%. Ku cinciwa ka V swi hlohletele kuhungutiwa ka Ni2+ kuya eka Ni3+x naswona swi ndlandlamuxe ku adsorption ya cyclohexanone. Data ya experimental na theoretical yi kombisa leswaku ku pfuxetiwa loku hlohloteriweke ku engetela density ya sweswi ya cyclohexanone oxidation naswona ku cinca RDS ya COR kusuka eka ku pfuxetiwa kuya eka dehydrogenation leyi katsaka Cα − H scission, kasi ku antswisiwa ka adsorption ya cyclohexanone ku tshikelela OER. Ku hluvukisiwa ka MEA ku fikelerile vuhumelerisi bya AA lebyi yaka emahlweni eka density ya current ya indasitiri ya 300 mA cm−2, rhekhodo ya AA efficiency ya 82%, na vuhumelerisi bya 1536 μmol cm−2 h−1. Xikambelo xa tiawara ta 50 xi kombisile leswaku NiV-LDH-NS yina ku tshamiseka lokunene tani hileswi yinga hlayisaka AA FE yale henhla eka MEA (> 80% kuringana 60 wa tiawara eka 200 mA cm−2; > 70% kuringana 58 wa tiawara eka 300 mA cm−2). Swifanele ku xiyiwa leswaku kuna xilaveko xo tumbuluxa ti AEM ta matimba swinene kuva ku fikeleriwa ntshamiseko wa nkarhi woleha eka ti densities ta current leti faneleke eka indasitiri. Ku engetela kwalaho, TEA yi kombisa swipfuno swa ikhonomi swa tindlela ta ku angula eka vuhumelerisi bya AA na nkoka wa swihlohloteri swa matirhelo ya le henhla na thekinoloji ya xiyimo xa le henhla yo hambanyisa ku ya emahlweni ku hunguta ku durha.