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Ku hungutiwa ka tikhemikhali ta gezi ta khaboni dayokisayidi ku ya eka formic acid i ndlela leyi tshembisaka yo antswisa ku tirhisiwa ka khaboni dayokisayidi naswona yi na matirhiselo lama nga kotekaka tanihi xitirhisiwa xo hlayisa hayidirojeni. Eka ntirho lowu, ku tumbuluxiwile xivumbeko xa nhlengeletano ya electrode ya zero-gap eka ku hlanganisiwa ko kongoma ka electrochemical ka formic acid kusuka eka carbon dioxide. Nhluvukiso wa nkoka wa thekinoloji i perforated cation exchange membrane, leyi, loko yitirhisiwa eka forward biased bipolar membrane configuration, yi pfumelelaka formic acid leyi vumbiweke eka membrane interface kuva yi rhurhisiwa hiku tirhisa anodic flow field hi nhlayo yale hansi ya 0.25 M. Handle ka swiphemu swo engetelela swa sandwich exikarhi ka anode na cathode mhaka leyi yi kongomisa eka ku tirhisa switirhisiwa swa betri leswinga kona na ti design leti tolovelekeke eka ti fuel cells na hydrogen electrolysis, leswi pfumelelaka ku cinca hiku hatlisa kuya eka scale-up naku xavisiwa. Eka sele ya 25 cm2, xivumbeko xa perforated cation exchange membrane xinyika >75% Faraday efficiency eka formic acid eka <2 V na 300 mA/cm2. Xa nkoka swinene, xikambelo xa 55-hour stability eka 200 mA/cm2 xikombe ku tiya ka Faraday efficiency xikan’we na cell voltage. Nxopaxopo wa techno-economic wu tirhisiwa ku kombisa tindlela to fikelela ku ringana ka ntsengo na tindlela ta sweswi ta vuhumelerisi bya formic acid.
Ku hungutiwa ka tikhemikhali ta gezi ta khaboni dayokisayidi ku ya eka formic acid hi ku tirhisa gezi leri pfuxetiwaka swi kombisiwile ku hunguta ku durha ka vuhumelerisi hi ku fika eka 75%1 loko ku pimanisiwa na tindlela ta ndhavuko leti simekiweke eka mafurha ya fossil. Hilaha swi kombisiweke hakona eka matsalwa2,3, formic acid yi na switirhisiwa swo hambana, ku suka eka ndlela leyi tirhaka kahle na ku hunguta ikhonomi yo hlayisa na ku fambisa hayidirojeni ku ya eka xitirhisiwa xo phamela indasitiri ya tikhemikhali4,5 kumbe indasitiri ya biomass6. Formic acid yi tlhele yi tiviwa tani hi xitirhisiwa xa swakudya eka ku hundzuriwa loku landzelaka ku va switirhisiwa swa le xikarhi swa mafurha ya jet leswi nga ta tshama nkarhi wo leha hi ku tirhisa vunjhiniyara bya metaboliki7,8. Hi ku hluvukisiwa ka ikhonomi ya formic acid1,9, mintirho yo hlaya ya ndzavisiso yi kongomisiwile eka ku antswisa ku hlawula ka catalyst10,11,12,13,14,15,16. Hambiswiritano, matshalatshala yotala ya ya emahlweni ya kongomisa eka ti H-cells letintsongo kumbe ti liquid flow cells leti tirhaka eka ti current densities tale hansi (<50 mA/cm2). Ku hunguta ku durha, ku fikelela ku xavisiwa na ku engetela ku nghena ka makete loku landzelaka, ku hungutiwa ka khaboni dayokisayidi ya tikhemikhali ta gezi (CO2R) ku fanele ku endliwa eka ti-current densities ta le henhla (≥200 mA/cm2) na ku tirha kahle ka Faraday (FE)17 loko ku ri karhi ku kurisiwa ku tirhisiwa ka switirhisiwa na ku tirhisa swiphemu swa betri ku suka eka tisele ta mafurha ta Thekinoloji na electrolysis ya mati swi pfumelela switirhisiwa swa CO2R ku tirhisa ikhonomi ya xikalo18. Ku engetela kwalano, ku engetela vukorhokeri bya vuhumelerisi naku papalata ku lulamisiwa loku engetelekeke ka le hansi, formic acid yifanele kutirhisiwa tani hi xiendliwa xohetelela kutlula ti formate salts19.
Eka tlhelo leri, matshalatshala ya sweswinyana ya endliwile ku tumbuluxa switirhisiwa swa CO2R formate/formic acid based gas diffusion electrode (GDE) leswi fambelanaka na tiindasitiri. Ndzavisiso lowu heleleke hi Fernandez-Caso et al.20 wu katsakanya swivumbeko hinkwaswo swa tisele ta electrochemical eka ku hunguta loku yaka emahlweni ka CO2 ku ya eka formic acid/formate. Hi ku angarhela, swivumbeko hinkwaswo leswi nga kona swi nga avanyisiwa hi swiyenge swinharhu leswikulu: 1. Ti-catholyte leti khulukaka19,21,22,23,24,25,26,27, 2. Xirhendzevutana xin’we (cation exchange membrane (CEM)28 kumbe anion exchange membrane (AEM)29 na 3. Swivumbeko swa sandwich15,30,31,32.Swiphemu swo tsemakanya leswi olovisiweke ya swivumbeko leswi swi kombisiwile eka Xifaniso xa 1a Eka xivumbeko xa ku khuluka ka catholyte, ku tumbuluxiwa kamara ra electrolyte exikarhi ka membrane na cathode ya GDE ku tumbuluxa tichannel ta ion eka leyara ya cathode ya catalyst33, hambi leswi xilaveko xa yona xo lawula ku hlawula ka formate ku kanetiwaka hi Chen et al cathode eka carbon substrate leyingana 1.27 mm hiku enta catholyte layer, kuya fika eka 90% FE 35 eka 500 mA/cm2 swifikeleriwile. Li et al., hiku tirhisa xivumbeko xin’we xa CEM, vafikelerile FE 29 ya 93.3% eka fractional current density ya 51.7 mA/cm2 Diaz-Sainz et al.28 va tirhisile filter press leyingana membrane yin’we ya CEM eka current density ya 45 mA/cm2 Hambiswiritano, maendlelo hinkwawo ya humelerisile formate kutlula xitirhisiwa lexi tsakeriwaka, formic acid swilaveko, eka swivumbeko swa CEM, tifomati to fana na KCOOH ti nga hatlisa ti hlengeletana eka nsimu ya GDE na ku khuluka, leswi vangaka swipimelo swa vutleketli naswona eku heteleleni ku tsandzeka ka sele.
Ku pimanisiwa ka swivumbeko swinharhu leswi dumeke swinene swa CO2R eka swivumbeko swa switirhisiwa swo hundzula formate/formic acid na architecture leyi ringanyetiweke eka ndzavisiso lowu. b Ku pimanisiwa ka mbuyelo hinkwawo wa current na formate/formic acid eka swivumbeko swa catholyte, swivumbeko swa sandwich, swivumbeko swa CEM yin’we eka matsalwa (leswi kombisiweke eka Tafula ro Engetela ra S1) na ntirho wa hina. Swikoweto leswi pfulekeke swikomba ku humelerisiwa ka formate solution, naswona swikoweto leswi tiyeke swikomba ku humelerisiwa ka formic acid. *Xivumbeko lexi kombisiweke hi ku tirhisa hayidirojeni eka anode. c Zero-gap MEA configuration hiku tirhisa composite bipolar membrane leyingana perforated cation exchange layer leyi tirhaka eka forward bias mode.
Ku sivela ku tumbuluxiwa ka formate, Proietto et al. 32 va tirhise xivumbeko xa splitless filter press configuration laha mati lawa yanga deionized ya khulukaka hi interlayer. Endlelo leri ringa fikelela >70% CE eka density ya sweswi ya 50–80 mA/cm2. Hilaha ku fanaka, Yang na van’wana. 14 yi ringanyete ku tirhisiwa ka interlayer ya electrolyte leyi tiyeke exikarhi ka CEM na AEM ku tlakusa ku vumbiwa ka formic acid. Yang et al.31,36 va fikelela 91.3% FE eka sele ya 5 cm2 eka 200 mA/cm2, leswi humesaka 6.35 wt% ya formic acid solution. Xia na van’wana. Hiku tirhisa xivumbeko lexi fanaka, 83% wa ku hundzuriwa ka carbon dioxide (CO2) kuya eka formic acid FE swifikeleriwile eka 200 mA/cm2, naswona ku tiya ka sisiteme swikamberiwile kuringana 100 wa tiawara 30 wa timinete. Hambi leswi mbuyelo wa xikalo lexintsongo wu tshembisaka, ku tlakuka ka ntsengo xikan’we naku rharhangana ka ti porous ion exchange resins swiendla leswaku switika ku ringanisa swivumbeko swa interlayer kuya eka tisisiteme letikulu (xikombiso, 1000 cm2).
Ku vona hi mahlo ya mianakanyo mbuyelo wa net wa tipulani to hambana, hi veke tafula ya vuhumelerisi bya formate/formic acid hi kWh eka tisisiteme hinkwato leti boxiweke eku sunguleni naswona hi ti plotile eka Xifaniso xa 1b. Swile rivaleni laha leswaku sisiteme yin’wana na yin’wana leyingana catholyte kumbe interlayer yita fika eka nhlohlorhi ya matirhelo ya yona eka ti current densities tale hansi naswona yi onhaka eka ti current densities tale henhla, laha ohmic limit yinga boha voltage ya cell. Ku tlula kwalaho, hambi leswi xivumbeko xa CEM lexi tirhisaka eneji xi nyikaka vuhumelerisi bya le henhla bya molar formic acid hi kWh, ku hlengeletiwa ka munyu swinga endla leswaku kuva na ku onhaka ka matirhelo hiku hatlisa eka ti current densities tale henhla.
Ku hunguta tindlela ta ku tsandzeka leti ku buriweke ha tona khale, hi tumbuluxile nhlengeletano ya electrode ya membrane (MEA) leyi nga na composite forward biased BPM leyi nga na perforated cation exchange membrane (PCEM). Xivumbeko xa yona xi kombisiwile eka Xifaniso xa 1c. Hydrogen (H2) yi nghenisiwa eka anode kuva yi humesa ti protons hiku tirhisa hydrogen oxidation reaction (HOR). Leyara ya PCEM yi nghenisiwa eka sisiteme ya BPM ku pfumelela ti formate ions leti endliweke eka cathode ku hundza eka AEM, ti hlangana na ti protons ku endla formic acid eka BPM interface na interstitial pores ya CEM, kutani ti huma hi GDE anode na flow field. . Hiku tirhisa xivumbeko lexi, hi fikelerile >75% FE ya formic acid eka <2 V na 300 mA/cm2 eka ndzhawu ya 25 cm2 ya ti cell. Xa nkoka swinene, dizayini yi tirhisa swiphemu leswi xavisiwaka na ti hardware architectures ta ti fuel cell na ti water electrolysis plants, leswi pfumelelaka nkarhi wo hatlisa wo ringanisa. Swivumbeko swa catholyte swina ti catholyte flow chambers leswinga vangaka ku nga ringani ka ntshikelelo exikarhi ka swiphemu swa gasi na mati, ngopfu ngopfu eka swivumbeko leswikulu swa ti cell. Eka swivumbeko swa sandwich leswingana ti porous layers ta fluid flow, matshalatshala ya nkoka ya laveka kuva ku antswisiwa porous intermediate layer kuva kuhungutiwa pressure drop xikan’we naku hlengeletiwa ka carbon dioxide endzeni ka intermediate layer. Leswi haswimbirhi swi nga endla leswaku ku kavanyeteka vuhlanganisi bya tisele. Switlhela switika ku humelerisa ti free-standing thin porous layers hi xikalo lexikulu. Kuhambana na sweswo, xivumbeko lexintshwa lexi ringanyetiweke i xivumbeko xa MEA xa zero-gap lexi nga riki na kamara ro khuluka kumbe leyara ya le xikarhi. Loko ku pimanisiwa na ti cells tin’wana ta electrochemical letinga kona, xivumbeko lexi ringanyetiweke xihlawulekile hikuva xi pfumelela ku hlanganisiwa hiku kongoma ka formic acid eka xivumbeko lexi nga ringanisiwaka, lexi tirhisaka eneji hi ndlela leyinene, ya zero-gap.
Ku tshikelela ku cinca ka hydrogen, matshalatshala lamakulu yo hunguta CO2 ya tirhise swivumbeko swa MEA na AEM membrane hiku hlanganisiwa na ti electrolytes ta molar concentration yale henhla (xikombiso, 1-10 M KOH) ku tumbuluxa swiyimo swa alkaline eka cathode (hilaha swi kombisiweke hakona eka Xifaniso xa 2a). Eka swivumbeko leswi, ti formate ions leti vumbiweke eka cathode ti hundza eka membrane tani hi tinxaka letinga na charge yo biha, kutani KCOOH yi vumbiwa naswona yi huma eka sisiteme hiku tirhisa anodic KOH stream. Hambi leswi formate FE na cell voltage ekusunguleni aswiri kahle tani hileswi swikombisiweke eka Figure 2b, ku kamberiwa ka stability swiendle leswaku kuva na kuhunguteka ka FE hi kwalomu ka 30% eka 10 h ntsena (Figure S1a–c). Swi fanele ku xiyiwa leswaku ku tirhisiwa ka 1 M KOH anolyte i swa nkoka swinene ku hunguta anodic overvoltage eka tisisiteme ta alkaline oxygen evolution reaction (OER)37 na ku fikelela ku fikelela ka ion endzeni ka mubedo wa cathode catalyst33. Loko nhlayo ya anolyte yihungutiwile kuya eka 0.1 M KOH, havumbirhi bya cell voltage na formic acid oxidation (ku lahlekeriwa hi formic acid) swa tlakuka (Figure S1d), leswi kombisaka zero-sum trade-off. Mpimo wa formate oxidation wu kamberiwile hiku tirhisa mass balance hinkwayo; ku kuma vuxokoxoko byo tala, vona xiyenge lexi nge “Maendlelo.” Ku tirha hiku tirhisa MEA na single CEM membrane configurations na swona swikamberiwile, naswona mbuyelo wu kombisiwile eka Xifaniso xa S1f,g. FE formate leyi hlengeletiweke kusuka eka cathode ayi >60% eka 200 mA/cm2 ekusunguleni ka xikambelo, kambe yi onhakile hiku hatlisa eka tiawara timbirhi hikokwalaho ka nhlengeleto wa munyu wa cathode lowu ku buriweke ha wona khale (Xifaniso xa S11).
Xikimi xa zero-gap MEA na CO2R eka cathode, hydrogen oxidation reaction (HOR) kumbe OER eka anode, na membrane yin’we ya AEM exikarhi. b FE na voltage ya sele ya xivumbeko lexi na 1 M KOH na OER leswi khulukaka eka anode. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo ka mimpimo yinharhu yo hambana. eka FE na voltage ya sele ya sisiteme na H2 na HOR eka anode. Mihlovo yohambana hambana yitirhisiwa ku hambanyisa vuhumelerisi bya formate na formic acid. d Xifaniso xa xikimi xa MEA lexi nga na BPM leyi rhurheriweke emahlweni exikarhi. FE na voltage ya betri ku hambana na nkarhi eka 200 mA/cm2 hiku tirhisa xivumbeko lexi. f Xifaniso xa xiphemu xo tsemakanya xa BPM MEA leyi nga na xihlawuhlawu endzhaku ka xikambelo xo koma.
Ku humelerisa formic acid, hydrogen yi phakeriwa eka Pt-on-carbon (Pt/C) catalyst eka anode. Tani hilaha swikombisiweke hakona eka Xifaniso xa 2d, forward-biased BPM leyi humesaka ti protons eka anode yi lavisisiwile khale ku fikelela vuhumelerisi bya formic acid. Yuniti ya BPM tuning yi tsandzekile endzhaku ka 40 wa timinete ta ntirho eka current ya 200 mA/cm2, leyi fambisanaka na voltage surge yo tlula 5 V (Fig. 2e). Endzhaku ko kamberiwa, delamination leyi nga erivaleni yi voniwile eka CEM/AEM interface. Handle ka formate, ti anions tofana na carbonate, bicarbonate na hydroxide tinga tlhela ti hundza eka AEM membrane naswona ti endla reaction na ti protons eka CEM/AEM interface kuva ti humesa gasi ya CO2 na mati ya mati, leswi yisaka eka BPM delamination (Fig. 2f) na , ekuheteleleni swiyisa eka ku tsandzeka ka ti cell.
Hi ku ya hi maendlelo ya matirhelo na ku tsandzeka ya xivumbeko lexi nga laha henhla, ku ringanyetiwa xivumbeko lexintshwa xa MEA tanihilaha swi kombisiweke hakona eka Xifaniso xa 1c naswona xi hlamuseriwile hi vuxokoxoko eka Xifaniso xa 3a38. Laha, leyara ya PCEM yinyika ndlela ya ku rhurha ka formic acid na ti anions kusuka eka CEM/AEM interface, hindlela yaleyo yi hunguta ku hlengeletiwa ka nchumu lowu. Hi nkarhi lowu fanaka, ndlela ya PCEM interstitial yi kongomisa formic acid eka diffusion medium na flow field, leswi hungutaka ku koteka ka formic acid oxidation. Mbuyelo wa polarization hiku tirhisa ti AEMs letingana vukulu bya 80, 40 na 25 mm wu kombisiwile eka Xifaniso xa 3b. Tani hilaha swi languteriweke hakona, hambi leswi voltage ya cell hinkwayo yi tlakukaka loko ku tlakuka ku enta ka AEM, ku tirhisa AEM yo tiya swi sivela ku hangalaka ka le ndzhaku ka formic acid, xisweswo swi engetela pH ya cathode na ku hunguta vuhumelerisi bya H2 (Fig. 3c–e).
a Xifaniso xa xivumbeko xa MEA lexi nga na AEM na CEM leyi pfulekeke na tindlela to hambana ta vutleketli bya formic acid. b Voltage ya sele eka ti current densities to hambana na vukulu byo hambana bya AEM. eka EE eka ti densities to hambana ta current letingana AEM thickness ya 80 μm (d) 40 μm, e) 25 μm. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo loku pimiweke ku suka eka swikombiso swinharhu swo hambana. f Mbuyelo wa ku tekelela wa nhlayo ya formic acid na nkoka wa pH eka CEM/AEM interface eka vukulu byo hambana bya AEM. f PC na pH eka cathode layer ya catalyst leyingana vukulu byohambana hambana bya AEM film. g Ku hangalasiwa ka swiphemu swimbirhi ka nhlayo ya formic acid na CEM/AEM interface na perforation.
Xifaniso xa S2 xikombisa ku hangalaka ka nhlayo ya formic acid na pH eka ku enta ka MEA hiku tirhisa Poisson-Nernst-Planck finite element modeling. A swi hlamarisi leswi nhlayo yale henhla ya formic acid, 0.23 mol/L, yi voniwaka eka CEM/AEM interface, tani hileswi formic acid yi vumbiwaka eka interface leyi. Nhlayo ya formic acid hiku tirhisa AEM yihunguteka hiku hatlisa loko ku enta ka AEM kukula, leswi kombaka ku lwisana lokukulu eka mass transfer xikan’we naku khuluka ka formic acid kutsongo hikokwalaho ka back diffusion. Swifaniso swa 3 f na g swikombisa mimpimo ya pH na formic acid eka mubedo wa cathode catalyst leswi vangiwaka hi ku hangalaka ka le ndzhaku na ku hangalasiwa ka swiphemu swimbirhi swa nhlayo ya formic acid, hiku landzelelana. Loko AEM membrane yi olova, nhlayo ya formic acid yiva e henhla ekusuhi na cathode, naswona pH ya cathode yiva acidic. Hikokwalaho, hambi leswi ti AEM membranes to tiya ti endlaka leswaku kuva na ku lahlekeriwa lokukulu ka ohmic, i swa nkoka swinene eka ku sivela ku hangalaka ka le ndzhaku ka formic acid kuya eka cathode xikan’we naku kurisa vutengi byale henhla bya sisiteme ya FE formic acid. Eku heteleleni, ku engetela ku enta ka AEM kuya eka 80 μm swiendle leswaku kuva na FE >75% eka formic acid eka <2 V na 300 mA/cm2 eka ndzhawu ya 25 cm2 ya ti cell.
Ku kambela ku tshamiseka ka architecture leyi leyi simekiweke eka PECM, current ya battery yi hlayisiwile eka 200 mA/cm2 kuringana 55 wa tiawara. Mimbuyelo hinkwayo yi kombisiwile eka Xifaniso xa 4, laha mbuyelo ku suka eka tiawara ta 3 to sungula wu kombisiwile eka Xifaniso xa S3. Loko ku tirhisiwa Pt/C anodic catalyst, voltage ya cell yi tlakuke swinene eka 30 min yosungula (Figure S3a). Eka nkarhi woleha, voltage ya cell yitshame yiri kwalomu ka nkarhi hinkwawo, leswi nyikaka mpimo wa ku onhaka wa 0.6 mV/h (Fig. 4a). Eku sunguleni ka xikambelo, PV ya formic acid leyi hlengeletiweke eka anode a yi ri 76.5% kasi PV ya hydrogen leyi hlengeletiweke eka cathode a yi ri 19.2%. Endzhaku ka awara yosungula ya ku kamberiwa, hydrogen FE yi yile ehansi kuya eka 13.8%, leswi kombaka ku antswisiwa ka ku hlawula ka formate. Hambiswiritano, oxidation rate ya formic acid eka sisiteme yi yile ehansi kuya eka 62.7% hi awara yin’we, naswona oxidation rate ya anodic formic acid yi tlakuke kusuka kwalomu ka zero ekusunguleni ka xikambelo kuya eka 17.0%. Endzhaku ka sweswo, FE ya H2, CO, formic acid xikan’we na mpimo wa anodic oxidation ya formic acid switshame swirikarhi switshamisekile hinkarhi wa ku ringeta. Ku tlakuka ka formic acid oxidation eka awara yosungula swinga vangiwa hiku hlengeletiwa ka formic acid eka PCEM/AEM interface. Loko nhlayo ya formic acid yikula, ayi humi ntsena hiku pfuleka ka membrane, kambe yitlhela yi hangalaka hiku tirhisa FEM hi yoxe naswona yi nghena eka Pt/C anode layer. Leswi formic acid yinga mati eka 60°C, ku hlengeletiwa ka yona swinga vanga swiphiqo swa mass transfer naswona swi endla leswaku kuva na oxidation yotsakela kutlula hydrogen.
a Voltage ya sele ku pimanisiwa na nkarhi (200 mA/cm2, 60 °C). Inset yi kombisa xifaniso xa optical microscope xa xiphemu xo tsemakanya xa MEA lexi nga na EM leyi pfulekeke. Bar ya xikalo: 300 μm. b Ku basa ka PE na formic acid tani hi ntirho wa nkarhi eka 200 mA/cm2 hiku tirhisa Pt/C anode.
Mofoloji ya swikombiso ekusunguleni ka ku kamberiwa (BOT) hi nkarhi wa ku lulamisela na le makumu ka ku kamberiwa (EOT) endzhaku ka 55 h ya ku kamberiwa ka ku tshamiseka yi hlawuriwile hi ku tirhisa nano-X-ray computed tomography (nano-CT), tanihilaha swi kombisiweke hakona eka Xifaniso 5 a. Xikombiso xa EOT xina vukulu bya catalyst particle size leyingana diameter ya 1207 nm loko ku pimanyisiwa na 930 nm eka BOT. Swifaniso swa high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) na mbuyelo wa energy-dispersive X-ray spectroscopy (EDS) swi kombisiwile eka Xifaniso xa 5b. Loko BOT catalyst layer yina vunyingi bya ti catalyst particles letintsongo xikan’we na ti agglomerates tin’wana letikulu, eka xiteji xa EOT catalyst layer yinga avanyisiwa hi tindzhawu timbirhi tohambana: yin’wana yina ti solid particles letikulu swinene kasi yin’wana yina tindzhawu letingana ti porous swinene. Nhlayo ya swiphemu leswintsongo. Xifaniso xa EDS xikombisa leswaku swiphemu leswikulu leswi tiyeke swifuwile hi Bi, swinga endleka kuri metallic Bi, naswona tindzhawu letinga porous ti fuwile hi oxygen. Loko sele yi tirhisiwa eka 200 mA/cm2, vuswikoti byo biha bya cathode byi ta vanga ku hunguteka ka Bi2O3, tani hileswi swi kombisiweke hi mbuyelo wa in situ X-ray absorption spectroscopy lowu boxiweke laha hansi. Mbuyelo wa HAADF-STEM na EDS mapping wukombisa leswaku Bi2O3 yi hundza eka endlelo ro hunguta, leswi endlaka leswaku yi lahlekeriwa hi oxygen naswona yi agglomerate eka swiphemu leswikulu swa nsimbi. Tipheteni ta X-ray diffraction ta ti cathode ta BOT na EOT ti tiyisisa nhlamuselo ya data ya EDS (Fig. 5c): i Crystalline Bi2O3 ntsena leyi kumiweke eka BOT cathode, naswona crystalline bimetal yi kumiwile eka EOT cathode. Ku twisisa mbuyelo wa cathode potential eka xiyimo xa oxidation xa Bi2O3 cathode catalyst, mahiselo ya cinciwile kusuka eka open circuit potential (+0.3 V vs RHE) kuya eka -1.5 V (vs RHE). Ku xiyiwile leswaku xiphemu xa Bi2O3 xisungula kuhungutiwa eka -0.85 V loko ku pimanyisiwa na RHE, naswona kuhunguteka ka matimba ya layini yo basa eka ndzhawu yale makumu ya spectrum swikomba leswaku metallic Bi yihungutiwile kuya eka 90% wa RHE eka -1.1. V ku lwisana na RHE (Xifaniso 5d). Kunga khathariseki endlelo, ku hlawula hinkwako ka formate eka cathode hi xiviri aswi cinci, tani hileswi swinga ehleketeleriwa kusuka eka H2 na CO FE na ku tumbuluxiwa ka formic acid, hambi leswi kungana ku cinca lokukulu eka cathode morphology, catalyst oxidation state, na microcrystalline structure.
a Xivumbeko xa swiphemu swinharhu xa leyara ya xihlohloteri na ku hangalasiwa ka swiphemuphemu swa xihlohloteri leswi kumiweke hi ku tirhisa nano-X-ray CT. Bar ya xikalo: 10 μm. b Ehenhla 2: Swifaniso swa HAADF-STEM swa swiphemu swa cathode swa swihlohloteri swa BOT na EOT. Bar ya xikalo: 1 μm. Ehansi 2: Swifaniso leswi kurisiweke swa HADF-STEM na EDX swa leyara ya cathode ya catalyst ya EOT. Bar ya xikalo: 100 nm. c Tipheteni ta X-ray diffraction ta swikombiso swa BOT na EOT cathode. d In situ X-ray absorption spectra ya Bi2O3 electrode eka 0.1 M KOH tani hi ntirho wa vuswikoti (0.8 V kuya eka -1.5 V vs. RHE).
Ku kumisisa kahle leswaku hi swihi swivandlanene leswi nga kona swo antswisa ku tirhisiwa ka eneji hi ku sivela ku oxidation ka formic acid, ku tirhisiwile electrode ya reference ya H2 ku kuma ku hoxa xandla ka ku lahlekeriwa hi voltage39. Eka current densities yale hansi ka 500 mA/cm2, cathode potential yitshama ehansi ka -1.25 V. anodic potential yi avanyisiwile hi swiphemu swimbirhi leswikulu: exchange current density HOR na theoretical overvoltage HOR 40 leyi vhumbhiweke hi Bulter-Volmer equation leyi pimiweke khale, naswona xiphemu lexi saleke xivangiwa hi oxidation formic acid. Hikwalaho ka kinetics ya reaction leyi nonokaka swinene loko ku pimanyisiwa na HOR41, mpimo wutsongo wa formic acid oxidation reaction eka anode wunga endla leswaku kuva na ku tlakuka lokukulu eka anodic potential. Mbuyelo wukombisa leswaku ku sivela hiku hetiseka ka formic acid anodic oxidation swinga herisa kwalomu ka 500 mV overvoltage.
Ku kambela xiringanyeto lexi, mpimo wa ku khuluka ka mati ya deionized (DI) eka ndzhawu yo nghena ya anode wu cinciwile ku hunguta nhlayo ya effluent formic acid. Swifaniso swa 6b na c swikombisa FE, nhlayo ya formic acid, na voltage ya sele tani hi ntirho wa DI flux eka anode eka 200 mA/cm2. Loko nhlayo ya mati lawa yanga deionized yi tlakuka kusuka eka 3.3 mL/min kuya eka 25 mL/min, nhlayo ya formic acid eka anode yihunguteke kusuka eka 0.27 mol/L kuya eka 0.08 mol/L. Loko hi pimanisa, hi ku tirhisa xivumbeko xa sandwich lexi ringanyetiweke hi Xia et al. 30 nhlayo ya formic acid ya 1.8 mol/L yikumeke eka 200 mA/cm2. Kuhunguta nhlayo swiantswisa FE hinkwayo ya formic acid naswona swihunguta FE ya H2 loko cathode pH yiva na alkaline swinene hikokwalaho ka kuhunguteka ka back diffusion ya formic acid. Kuhunguteka ka nhlayo ya formic acid eka maximum DI flow switlhele swiherisa kahle formic acid oxidation, leswinga endla leswaku kuva na total cell voltage yale hansi nyana ka 1.7 V eka 200 mA/cm2. Ku hisa ka betri na kona ku khumba matirhelo hinkwawo, naswona mbuyelo wu kombisiwile eka Xifaniso xa S10. Hambiswiritano, ti architectures leti simekiweke eka PCEM tinga antswisa swinene ku tirhisiwa kahle ka eneji eka ku sivela formic acid oxidation, kungava hiku tirhisa ti anodic catalysts letingana ku antswisiwa ka hydrogen selectivity kuya eka formic acid kumbe hiku tirhisa switirhisiwa.
a Ku hahluka ka voltage ya sele hi ku tirhisa electrode ya cell reference H2 leyi tirhaka eka 60 °C, Pt/C anode na 80 μm AEM. b FE na formic acid concentrations leyi hlengeletiweke eka 200 mA/cm2 hiku tirhisa ti flow rates to hambana ta mati lawa yanga anodic deionized. c Loko anode yi hlengeleta formic acid hi ti concentrations to hambana, voltage ya cell i 200 mA/cm2. Tibara ta swihoxo ti yimela ku hambuka ka ntolovelo ka mimpimo yinharhu yo hambana. d Ntsengo wa le hansi wo xavisa lowu hambanisiweke hi matirhelo eka mimpimo yo hambana ya ku khuluka ka mati lama nga riki na ayoni hi ku tirhisa minxavo ya gezi ya le xikarhi ya tiindasitiri ya rixaka ya US$0.068/kWh na US$4.5/kg ya hayidirojeni. (*: Xiyimo xa le hansi xa oxidation xa formic acid eka anode xi tekiwa tani hi 10 M FA, ntsengo wa gezi wa indasitiri wa xikarhi wa tiko i $0.068/kWh, naswona hydrogen i $4.5/kg. **: Xiyimo xa le hansi xa oxidation xi tekiwa tani hi formic acid. Nhlayo ya FA eka anode i 1.3 M anode, nxavo wa gezi wa nkarhi lowu taka i $0.03/kWh, na layini leyi nga na mathonsi yi yimela nxavo wa makete wa 85 wt% FA.
Nxopaxopo wa thekinoloji-ikhonomi (TEA) wu endliwile ku kuma ntsengo wa le hansi wo xavisa wa tinhlengeletano ta mafurha ehansi ka swiyimo swo hambana swa matirhelo, tanihilaha swi kombisiweke hakona eka Xifaniso xa 5d. Maendlelo na datha ya le ndzhaku ya TEA swi nga kumeka eka SI. Loko nhlayo ya LC eka anode exhaust yiri e henhla, hambi leswi kungana voltage yale henhla ya cell, ntsengo hinkwawo wa nhlengeletano ya mafurha wuhunguteka hikokwalaho ka kuhunguteka ka ntsengo wo hambanyisa. Loko anodic oxidation ya formic acid yinga hungutiwa hiku tirhisa catalyst development kumbe electrode technology, kuhlanganisiwa ka cell voltage yale hansi (1.66 V) xikan’we na FA concentration yale henhla eka effluent (10 M) swinga hunguta ntsengo wa vuhumelerisi bya electrochemical FA kuya eka 0.74 US dollars/kg (leswi seketeriweke eka gezi). nxavo) $0.068/kWh na $4.5/kg ya hayidirojeni42. Ku tlula kwalaho, loko swi hlanganisiwa na ntsengo lowu languteriweke wa nkarhi lowu taka wa gezi leri pfuxetiwaka wa $0.03/kWh na hayidirojeni ya $2.3/kg, xikongomelo xa mati ya thyaka ya FA xi hungutiwile ku ya eka 1.3 wa timiliyoni, leswi endlaka leswaku ntsengo wo hetelela lowu languteriweke wa vuhumelerisi i US$0.66/kg43. Leswi swiringanisiwa na minxavo ya sweswi ya makete. Xisweswo, matshalatshala ya nkarhi lowu taka lawa ya kongomisiweke eka switirhisiwa swa ti electrode na swivumbeko yanga ya emahlweni ya hunguta anodization loko kurikarhi ku pfumelela ntirho eka ti voltage tale hansi ta ti cell kuva ku humelerisa nhlayo yale henhla ya LC.
Hi ku komisa, hi dyondze swivumbeko swo hlayanyana swa MEA swa zero-gap swa ku hunguta CO2 ku ya eka formic acid naswona hi ringanyete xivumbeko lexi nga na composite forward-biased bipolar membrane ku katsa na perforated cation exchange membrane (PECM) ku olovisa membrane mass transfer interface ya formic acid leyi humelelaka. . Xivumbeko lexi xi humesa >96% formic acid eka nhlayo yofika eka 0.25 M (eka anode DI flow rate ya 3.3 mL/min). Eka ti DI flow rates tale henhla (25 mL/min), xivumbeko lexi xinyikile current density ya >80% FE ya 200 mA/cm2 eka 1.7 V hiku tirhisa ndzhawu ya cell ya 25 cm2. Eka ti anodic DI rates to ringanela (10 mL/min), xivumbeko xa PECM xi hlayise voltage leyi tiyeke na ti levele tale henhla ta formic acid FE kuringana 55 h ya ku kamberiwa eka 200 mA/cm2. Ku tshamiseka ka le henhla na ku hlawula loku fikeleriwa hi ti catalysts leti xavisiwaka na switirhisiwa swa polymeric membrane swinga antswisiwa kuya emahlweni hiku swihlanganisa na ti electrocatalysts leti antswisiweke. Ntirho lowu landzelaka wu ta kongomisa eka ku lulamisa swiyimo swa ntirho, ku hlawula ka anode catalyst, na xivumbeko xa MEA ku hunguta oxidation ya formic acid, leswi endlaka leswaku ku va na effluent leyi hlanganisiweke swinene eka ti voltage ta tisele ta le hansi. Ndlela yo olova yo tirhisa khaboni-dayokisayidi eka formic acid leyi nyikeriweke laha yi herisa xilaveko xa makamara ya anolyte na catholyte, swiphemu swa sandwich, na switirhisiwa swo hlawuleka, xisweswo yi engetela ku tirhisiwa kahle ka eneji ya tisele na ku hunguta ku rharhangana ka sisiteme, leswi endlaka leswaku swi olova ku kurisa. Xivumbeko lexi ringanyetiweke xi nyika pulatifomo ya nhluvukiso wa nkarhi lowu taka wa tipulani to hundzula CO2 leti nga na vukorhokeri bya xithekiniki na ikhonomi.
Handle ka loko swi boxiwile hi ndlela yin’wana, switirhisiwa hinkwaswo swa giredi ya tikhemikhali na swintshuxo switirhisiwile tani hileswi swi amukeriweke. Bismuth oxide catalyst (Bi2O3, 80 nm) yi xaviwile kusuka eka US Research Nanomaterials, Inc. Polymer powder (AP1-CNN8-00-X) yi nyikiwile hi IONOMR. Omnisolv® brand N-propanol (nPA) na mati yo basa swinene (18.2 Ω, Milli–Q® Advantage A10 water purification system) swi xaviwile kusuka eka Millipore Sigma. Methanol na acetone leswi tiyisisiweke hi ACS swi xaviwile kusuka eka VWR Chemicals BDH® na Fisher Chemical, hiku landzelelana. Powder ya polymer yi hlanganisiwe na nkatsakanyo wa acetone na methanol hi ratio ya 1:1 hi ntiko kuva ku kumiwa polymer dispersion leyingana nhlayo ya 6.5 wt.%. Lulamisa inki ya catalytic hiku hlanganisa 20g Bi2O3, mati ya ultrapure, nPA na ionomer dispersion eka xibya xa 30ml. Xivumbeko lexi axiri na 30 wt.% catalyst, mass ratio ya ionomer kuya eka catalyst ya 0.02 na mass ratio ya alcohol kuya eka mati ya 2:3 (40 wt.% nPA). Loko kungase hlanganisiwa, 70g ya Glen Mills 5mm zirconia grinding material yi cheriwile eka nkatsakanyo. Tisampulu ti vekiwile eka FisherbrandTM digital bottle roller eka 80 rpm kuringana 26 wa tiawara. Pfumelela inki yi tshama kuringana 20 wa timinete loko unga se yi chela. Inki ya Bi2O3 yi cheriwile eka Qualtech automatic applicator (QPI-AFA6800) hiku tirhisa 1/2′′ x 16′′ laboratory wirewound refill (RD Specialties – 60 mil diameter) eka 22°C. 5 mL ya inki ya catalytic yi cheriwile eka 7.5 x 8 inch Sigraacet 39 BB carbon gas diffusion carrier (vuhlayiselo bya fuel cell) hiku vekiwa ka rod hi rivilo ra xikarhi leri nga cinciki ra 55 mm/sec. Tlhuvulela ti electrodes leti leti pfanganisiweke eka oven kutani u ti omisa eka 80 °C. Endlelo ro peta nhonga na swifaniso swa ku peta ka GDE swi kombisiwile eka Swifaniso swa S4a na b. Xitirhisiwa xa X-ray fluorescence (XRF) (Fischerscope® XDV-SDD, Fischer-Technolgy Inc. USA) xi tiyisisile leswaku ku layicha ka GDE leyi pfanganisiweke akuri 3.0 mg Bi2O3/cm2.
Eka swivumbeko swa membrane leswi hlanganisiweke leswingana anion exchange membrane (AEM) na CEM leyi pfulekeke. Nafion NC700 (Chemours, USA) leyingana vukulu bya vito bya 15 μm yitirhisiwile tani hi CEM layer. Catalyst ya anodic yi fafazeriwile hiku kongoma eka FEM hi ionomer kuya eka carbon ratio ya 0.83 na ndzhawu yo funengeta ya 25 cm2. Platinum leyi seketeriweke leyingana ndzhawu leyikulu yale henhla (50 wt.% Pt/C, TEC 10E50E, TANAKA precious metal) leyingana ndzhwalo wa 0.25 mg Pt/cm2 yitirhisiwile tani hi anode catalyst. Nafion D2020 (Ion Power, USA) yitirhisiwile tani hi ionomer ya anode layer ya catalyst. CEM perforation yi endliwa hiku tsema milayeni leyi fambelanaka eka film ya CEM eka 3mm intervals. Vuxokoxoko bya endlelo ro pfuleka byi kombisiwile eka Swifaniso swa S12b na c. Hiku tirhisa X-ray computed tomography, switiyisisiwile leswaku xivandla xa perforation akuri 32.6 μm, tani hileswi swikombisiweke eka Figure S12d na e. Hi nkarhi wa nhlengeletano ya ti cell, catalyst-coated perforated CEM membrane yi vekiwile eka 25 cm2 Toray paper (5 wt% PTFE treated, Fuel Cell Store, USA). AEM membrane (PiperION, Versogen, USA) leyingana vukulu bya 25, 40 kumbe 80 μm yi vekiwile ehenhla ka CEM kutani yi vekiwa eka GDE cathode. Membrane ya AEM yi tsemiwile yiva swiphemu swa 7.5 × 7.5 cm kuva yi funengeta nsimu hinkwayo yo khuluka naswona yi cheriwile vusiku hinkwabyo eka 1 M potassium hydroxide solution loko yinga se hlanganisiwa. Havumbirhi bya anode na cathode switirhisa ti PTFE spacers letinga tiya swinene kuva ti fikelela ntshikelelo wa kahle wa GDE wa 18%. Vuxokoxoko bya endlelo ro hlengeleta betri byi kombisiwile eka Xifaniso xa S12a.
Hi nkarhi wa ku kamberiwa, sele leyi hlanganisiweke yi hlayisiwile eka 60 °C (30, 60, na 80 °C eka tidyondzo ta ku titshega hi mahiselo) na 0.8 L/min ya gasi ya hydrogen leyi phakeriwaka eka anode na 2 L/min ya carbon dioxide leyi phakeriwaka eka cathode. Havumbirhi bya swinambyana swa moya swa anodic na cathodic switsakama eka 100% relative humidity na 259 kPa absolute cathodic pressure. Hi nkarhi wa ntirho, xirhendzevutani xa gasi ya cathode xi hlanganisiwile na 1 M KOH solution hi mpimo wa 2 mL/min ku tlakusa ku tirhisiwa ka mubedo wa cathode catalyst na ionic conduction. Hlanganisa nambu wa gasi ya anode na mati lawa yanga deionized hi rivilo ra 10 ml/min ku susa formic acid eka anode. Vuxokoxoko bya swingheniso na swihumesi swa xitirhisiwa swi kombisiwile eka Xifaniso xa S5. Gasi ya cathode exhaust yina CO2 naswona yi humesa CO na H2. Mpfula ya mati yi susiwa hiku tirhisa condenser (low temperature heat exchanger eka 2°C). Gasi leyi saleke yi ta hlengeletiwa ku endlela nxopaxopo wa nkarhi wa gasi. Ku khuluka ka anode kuta tlhela ku hundza eka condenser ku hambanyisa mati na gasi. Mati ya thyaka yata hlengeletiwa eka ti vials leti tengeke naswona ya kamberiwa hiku tirhisa liquid chronometry ku pima nhlayo ya formic acid leyi humelerisiwaka. Swikambelo swa tikhemikhali ta gezi swi endliwile hi ku tirhisa Garmy potentiostat (nomboro ya xikombo 30K, Gamry, USA). Loko kungase pimiwa polarization curve, cell yi endliwile 4 times eka range kusuka eka 0 kuya eka 250 mA/cm2 hiku tirhisa linear voltammetry leyingana scan rate ya 2.5 mA/cm2. Ti polarization curves tikumeke eka galvanostatic mode laha cell yi khomiweke eka current density yokarhi kuringana 4 wa timinete loko kungase tekiwa xikombiso xa gasi ya cathode na mati ya anolyte.
Hi tirhisa electrode ya hydrogen reference eka MEA ku hambanyisa ti cathode na ti anodic potentials. Xivumbeko xa electrode ya reference xi kombisiwile eka Xifaniso xa S6a. Membrane ya Nafion (Nafion 211, IonPower, USA) yitirhisiwile tani hi buloho ra ionic ku hlanganisa membrane ya MEA na electrode ya reference. Makumu yan’we ya Nafion strip ya hlanganisiwile na 1 cm2 gas diffusion electrode (GDE) leyi layichiweke hi 0.25 mg Pt/cm2 (50 wt% Pt/C, TEC10E50E, TANAKA Precious Metals) leyi pfanganisiweke eka phepha ra khaboni ra 29BC (Fuel Cell Store, USA). ). Hardware yo hlawuleka ya polyetheretherketone (PEEK) yi tirhisiwa ku pfalela gasi na ku tiyisisa ku hlangana lokunene exikarhi ka swiphemu swa GDE na Nafion, na ku hlanganisa electrode ya ndzavisiso eka hardware ya sele ya mafurha. Makumu man’wana ya Nafion strip ya hlanganisiwa na tlhelo leri humelaka ehandle ra betri ya CEM. Xifaniso xa S6b xi kombisa xiphemu xo tsemakanya xa electrode ya reference leyi hlanganisiweke na MEA.
Endzhaku kaloko gasi leyi humesiwaka yi hundze eka condenser na gas-liquid separator, swikombiso swa gasi swi tekiwa eka cathode. Gasi leyi hlengeletiweke yi kamberiwile kwalomu ka kanharhu hiku tirhisa 4900 Micro GC (10 μm molecular sieve, Agilent). Tisampulu ti hlengeletiwile eka inert multi-layer aluminium foil gas sample bags SupelTM (Sigma-Aldrich) kuringana nkarhi lowu vekiweke (30 seconds) naswona ti nghenisiwile hi voko eka microgas chromatograph eka tiawara timbirhi endzhaku ka ku hlengeletiwa. Mahiselo ya injection ya vekiwile eka 110°C. Carbon monoxide (CO) na hydrogen (H2) swi hambanisiwile eka kholomo leyi hisiweke (105 °C) leyi tshikileleriweke (28 psi) ya 10 m MS5A hiku tirhisa argon (Matheson Gas-Matheson Purity) tani hi gasi yo rhwala. Swihlanganisi leswi swi voniwa hiku tirhisa Thermal Conductivity Detector (TCD) leyi akiweke endzeni. Ti chromatograms ta GC na ti curve ta CO na H2 calibration swi kombisiwile eka Xifaniso xa S7. Tisampulu ta liquid formic acid ti hlengeletiwile kusuka eka anode kuringana nkarhi lowu vekiweke (120 seconds) naswona ti sefiwile hiku tirhisa 0.22 μm PTFE syringe filter eka 2 mL vials. Switirhisiwa swa mati eka ti vials swikamberiwile hiku tirhisa Agilent 1260 Infinity II bioinert high-performance liquid chromatography (HPLC) system, laha 20 μl ya xikombiso yi cheriweke hiku tirhisa autosampler (G5668A) na mobile phase ya 4 mM sulfuric acid (H2SO4). ) eka mpimo wa ku khuluka wa 0.6 ml/min (pompo ya quaternary G5654A). Swihumelerisiwa swi hambanisiwile eka kholomo leyi hisiweke (35°C, column oven G7116A) Aminex HPX-87H 300 × 7.8 mm (Bio-Rad) leyi rhangelaka hi Micro-Guard Cation H guard column. Formic acid yikumiwile hiku tirhisa diode array detector (DAD). eka wavelength ya 210 nm na bandwidth ya 4 nm. HPL chromatogram na formic acid standard calibration curve swi kombisiwile eka Xifaniso xa S7.
Swikumiwa swa gasi (CO na H2) FE swi hlayeriwa hiku tirhisa xiringaniso lexi landzelaka, naswona ti moles hinkwato ta gasi ti hlayeriwa hiku tirhisa xiringaniso xa gasi lexinene:
Exikarhi ka swona: \({n}_{i}\): nhlayo ya tielektroni eka ku cinca ka tikhemikhali ta gezi. \(F\): Xihlawulekisi xa Faraday. \({C}_{i}\): Nhlayo ya swikumiwa swa mati ya HPLC. \(V\): vholumo ya xikombiso xa mati lexi hlengeletiweke eka nkarhi lowu vekiweke t. \(j\): ku tsindziyela ka sweswi. \(A\): Ndhawu ya geometri ya electrode (25 cm2). \(t\): nkarhi wa ku tekela swikombiso. \(P\): ntshikilelo lowu heleleke. \({x}_{i}\): Tiphesente ta mole ta gasi leti kumiweke hi GC. \(R\): xiyimo xa gasi. \(T\): mahiselo.
Nhlayo ya ti anodic cations yi pimiwile hiku tirhisa inductively coupled plasma atomic emission spectroscopy (ICP-OES). Ti cations letinga leach kumbe ku hangalaka eka anode ti katsa Ti, Pt, Bi na K. Handle ka K, ti cations tin’wana hinkwato atiri ehansi ka mpimo wa ku kumiwa. Vumba ti ions eka solution ku siya anode kuva yi fambisana na ti protons kumbe ti cations tin’wana. Hikokwalaho, ku basa ka formic acid kunga hlayiwa tani hi
Vuhumelerisi bya Formate/FA byi yimela nhlayo ya FA leyi humelerisiwaka hi kWh ya gezi leri tirhisiwaka hiku tirhisa xivumbeko xokarhi xa MEA, hi mol/kWh. Yi hlayeriwa kuya hi current density, cell voltage xikan’we na Faraday efficiency ehansi ka swiyimo swokarhi swa ntirho.
Hlela nhlayo ya formic acid leyi oxidized eka anode kuya hi mass balance hinkwayo. Ti reaction tinharhu leti phikizanaka ti humelela eka cathode: hydrogen evolution, kuhungutiwa ka CO2 kuya eka CO, na kuhungutiwa ka CO2 kuya eka formic acid. Hikuva hi na endlelo ra formic acid oxidation e Anton, formic acid FE yinga avanyisiwa hi swiphemu swimbirhi: nhlengeleto wa formic acid na formic acid oxidation. Nhlayo hinkwayo ya vukulu yi nga tsariwa tanihi:
Hi tirhise GC ku pima nhlayo ya formic acid, hydrogen, na CO leswi hlengeletiweke hi HPLC. Swifanele ku xiyiwa leswaku vunyingi bya formic acid byi hlengeletiwile kusuka eka anode hiku tirhisa setup leyi kombisiweke eka Supplementary Figure S5. Nhlayo ya formate leyi hlengeletiweke kusuka eka cathode chamber ayi na nkoka, kwalomu ka ti orders timbirhi ta vukulu ehansi, naswona yifika ehansi ka 0.5% wa nhlayo hinkwayo ya SC.
Modele wa vutleketli lebyi yaka emahlweni lowu tirhisiweke laha wu sekeriwe eka ntirho wa khale eka tisisiteme leti fanaka34. Endlelo leri hlanganisiweke ra swiringaniso swa Poisson-Nerst-Planck (PNP) ri tirhisiwa ku kumisisa nhlayo ya mati na vuswikoti bya electrostatic eka swiphemu leswi fambisaka hi ndlela ya elektroniki na ionic. Nkatsakanyo wa vuxokoxoko bya swiringaniso swa le hansi na geometry ya modele wu nyikiwile eka SI.
Endlelo leri ri kumisisa nhlayo ya swilo swa mati swa tsevu (\({{{{{{{\rm{C}}}}}}}{{{{{{\rm{O}}}}}}}}_{2 \left ({{{{{{\rm{aq}}}}}\right)}\), \({{{{{{{\rm{H}}}}}}}}^{+ }\ ), \ ({{{{{{\rm{O}}}}}}{{{{{{{\rm{H}}}}}}^{-}\), \({{{ {{{ \rm{ HCO}}}}}}}}_{3}^{-}\), \({{{{{{\rm{CO}}}}}}_{3}^{ 2-} \ ),\ ({{{{{\rm{HCOOH}}}}}}\), \({{{{{{\rm{HCOO}}}}}}}}^{- }\) na \({{{ {{{\rm{K}}}}}}^{+}\)), vuswikoti bya electrostatic eka xiyenge xo fambisa ionic (\({\phi }_{I}\ )) na vufambisi bya tielektroni ta anodic na cathodic. Swihlawulekisi swa gezi eka swiyenge (\({\phi }_{A}\) na \({\phi }_{C}\) hi ku landzelelana). Ematshan’wini ya sweswo, hambi kuri vukalatlhelo bya gezi bya ndzhawu kumbe mintirho ya ku hangalasiwa ka chaji aswi tiveki, ndzhawu ya chaji ya xibakabaka yi tlhantlhiwa hiku kongoma hiku tirhisa xiringaniso xa Poisson; Endlelo leri ri hi pfumelela ku modela hi ku kongoma switandzhaku swa Donnan repulsion eka swihlanganisi swa CEM|AEM, CEM|Pore, na AEM|Pore. Ku engetela kwalano, porous electrode theory (PET) yitirhisiwa ku hlamusela ku fambisiwa ka charge eka ti anodic na cathodic layers ta catalyst. Hi ku ya hi vutivi bya vatsari, ntirho lowu wu yimela ku tirhisiwa ko sungula ka PET eka tisisiteme leti nga na swifundzha swo tala swa xibalo xa xibakabaka.
Tisampulu ta GDE BOT na EOT cathode ti kamberiwile hiku tirhisa Zeiss Xradia 800 Ultra leyingana 8.0 keV ya xihlovo xa X-ray, absorption na wide field modes, na image fusion1. Swifaniso swa 901 swi hlengeletiwile kusuka eka -90° kuya eka 90° hi nkarhi wo paluxeka wa 50 wa tisekoni. Ku pfuxetiwa ku endliwile hiku tirhisa back projection filter leyingana voxel size ya 64 nm. Nxopaxopo wa ku avanyisa na ku hangalasiwa ka vukulu bya swiphemuphemu wu endliwile hi ku tirhisa khodi leyi tsariweke hi ndlela yo hlawuleka.
Ku hlawuriwa ka swihlawulekisi swa electron microscopic swikatsa ku nghenisa ti MEA ta xikambelo eka epoxy resin ku lulamisela ku tsemiwa ka ultrathin hi banga ra dayimani. Xiphemu xo tsemakanya xa MEA yin’wana na yin’wana xi tsemiwile kuya eka ku enta ka 50 kuya eka 75 nm. Microscope ya electron yo hundzisela ya Talos F200X (Thermo Fisher Scientific) yitirhisiwile eka mipimo ya scanning transmission electron microscopy (STEM) na energy-dispersive X-ray spectroscopy (EDS). Microscope yi hlomisiwile hi EDS Super-X system leyingana 4 wa ti windowless SDD detectors naswona yitirha hi 200 kV.
Tipheteni ta powder X-ray diffraction (PXRD) ti kumiwile eka Bruker Advance D8 powder X-ray diffractometer leyingana Ni-filtered Cu Kα radiation leyi tirhaka eka 40 kV na 40 mA. Ndzhawu ya scanning yisuka eka 10° kuya eka 60°, vukulu bya goza i 0.005°, naswona rivilo ro kuma data i 1 second hi goza.
RAS spectrum emakumu ka Bi2O3 Bi L3 catalyst yi pimiwe tani hi ntirho wa potential hiku tirhisa cell leyi endliweke ekaya. Bi2O3 catalytic ionomer ink yi lulamisiwile hiku tirhisa 26.1 mg Bi2O3 leyi pfanganisiweke na 156.3 μL ionomer solution (6.68%) naswona yi neutralized na 1 M KOH, mati (157 μL) na isopropyl alcohol (104 μL) kuva ku kumiwa inki ya ionomer. Xiringaniso xa catalyst i 0.4. Inki yi cheriwile eka maphepha ya graphene eka tindzhawu ta rectangular (10×4 mm) kufikela loko Bi2O3 catalyst loading yifika eka 0.5 mg/cm2. Xiphemu lexin’wana xa graphene xi cheriwa Kapton kuva xi hambanyisa tindzhawu leti kusuka eka electrolyte. Xiphepherhele xa graphene lexi funengetiweke hi catalyst xi nghenisiwile exikarhi ka ti PTFE timbirhi naswona xi khomiwile eka miri wa sele (PEEK) hi swikwirikiri, Xifaniso xa S8. Hg/HgO (1 M NaOH) yi tirhile tani hi electrode ya reference, naswona phepha ra carbon ri tirhile tani hi counter electrode. Electrode ya reference ya Hg/HgO yi kalibisiwile hiku tirhisa waya wa platinum lowu nghenisiweke eka hydrogen-saturated 0.1 M KOH ku hundzula ti potentials hinkwato leti pimiweke kuya eka reversible hydrogen electrode (RHE) scale. XRD spectra yikumeke hiku langutisisa vuswikoti bya Bi2O3/graphene sheet working electrode leyi nghenisiweke eka 0.1 M KOH, leyi hisiweke kuya eka 30 °C. Electrolyte yi rhendzeleka eka betri, laha ku nghenaka electrolyte ehansi ka sele kasi laha ku humaka kona e henhla ku tiyisisa leswaku electrolyte yi hlangana na catalyst layer loko ku vumbiwa ti bubbles. Ku tirhisiwile potentiostat ya CH Instruments 760e ku lawula vuswikoti bya electrode lebyi tirhaka. Ntlhandlamano wa vuswikoti a ku ri vuswikoti bya xirhendzevutani lexi pfulekeke: -100, -200, -300, -400, -500, -800, -850, -900, -1000, -1100, -1500 na +700 mV ku ya hi RHE. Ti potentials hinkwato ta iR ti lulamisiwile.
Bi L3 edge (~13424 eV for Bi metal) X-ray absorption fine structure (XAFS) spectroscopy yi endliwile eka channel 10-ID, Xihlovo xa Photon xa le Henhla (APS), Argonne National Fluorescence Laboratory. Laboratori ya Rixaka ya ku Pima Xikombiso. Ku tirhisiwe two-crystal Si(111) monochromator leyi titimelaka hi liquid nitrogen ku tune matimba ya X-ray, naswona xivoni lexi funengetiweke hi rhodium xi tirhisiwile ku hunguta harmonic content. Ti scan energies ti cinciwile kusuka eka 13200 kuya eka 14400 eV, naswona fluorescence yi pimiwe hiku tirhisa 5 × 5 silicon PIN diode array leyinga hava ti filters kumbe Soller slits. Enerji yo tsemakanya ya zero ya derivative ya vumbirhi yi kalibiwa eka 13271.90 eV hiku tirhisa L2 edge ya Pt foil. Hikwalaho ka ku enta ka sele ya electrochemical, a swi nga koteki ku pima hi nkarhi wun’we spectrum ya reference standard. Xisweswo, ku cinca loku hlayiweke ka scan-to-scan eka matimba ya X-rheyi leyi humelelaka i ±0.015 eV leyi sekeriweke eka mimpimo leyi phindha-phindhiweke eka xikambelo hinkwaxo. Ku enta ka Bi2O3 layer swiyisa eka mpimo wokarhi wa self-absorption ya fluorescence; ti electrode ti hlayisa orientation leyi nga cinciki loko yi pimanisiwa na incident beam na detector, leswi endlaka leswaku swikeni hinkwaswo swifana swinene. Near-field XAFS spectrum yitirhisiwile ku kumisisa xiyimo xa oxidation na xivumbeko xa tikhemikhali xa bismuth hiku pimanisiwa na ndzhawu ya XANES ya Bi na Bi2O3 standards hiku tirhisa linear combination fitting algorithm ya Athena software (version 0.9.26). hi khodi ya IFEFFIT 44.
Data leyi seketelaka tinhlayo eka xitsalwana lexi na mahetelelo man’wana ya ndzavisiso lowu ya kumeka eka mutsari loyi a fambelanaka na yena hi xikombelo lexi twalaka.
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