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Ukwehliswa kwe-carbon dioxide nge-electrochemical ibe yi-formic acid kuyindlela ethembisayo yokuthuthukisa ukusetshenziswa kwe-carbon dioxide futhi kunezinhlelo zokusebenza ezingaba khona njengendawo yokugcina i-hydrogen. Kulo msebenzi, kwakhiwa ukwakheka kwe-electrode ye-membrane ye-zero-gap ukuze kuhlanganiswe i-formic acid ngqo kusuka ku-carbon dioxide. Intuthuko ebalulekile kwezobuchwepheshe yi-forated cation exchange membrane, lapho, uma isetshenziswa ekucushweni kwe-bipolar membrane ebheke phambili, ivumela i-formic acid eyakhiwe esibonakalayo se-membrane ukuthi isuswe ngensimu yokugeleza kwe-anodic ngamanani aphansi njengo-0.25 M. Ngaphandle kwezingxenye ezengeziwe ze-sandwich phakathi kwe-anode ne-cathode, lo mqondo uhlose ukusebenzisa izinto zebhethri ezikhona kanye nemiklamo evamile kumaseli kaphethiloli kanye ne-hydrogen electrolysis, okuvumela ukushintshela okusheshayo ekukhulisweni nasekuthengisweni. Esitokisini esingu-25 cm2, ukucushwa kwe-forated cation exchange membrane kunikeza ukusebenza kahle kwe-Faraday okungu->75% kwe-formic acid ku-<2 V kanye no-300 mA/cm2. Okubaluleke kakhulu, ukuhlolwa kokuzinza kwamahora angu-55 ku-200 mA/cm2 kubonise ukusebenza kahle kwe-Faraday okuzinzile kanye ne-voltage yeseli. Ukuhlaziywa kobuchwepheshe-kwezomnotho kusetshenziselwa ukubonisa izindlela zokufeza ukulingana kwezindleko nezindlela zamanje zokukhiqiza i-formic acid.
Ukwehliswa kwe-carbon dioxide nge-electrochemical ibe yi-formic acid kusetshenziswa ugesi ovuselelekayo kuye kwabonakala kunciphisa izindleko zokukhiqiza ngamaphesenti angama-75 uma kuqhathaniswa nezindlela zendabuko ezisekelwe kuphethiloli. Njengoba kuboniswe ezincwadini2,3, i-formic acid inezinhlobo eziningi zezicelo, kusukela endleleni ephumelelayo neyongayo yokugcina nokuthutha i-hydrogen iye endaweni yokudla yemboni yamakhemikhali4,5 noma imboni ye-biomass6. I-Formic acid iye yabonakala ngisho nanjenge-feedstock yokuguqulwa okulandelayo ibe yi-jet fuel intermediates eqhubekayo kusetshenziswa ubunjiniyela be-metabolic7,8. Ngokuthuthuka kwe-formic acid economics1,9, imisebenzi eminingana yocwaningo igxile ekwenzeni ngcono ukukhetha kwe-catalyst10,11,12,13,14,15,16. Kodwa-ke, imizamo eminingi iyaqhubeka nokugxila kumaseli amancane e-H noma amaseli okugeleza koketshezi asebenza ngobuningi bamanje obuphansi (<50 mA/cm2). Ukuze kuncishiswe izindleko, kufezwe ukuthengiswa futhi kwandiswe ukungena emakethe okulandelayo, ukunciphisa i-carbon dioxide nge-electrochemical (CO2R) kumele kwenziwe ngobuningi bamanje obuphezulu (≥200 mA/cm2) kanye nokusebenza kahle kwe-Faraday (FE)17 ngenkathi kwandiswa ukusetshenziswa kwezinto kanye nokusebenzisa izingxenye zebhethri ezivela kumaseli kaphethiloli we-Technology kanye ne-electrolysis yamanzi kuvumela amadivayisi e-CO2R ukuthi asebenzise amandla ezomnotho esikalini18. Ngaphezu kwalokho, ukuze kwandiswe ukusetshenziswa komkhiqizo futhi kugwenywe ukucutshungulwa okwengeziwe okungezansi, i-formic acid kufanele isetshenziswe njengomkhiqizo wokugcina kunokuba kwenziwe usawoti we-formate19.
Kulesi siqondiso, kwenziwe imizamo yakamuva yokuthuthukisa amadivayisi e-CO2R afanele embonini e-formate/formic acid based gas diffusion electrode (GDE). Ukubuyekezwa okuphelele kukaFernandez-Caso et al.20 kufingqa zonke izilungiselelo zamaseli e-electrochemical zokunciphisa okuqhubekayo kwe-CO2 ibe yi-formic acid/formate. Ngokuvamile, zonke izilungiselelo ezikhona zingahlukaniswa ngezigaba ezintathu eziyinhloko: 1. Ama-catholytes agelezayo19,21,22,23,24,25,26,27, 2. I-membrane eyodwa (i-cation exchange membrane (CEM)28 noma i-anion exchange membrane (AEM)29 kanye no-3. Ukucushwa kwe-sandwich15,30,31,32. Izingxenye ezilula zalezi zilungiselelo ziboniswe ku-Figure 1a. Ukuze kulungiselelwe ukugeleza kwe-catholyte, kudalwa igumbi le-electrolyte phakathi kwe-membrane kanye ne-cathode ye-GDE. I-catholyte egelezayo isetshenziselwa ukudala iziteshi ze-ion kungqimba lwe-catholyte lwe-catalyst33, yize isidingo sayo sokulawula ukukhetha kwe-formate sixoxwa ngakho34. Kodwa-ke, lokhu kucushwa kwasetshenziswa nguChen et al. Besebenzisa i-catholyte ye-SnO2 ku-carbon substrate enengqimba ye-catholyte engu-1.27 mm ubukhulu, kufike ku-90% FE 35 ku-500 mA/cm2 kwafezwa. Ukuhlanganiswa kwengqimba ye-catholyte ejiyile kanye ne-reverse-biased bipolar membrane (BPM) ekhawulela ukudluliselwa kwe-ion inikeza i-voltage yokusebenza engu-6 V kanye nokusebenza kahle kwamandla okungu-15%. Ukuze kuthuthukiswe ukusebenza kahle kwamandla, uLi et al., besebenzisa ukucushwa kwe-CEM eyodwa, bathole i-FE 29 engu-93.3% ku-fractional current density engu-51.7 mA/cm2. UDiaz-Sainz et al.28 basebenzise umshini wokuhlunga one-membrane eyodwa ye-CEM ku-current density engu-45 mA/cm2. Kodwa-ke, zonke izindlela zakhiqiza i-formate esikhundleni somkhiqizo okhethwayo, i-formic acid. Ngaphezu kwezidingo ezengeziwe zokucubungula, ekucushweni kwe-CEM, amafomethi afana ne-KCOOH angaqongelela ngokushesha ensimini ye-GDE kanye nokugeleza, okubangela imikhawulo yokuhamba kanye nokwehluleka kwamaseli ekugcineni.
Ukuqhathaniswa kwe-CO2R ezintathu ezivelele kakhulu ekucushweni kwedivayisi yokuguqulwa kwe-formate/formic acid kanye nokwakheka okuphakanyisiwe kulolu cwaningo. b Ukuqhathaniswa kwesivuno se-total current kanye ne-formate/formic acid sokulungiswa kwe-catholyte, ukucushwa kwe-sandwich, ukucushwa kwe-single CEM ezincwadini (okuboniswe kuThebula Elingeziwe S1) kanye nomsebenzi wethu. Amamaki avulekile abonisa ukukhiqizwa kwesisombululo se-formate, kanti amamaki aqinile abonisa ukukhiqizwa kwe-formate acid. *Ukucushwa kuboniswe kusetshenziswa i-hydrogen ku-anode. c Ukucushwa kwe-Zero-gap MEA kusetshenziswa i-composite bipolar membrane ene-perforated cation exchange layer esebenza kwimodi ye-forward bias.
Ukuze kuvinjelwe ukwakheka kwe-formate, uProietto nabanye 32 basebenzise ukucushwa kwe-splitless filter press lapho amanzi angenawo i-ion ageleza khona phakathi kwe-interlayer. Uhlelo lungafinyelela ku->70% CE kububanzi bamanje be-density obungu-50–80 mA/cm2. Ngokufanayo, uYang nabanye 14 baphakamise ukusetshenziswa kwe-solid electrolyte interlayer phakathi kwe-CEM ne-AEM ukukhuthaza ukwakheka kwe-formic acid. UYang nabanye 31,36 bathole i-91.3% FE kuseli elingu-5 cm2 ku-200 mA/cm2, bakhiqiza isixazululo se-formic acid esingu-6.35 wt%. UXia nabanye 32 Besebenzisa ukucushwa okufanayo, ukuguqulwa kwe-carbon dioxide (CO2) okungu-83% ku-formic acid FE kwafezwa ku-200 mA/cm2, futhi ukuqina kohlelo kwahlolwa amahora ayi-100 nemizuzu engama-30. Nakuba imiphumela emincane ithembisa, izindleko ezikhulayo kanye nobunzima be-resin yokushintshana kwama-ion anezimbobo kwenza kube nzima ukukhulisa ukucushwa kwe-interlayer kuya ezinhlelweni ezinkulu (isb., 1000 cm2).
Ukuze sibone umphumela wemiklamo ehlukene, sibhale phansi ukukhiqizwa kwe-formate/formic acid nge-kWh yazo zonke izinhlelo okukhulunywe ngazo ngaphambili futhi sazidweba ku-Figure 1b. Kusobala lapha ukuthi noma yiluphi uhlelo oluqukethe i-catholyte noma i-interlayer luzofinyelela phezulu ekusebenzeni kwalo ekuminyaneni kwamanje okuphansi futhi luwohloke ekuminyaneni kwamanje okuphezulu, lapho umkhawulo we-ohmic unganquma khona i-voltage yeseli. Ngaphezu kwalokho, yize ukucushwa kwe-CEM okusebenzisa amandla okwanele kunikeza ukukhiqizwa kwe-molar formic acid ephezulu kakhulu nge-kWh, ukwakheka kukasawoti kungaholela ekuwohlokeni kokusebenza okusheshayo ekuminyaneni kwamanje okuphezulu.
Ukuze sinciphise izindlela zokuhluleka ebesixoxa ngazo ngaphambilini, sakha i-membrane electrode assembly (MEA) equkethe i-composite forward biased BPM ene-perforated cation exchange membrane (PCEM). Ukwakheka kwayo kuboniswe ku-Figure 1c. I-Hydrogen (H2) ifakwa ku-anode ukuze ikhiqize ama-proton ngokusebenzisa i-hydrogen oxidation reaction (HOR). Isendlalelo se-PCEM sifakwa ohlelweni lwe-BPM ukuze kuvunyelwe ama-ion e-formate akhiqizwe ku-cathode ukuthi adlule ku-AEM, ahlanganiswe nama-proton ukuze akhe i-formic acid ku-interface ye-BPM kanye nama-interstitial pores e-CEM, bese ephuma nge-GDE anode kanye nensimu yokugeleza. Sisebenzisa lokhu kulungiselelwa, sithole i-FE engu->75% ye-formic acid ku-<2 V kanye ne-300 mA/cm2 endaweni yeseli engu-25 cm2. Okubaluleke kakhulu, umklamo usebenzisa izingxenye ezitholakala kwezentengiselwano kanye nezakhiwo zehadiwe zezitshalo ze-fuel cell kanye ne-water electrolysis, okuvumela isikhathi esisheshayo sokulinganisa. Ukulungiselelwa kwe-Catholyte kuqukethe amakamelo okugeleza kwe-catholyte okungabangela ukungalingani kwengcindezi phakathi kwezigaba zegesi kanye noketshezi, ikakhulukazi ekulungiselelweni kwamaseli amakhulu. Kwizakhiwo zesandwich ezinezendlalelo ezinezimbobo zokugeleza koketshezi, kudingeka imizamo emikhulu yokwenza ngcono ungqimba oluphakathi olunezimbobo ukunciphisa ukwehla kwengcindezi kanye nokuqongelela kwe-carbon dioxide ngaphakathi kwesendlalelo esiphakathi. Zombili lezi zinto zingaholela ekuphazamisekeni kokuxhumana kwamaselula. Kunzima futhi ukukhiqiza izendlalelo ezincane ezinezimbobo ezizimele ngezinga elikhulu. Ngokuphambene nalokho, ukucushwa okusha okuphakanyisiwe kuwukucushwa kwe-MEA okungenayo i-zero-gap okungenalo igumbi lokugeleza noma ungqimba oluphakathi. Uma kuqhathaniswa namanye amaseli e-electrochemical akhona, ukucushwa okuphakanyisiwe kuhlukile ngoba kuvumela ukuhlanganiswa okuqondile kwe-formic acid ekucushweni okunwebekayo, okusebenzisa amandla kahle, kanye ne-zero-gap.
Ukuze kucindezelwe ukuvela kwe-hydrogen, imizamo emikhulu yokunciphisa i-CO2 isebenzise ukwakheka kwe-MEA kanye ne-AEM membrane kuhlanganiswe nama-electrolyte aphezulu okugcwala kwe-molar (isb., 1-10 M KOH) ukudala izimo ze-alkaline ku-cathode (njengoba kuboniswe ku-Figure 2a). Kulezi zilungiselelo, ama-ion e-formate akhiwe ku-cathode adlula ku-membrane njengezinhlobo ezishajelwe kabi, bese kwakheka i-KCOOH bese iphuma ohlelweni ngomfudlana we-anodic KOH. Nakuba i-formate FE kanye ne-voltage yeseli ekuqaleni kwakulungile njengoba kuboniswe ku-Figure 2b, ukuhlolwa kokuqina kwaholela ekunciphiseni i-FE cishe ngo-30% emahoreni ayi-10 kuphela (Figure S1a–c). Kufanele kuqashelwe ukuthi ukusetshenziswa kwe-anolyte ye-1 M KOH kubalulekile ukunciphisa i-anodic overvoltage ezinhlelweni ze-alkaline oxygen evolution reaction (OER)37 nokufeza ukufinyeleleka kwe-ion ngaphakathi kwe-cathode catalyst bed33. Uma ukuhlushwa kwe-anolyte kwehliswa ku-0.1 M KOH, kokubili i-voltage yeseli kanye ne-formic acid oxidation (ukulahlekelwa yi-formic acid) kuyanda (Isithombe S1d), okubonisa ukuhweba kwe-zero-sum. Izinga le-formate oxidation lihlolwe kusetshenziswa ibhalansi yesisindo iyonke; ukuthola imininingwane eyengeziwe, bheka isigaba esithi “Izindlela”. Ukusebenza kusetshenziswa i-MEA kanye nokulungiselelwa kwe-single CEM membrane nakho kwafundwa, futhi imiphumela iboniswe ku-Figure S1f,g. I-FE formate eqoqwe ku-cathode yayingu->60% ku-200 mA/cm2 ekuqaleni kokuhlolwa, kodwa yonakala ngokushesha zingakapheli amahora amabili ngenxa yokuqongelela usawoti we-cathode okuxoxwe ngakho ngaphambilini (Isithombe S11).
I-Schematic ye-zero-gap MEA ene-CO2R ku-cathode, i-hydrogen oxidation reaction (HOR) noma i-OER ku-anode, kanye ne-membrane eyodwa ye-AEM phakathi. b I-FE kanye ne-voltage yeseli yalokhu kulungiselelwa nge-1 M KOH kanye ne-OER egeleza ku-anode. Amabha amaphutha amelela ukuphambuka okujwayelekile kwezilinganiso ezintathu ezahlukene. ku-FE kanye ne-voltage yeseli yesistimu ene-H2 kanye ne-HOR ku-anode. Imibala ehlukene isetshenziselwa ukuhlukanisa ukukhiqizwa kwe-formate kanye ne-formic acid. d Umdwebo we-Schematic we-MEA one-BPM ushintshelwe phambili phakathi. I-FE kanye ne-voltage yebhethri uma kuqhathaniswa nesikhathi ku-200 mA/cm2 kusetshenziswa lokhu kulungiselelwa. f Isithombe esinqamula isigaba se-BPM MEA ebheke phambili ngemuva kokuhlolwa okufushane.
Ukuze kukhiqizwe i-formic acid, i-hydrogen inikezwa ku-catalyst ye-Pt-on-carbon (Pt/C) ku-anode. Njengoba kuboniswe ku-Figure 2d, ama-proton akhiqiza i-BPM abheke phambili ku-anode ahlolwe ngaphambilini ukuze kufezwe ukukhiqizwa kwe-formic acid. Iyunithi yokulungisa i-BPM yehlulekile ngemuva kwemizuzu engama-40 yokusebenza ku-current engu-200 mA/cm2, ehambisana nokwanda kwamandla kagesi angaphezu kuka-5 V (Fig. 2e). Ngemuva kokuhlola, ukuhlukanisa okusobala kwabonwa ku-interface ye-CEM/AEM. Ngaphandle kwe-formate, ama-anion anjenge-carbonate, i-bicarbonate kanye ne-hydroxide nawo angadlula ku-membrane ye-AEM futhi asabela nama-proton ku-interface ye-CEM/AEM ukukhiqiza igesi ye-CO2 namanzi aketshezi, okuholela ku-BPM delamination (Fig. 2f) kanye no-, ekugcineni okuholela ekuhlulekeni kweseli.
Ngokusekelwe ekusebenzeni nasekuhlulekeni kwezindlela zokucushwa okungenhla, kuphakanyiswa ukwakheka okusha kwe-MEA njengoba kuboniswe kuMfanekiso 1c futhi kuchazwe kabanzi kuMfanekiso 3a38. Lapha, ungqimba lwe-PCEM lunikeza indlela yokufuduka kwe-formic acid nama-anion kusuka ku-interface ye-CEM/AEM, ngaleyo ndlela kuncishiswe ukuqongelela kwento. Ngesikhathi esifanayo, indlela ye-PCEM interstitial iqondisa i-formic acid ensimini yokusabalalisa kanye nensimu yokugeleza, kunciphisa amathuba okuthi i-formic acid oxidation ivele. Imiphumela ye-polarization isebenzisa ama-AEM anobukhulu obungu-80, 40 no-25 mm iboniswe kuMfanekiso 3b. Njengoba kulindelekile, yize i-voltage yamaseli iyonke ikhuphuka ngokuqina kwe-AEM okwandayo, ukusebenzisa i-AEM ejiyile kuvimbela ukusabalala kwe-formic acid emuva, ngaleyo ndlela kwandiswe i-cathode pH futhi kuncishiswe ukukhiqizwa kwe-H2 (Umfanekiso 3c–e).
a Umfanekiso wesakhiwo se-MEA esine-AEM kanye ne-CEM ebhoboziwe kanye nezindlela ezahlukene zokuthutha i-formic acid. b I-voltage yeseli ekujuleni kwamanje okuhlukene kanye nobukhulu be-AEM obuhlukene. ku-EE ekujuleni kwamanje okuhlukahlukene okunobukhulu be-AEM obungu-80 μm (d) 40 μm, e) 25 μm. Amabha amaphutha amelela ukuphambuka okujwayelekile okulinganiswe kusuka kumasampula amathathu ahlukene. f Imiphumela yokulingisa yokuhlushwa kwe-formic acid kanye nenani le-pH esibonakalayo se-CEM/AEM ekujuleni kwe-AEM okuhlukile. f I-PC kanye ne-pH kungqimba lwe-cathode lwe-catalyst enobukhulu befilimu ye-AEM obuhlukene. g Ukusatshalaliswa kwezinhlangothi ezimbili kokuhlushwa kwe-formic acid ngesibonisi se-CEM/AEM kanye nokubhoboza.
Isithombe S2 sibonisa ukusatshalaliswa kokuhlushwa kwe-formic acid kanye ne-pH kulo lonke ubukhulu be-MEA kusetshenziswa i-Poisson-Nernst-Planck finite element modeling. Akumangazi ukuthi ukuhlushwa okuphezulu kwe-formic acid, 0.23 mol/L, kubonakala ku-interface ye-CEM/AEM, njengoba i-formic acid yakheka kulesi sixhumanisi. Ukuhlushwa kwe-formic acid nge-AEM kwehla ngokushesha njengoba ukuhlushwa kwe-AEM kukhuphuka, okubonisa ukumelana okukhulu nokudluliselwa kwesisindo kanye nokugeleza okuncane kwe-formic acid ngenxa yokusabalala komhlane. Izibalo 3 f kanye no-g zibonisa amanani e-pH kanye ne-formic acid ​​ku-cathode catalyst bed okubangelwa ukusabalala komhlane kanye nokusatshalaliswa kwe-formic acid okunezinhlangothi ezimbili, ngokulandelana. Uma i-membrane ye-AEM inciphile, kulapho ukuhlushwa kwe-formic acid kukhuphuka eduze kwe-cathode, futhi i-pH ye-cathode iba ne-acidic. Ngakho-ke, yize ama-membrane e-AEM ajiyile ephumela ekulahlekelweni okuphezulu kwe-ohmic, abalulekile ekuvimbeleni ukusabalala komhlane kwe-formic acid ku-cathode nokukhulisa ubumsulwa obuphezulu bohlelo lwe-FE formic acid. Ekugcineni, ukwandisa ubukhulu be-AEM bube ngu-80 μm kwaholela ku-FE >75% ye-formic acid ku-<2 V kanye no-300 mA/cm2 endaweni yeseli engu-25 cm2.
Ukuze kuhlolwe ukuzinza kwalolu hlobo lokwakheka olusekelwe ku-PECM, amandla ebhethri agcinwe ku-200 mA/cm2 amahora angu-55. Imiphumela iyonke iboniswe ku-Figure 4, nemiphumela evela emahoreni okuqala angu-3 iqokonyiswe ku-Figure S3. Lapho usebenzisa i-Pt/C anodic catalyst, i-voltage yeseli yanda kakhulu phakathi nemizuzu yokuqala engu-30 (Figure S3a). Esikhathini eside, i-voltage yeseli yahlala ifana, okuhlinzeka ngesilinganiso sokuwohloka esingu-0.6 mV/h (Fig. 4a). Ekuqaleni kokuhlolwa, i-PV ye-formic acid eqoqwe ku-anode yayingu-76.5% kanti i-PV ye-hydrogen eqoqwe ku-cathode yayingu-19.2%. Ngemva kwehora lokuqala lokuhlolwa, i-hydrogen FE yehle yaya ku-13.8%, okubonisa ukukhethwa kwe-formate okuthuthukisiwe. Kodwa-ke, izinga lokushiswa kwe-formic acid ohlelweni lehle laya ku-62.7% ngehora eli-1, kanti izinga lokushiswa kwe-anodic formic acid lenyuke lisuka cishe ku-zero ekuqaleni kokuhlolwa laya ku-17.0%. Ngemva kwalokho, i-FE ye-H2, i-CO, i-formic acid kanye nezinga lokushiswa kwe-anodic kwe-formic acid kwahlala kuzinzile ngesikhathi sokuhlolwa. Ukwanda kokushiswa kwe-formic acid phakathi nehora lokuqala kungase kube ngenxa yokuqongelela kwe-formic acid esibonakalayo se-PCEM/AEM. Njengoba ukuhlushwa kwe-formic acid kukhuphuka, akugcini nje ngokubhoboza kwe-membrane, kodwa futhi kuyasakazeka nge-FEM uqobo futhi kungene kungqimba lwe-anode lwe-Pt/C. Njengoba i-formic acid iyi-liquid ku-60°C, ukuqongelela kwayo kungabangela izinkinga zokudlulisa isisindo futhi kuholele ekushisweni okukhethwayo kune-hydrogen.
a I-voltage yeseli uma iqhathaniswa nesikhathi (200 mA/cm2, 60 °C). I-insert ikhombisa isithombe se-optical microscope se-cross-section ye-MEA ene-EM enezimbobo. Ibha yesikali: 300 µm. b Ubumsulwa be-PE kanye ne-formic acid njengomsebenzi wesikhathi ku-200 mA/cm2 kusetshenziswa i-anode ye-Pt/C.
Ukwakheka kwamasampula ekuqaleni kokuhlolwa (i-BOT) ngesikhathi sokulungiselela kanye nasekupheleni kokuhlolwa (i-EOT) ngemva kwamahora angu-55 okuhlolwa kokuzinza kwachazwa kusetshenziswa i-nano-X-ray computed tomography (i-nano-CT), njengoba kuboniswe kuMfanekiso 5 a. Isampula ye-EOT inosayizi omkhulu wezinhlayiya ze-catalyst onobubanzi obungu-1207 nm uma kuqhathaniswa no-930 nm we-BOT. Izithombe ze-high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) kanye nemiphumela ye-energy-dispersive X-ray spectroscopy (EDS) ziboniswe kuMfanekiso 5b. Ngenkathi ungqimba lwe-BOT catalyst luqukethe iningi lezinhlayiya ze-catalyst ezincane kanye nama-agglomerate amakhulu, esigabeni se-EOT ungqimba lwe-catalyst lungahlukaniswa lube yizifunda ezimbili ezihlukene: esinye esinezinhlayiya eziqinile ezinkulu kakhulu kanti esinye sinezindawo ezinezinhlayiya eziningi. Inani lezinhlayiya ezincane. Isithombe se-EDS sibonisa ukuthi izinhlayiya ezinkulu eziqinile zicebile ku-Bi, mhlawumbe i-metallic Bi, kanti izifunda ezinezinhlayiya zicebile ngomoya-mpilo. Uma iseli lisebenza ku-200 mA/cm2, amandla angemahle e-cathode azobangela ukwehla kwe-Bi2O3, njengoba kufakazelwa yimiphumela ye-in situ X-ray absorption spectroscopy okuxoxwe ngayo ngezansi. Imiphumela yemephu ye-HAADF-STEM kanye ne-EDS ikhombisa ukuthi i-Bi2O3 idlula enkambisweni yokunciphisa, okubangela ukuthi ilahlekelwe yi-oxygen futhi ihlangane ibe yizinhlayiya ezinkulu zensimbi. Amaphethini e-X-ray diffraction ama-cathode e-BOT ne-EOT aqinisekisa ukuchazwa kwedatha ye-EDS (Umfanekiso 5c): i-Bi2O3 ekristalu kuphela etholakale ku-cathode ye-BOT, kanti i-bimetal ekristalu etholakale ku-cathode ye-EOT. Ukuze kuqondwe umphumela we-cathode potential esimweni se-oxidation se-cathode ye-Bi2O3 ye-Bi2O3, izinga lokushisa lahlukahluka kusukela ku-open circuit potential (+0.3 V vs RHE) kuya ku--1.5 V (vs RHE). Kuqashelwe ukuthi isigaba se-Bi2O3 siqala ukwehla ku--0.85 V uma kuqhathaniswa ne-RHE, futhi ukwehla kwamandla omugqa omhlophe esifundeni somphetho we-spectrum kubonisa ukuthi i-Bi yensimbi yehliswe yaba ngu-90% we-RHE ku--1.1. V ngokumelene ne-RHE (Isithombe 5d). Kungakhathaliseki ukuthi inqubo injani, ukukhetha okuphelele kwe-forme ku-cathode akukashintshi, njengoba kucatshangwa kusukela ku-H2 kanye ne-CO FE kanye nokwakheka kwe-formic acid, naphezu kwezinguquko ezibalulekile ku-morphology ye-cathode, isimo se-catalyst oxidation, kanye nesakhiwo se-microcrystalline.
a Isakhiwo esinezinhlangothi ezintathu sesendlalelo se-catalyst kanye nokusatshalaliswa kwezinhlayiya ze-catalyst ezitholakala kusetshenziswa i-nano-X-ray CT. Ibha yesikali: 10 µm. b Okuphezulu 2: Izithombe ze-HAADF-STEM zezingqimba ze-cathode ze-BOT kanye ne-EOT catalysts. Ibha yesikali: 1 µm. Ngaphansi 2: Izithombe ze-HADF-STEM ezikhulisiwe kanye nezithombe ze-EDX zesendlalelo se-cathode se-EOT catalyst. Ibha yesikali: 100 nm. c Amaphethini e-X-ray diffraction amasampula e-BOT kanye ne-EOT cathode. d I-In situ X-ray absorption spectra ye-Bi2O3 electrode ku-0.1 M KOH njengomsebenzi we-potential (0.8 V kuya ku--1.5 V vs. RHE).
Ukuze kutholakale ukuthi yimaphi amathuba akhona okuthuthukisa ukusebenza kahle kwamandla ngokuvimbela i-formic acid oxidation, kusetshenziswe i-H2 reference electrode ukuhlonza umnikelo wokulahleka kwe-voltage39. Ku-current densities engaphansi kuka-500 mA/cm2, i-cathode potential ihlala ingaphansi kuka--1.25 V. I-anodic potential ihlukaniswe izingxenye ezimbili eziyinhloko: i-exchange current density HOR kanye ne-theory overvoltage HOR 40 eyabikezelwa yi-Bulter-Volmer equation eyalinganiswa ngaphambilini, kanti ingxenye esele ibangelwa i-oxidation formic acid. Ngenxa ye-reaction kinetics ehamba kancane kakhulu uma kuqhathaniswa ne-HOR41, izinga elincane le-formic acid oxidation reaction ku-anode lingabangela ukwanda okukhulu kwe-anodic potential. Imiphumela ikhombisa ukuthi ukuvinjelwa okuphelele kwe-formic acid anodic oxidation kungasusa cishe i-500 mV overvoltage.
Ukuze kuhlolwe lokhu kulinganisa, izinga lokugeleza kwamanzi angenawo i-ion (DI) endaweni yokungena ye-anode lahlukahluka ukuze kuncishiswe ukuhlushwa kwe-formic acid ephumayo. Izibalo 6b no-c zibonisa i-FE, ukuhlushwa kwe-formic acid, kanye ne-voltage yeseli njengomsebenzi we-DI flux ku-anode ku-200 mA/cm2. Njengoba izinga lokugeleza kwamanzi angenawo i-ion landa kusuka ku-3.3 mL/min kuya ku-25 mL/min, ukuhlushwa kwe-formic acid ku-anode kwehle kusuka ku-0.27 mol/L kuya ku-0.08 mol/L. Uma kuqhathaniswa, kusetshenziswa isakhiwo sesandwich esiphakanyiswe nguXia et al. 30 ukuhlushwa kwe-formic acid okungu-1.8 mol/L kwatholakala ku-200 mA/cm2. Ukunciphisa ukuhlushwa kuthuthukisa i-FE iyonke ye-formic acid futhi kunciphisa i-FE ye-H2 njengoba i-cathode pH iba yi-alkaline kakhulu ngenxa yokuncipha kokusabalala kwe-formic acid emuva. Ukwehla kokuhlushwa kwe-formic acid ekugelezeni okuphezulu kwe-DI nakho kuqede cishe i-formic acid oxidation, okuholela ku-voltage yeseli ephelele engaphansi kuka-1.7 V ku-200 mA/cm2. Izinga lokushisa lebhethri lithinta nokusebenza okuphelele, futhi imiphumela iboniswe kuMfanekiso S10. Kodwa-ke, izakhiwo ezisekelwe ku-PCEM zingathuthukisa kakhulu ukusebenza kahle kwamandla ekuvimbeleni i-formic acid oxidation, kungakhathaliseki ukuthi kusetshenziswa ama-catalyst anodic anokukhetha kwe-hydrogen okuthuthukisiwe ku-formic acid noma ngokusebenza kwedivayisi.
a Ukuqhekeka kwamandla kagesi eseli kusetshenziswa i-electrode ye-H2 yereferensi yeseli esebenza ku-60 °C, i-anode ye-Pt/C kanye ne-80 µm AEM. b Ukuhlushwa kwe-FE kanye ne-formic acid kuqoqwe ku-200 mA/cm2 kusetshenziswa amazinga okugeleza ahlukene amanzi a-anodic deionized. c Lapho i-anode iqoqa i-formic acid ngamanani ahlukene, i-voltage yeseli ingu-200 mA/cm2. Amabha amaphutha amelela ukuphambuka okujwayelekile kwezilinganiso ezintathu ezahlukene. d Intengo yokuthengisa encane ehlukaniswe ngokusebenza kwamazinga ahlukahlukene okugeleza kwamanzi a-deionized kusetshenziswa amanani kagesi aphakathi kwezimboni kazwelonke angu-US$0.068/kWh kanye ne-US$4.5/kg hydrogen. (*: Isimo esincane sokuxiliswa kwe-formic acid ku-anode sicatshangwa ukuthi siyi-10 M FA, isilinganiso sentengo kagesi yezimboni sikazwelonke siyi-$0.068/kWh, kanti i-hydrogen iyi-$4.5/kg. **: Isimo esincane sokuxiliswa kwe-oxidation yi-formic acid ecatshangwayo. Ukuhlushwa kwe-FA ku-anode kuyi-1.3 M anode, intengo kagesi elindelekile yesikhathi esizayo ingu-$0.03/kWh, kanti umugqa onamachashazi umelela intengo yemakethe engu-85 wt% FA.
Ukuhlaziywa kwezobuchwepheshe-kwezomnotho (i-TEA) kwenziwe ukuze kutholakale intengo yokuthengisa encane kakhulu yezinhlangano zikaphethiloli ngaphansi kwezimo ezahlukahlukene zokusebenza, njengoba kuboniswe kuMfanekiso 5d. Izindlela kanye nedatha yangemuva ye-TEA kungatholakala ku-SI. Lapho ukugcwala kwe-LC ku-anode exhaust kuphakeme, naphezu kwe-voltage ephezulu yamaseli, izindleko eziphelele zokuhlanganiswa kukaphethiloli ziyancishiswa ngenxa yokwehla kwezindleko zokuhlukanisa. Uma i-anodic oxidation ye-formic acid ingancishiswa ngokuthuthukiswa kwe-catalyst noma ubuchwepheshe be-electrode, inhlanganisela ye-voltage ephansi yamaseli (1.66 V) kanye nokugcwala okuphezulu kwe-FA emanzini angcolile (10 M) kunganciphisa izindleko zokukhiqiza i-electrochemical FA zibe yi-0.74 US dollars/kg (ngokusekelwe kugesi). intengo) $0.068/kWh kanye ne-$4.5/kg i-hydrogen42. Ngaphezu kwalokho, uma kuhlanganiswa nezindleko ezibikezelwe zesikhathi esizayo zikagesi ovuselelekayo ze-$0.03/kWh kanye ne-hydrogen ye-$2.3/kg, umgomo wamanzi angcolile we-FA wehliswa waba yizigidi ezingu-1.3, okuholela ekutheni izindleko zokukhiqiza zokugcina ezibikezelwe zibe yi-US$0.66/kg43. Lokhu kufana namanani emakethe amanje. Ngakho-ke, imizamo yesikhathi esizayo egxile ezintweni ze-electrode kanye nezakhiwo inganciphisa kakhulu i-anodization ngenkathi ivumela ukusebenza kuma-voltage aphansi weseli ukukhiqiza amazinga aphezulu e-LC.
Ngamafuphi, sifunde izakhiwo eziningana ze-ZERO-gap MEA zokunciphisa i-CO2 ibe yi-formic acid futhi saphakamisa isakhiwo esiqukethe i-composite forward-biased bipolar membrane ehlanganisa i-perforated cation exchange membrane (PECM) ukuze kube lula i-membrane mass transfer interface ye-formic acid ephumayo. . Lokhu kulungiselelwa kukhiqiza i-formic acid engaphezulu kuka-96% ekugxilweni okufika ku-0.25 M (ngesilinganiso sokugeleza kwe-anode DI esingu-3.3 mL/min). Ngamazinga aphezulu okugeleza kwe-DI (25 mL/min), lokhu kulungiselelwa kunikeze ubuningi bamanje obungu->80% FE obungu-200 mA/cm2 ku-1.7 V kusetshenziswa indawo yeseli engu-25 cm2. Ngamazinga aphakathi e-anodic DI (10 mL/min), ukulungiselelwa kwe-PECM kugcine i-voltage ezinzile kanye namazinga aphezulu e-formic acid FE amahora angu-55 okuhlola ku-200 mA/cm2. Ukuzinza okuphezulu nokukhetha okufinyelelwa yi-catalysts ezitholakala kwezentengiselwano kanye nezinto ze-polymeric membrane kungathuthukiswa ngokuzihlanganisa nama-electrocatalysts alungiselelwe. Umsebenzi olandelayo uzogxila ekulungiseni izimo zokusebenza, ukukhetha kwe-anode catalyst, kanye nesakhiwo se-MEA ukuze kuncishiswe i-formic acid oxidation, okuholela ekungcoleni okugxile kakhulu kuma-voltage aphansi amaseli. Indlela elula yokusebenzisa i-carbon dioxide ye-formic acid evezwe lapha isusa isidingo samakamelo e-anolyte ne-catholyte, izingxenye ze-sandwich, kanye nezinto ezikhethekile, ngaleyo ndlela kwandise ukusebenza kahle kwamandla amaseli futhi kuncishiswe ubunzima besistimu, okwenza kube lula ukukhuliswa. Ukucushwa okuphakanyisiwe kunikeza ipulatifomu yokuthuthukiswa kwesikhathi esizayo kwezitshalo zokuguqula i-CO2 ezisebenza kahle ngokobuchwepheshe nangokwezomnotho.
Ngaphandle kokuthi kushiwo ngenye indlela, zonke izinto ezisetshenziswayo zamakhemikhali kanye nezinyibilikisi zasetshenziswa njengoba zamukelwe. I-Bismuth oxide catalyst (Bi2O3, 80 nm) ithengwe kwa-US Research Nanomaterials, Inc. I-Polymer powder (AP1-CNN8-00-X) inikezwe yi-IONOMR. I-Omnisolv® brand N-propanol (nPA) kanye namanzi acwebezelayo (18.2 Ω, uhlelo lokuhlanza amanzi lwe-Milli–Q® Advantage A10) ithengwe kwa-Millipore Sigma. I-methanol ne-acetone eziqinisekiswe yi-ACS zithengwa kwa-VWR Chemicals BDH® kanye ne-Fisher Chemical, ngokulandelana. I-polymer powder ixutshwe nengxube ye-acetone ne-methanol ngesilinganiso esingu-1:1 ngesisindo ukuze kutholakale i-polymer dispersion enokuqukethwe okungu-6.5 wt.%. Lungisa i-catalytic uyinki ngokuxuba i-20g Bi2O3, amanzi acwebezelayo kakhulu, i-nPA kanye ne-ionomer dispersion ebhodweni elingu-30ml. Ukwakheka kwakuqukethe i-catalyst engu-30 wt.%, isilinganiso sobuningi be-ionomer ne-catalyst esingu-0.02 kanye nesilinganiso sobuningi be-alcohol namanzi esingu-2:3 (40 wt.% nPA). Ngaphambi kokuxuba, kwanezelwa amagremu angu-70 e-Glen Mills 5mm zirconia grinding material. Amasampula abekwa ku-roller yebhodlela ledijithali le-Fisherbrand™ ku-80 rpm amahora angama-26. Vumela i-inki ihlale imizuzu engama-20 ngaphambi kokufaka. I-inki ye-Bi2O3 yafakwa ku-applicator ye-Qualtech automatic (QPI-AFA6800) kusetshenziswa i-1/2″ x 16″ wirewound refill yelabhorethri (RD Specialties - ububanzi obuyi-60 mil) ku-22°C. I-5 mL ye-inki ye-catalytic yafakwa ku-7.5 x 8 inch Sigraacet 39 BB carbon diffusion carrier (fuel cell storage) ngokufaka induku ngesivinini esilinganiselwe esingu-55 mm/sec. Dlulisa lawa ma-electrode amboziwe kuhhavini bese womisa ku-80 °C. Inqubo yokumboza induku kanye nezithombe zemboza ye-GDE ziboniswe ku-Figures S4a kanye no-b. Ithuluzi le-X-ray fluorescence (XRF) (Fischerscope® XDV-SDD, Fischer-Technolgy Inc. USA) liqinisekisile ukuthi umthwalo we-GDE omboziwe wawungu-3.0 mg Bi2O3/cm2.
Ukuze kulungiselelwe ulwelwesi oluhlanganisiwe oluqukethe i-anion exchange membrane (AEM) kanye ne-CEM enezimbobo. I-Nafion NC700 (Chemours, USA) enobukhulu obungu-15 µm yasetshenziswa njengesendlalelo se-CEM. I-anodic catalyst yafuthwa ngqo kwi-FEM ngesilinganiso se-ionomer kuya ku-carbon esingu-0.83 kanye nendawo yokumboza engu-25 cm2. I-platinum esekelwayo enendawo enkulu ebusweni (50 wt.% Pt/C, TEC 10E50E, TANAKA precious metal) enomthwalo ongu-0.25 mg Pt/cm2 yasetshenziswa njenge-anode catalyst. I-Nafion D2020 (Ion Power, USA) yasetshenziswa njenge-inomer yesendlalelo se-anode se-catalyst. Ukubhoboza kwe-CEM kwenziwa ngokusika imigqa ehambisanayo kwifilimu ye-CEM ngezikhawu ezingu-3mm. Imininingwane yenqubo yokubhoboza iboniswe ku-Figures S12b kanye no-c. Kusetshenziswa i-X-ray computed tomography, kwaqinisekiswa ukuthi igebe lokubhoboza lalingu-32.6 μm, njengoba kuboniswe ku-Figure S12d no-e. Ngesikhathi sokuhlanganiswa kweseli, i-membrane ye-CEM enezimbobo eboshwe nge-catalyst yafakwa ephepheni le-Toray elingu-25 cm2 (5 wt% PTFE elashwe, i-Fuel Cell Store, e-USA). I-membrane ye-AEM (PiperION, Versogen, e-USA) enobukhulu obungu-25, 40 noma 80 μm yabekwa phezu kwe-CEM bese kuba ku-GDE cathode. I-membrane ye-AEM yanqunywa yaba yizicucu ezingu-7.5 × 7.5 cm ukuze imboze yonke insimu yokugeleza futhi yacwiliswa ubusuku bonke kusisombululo se-potassium hydroxide esingu-1 M ngaphambi kokuhlanganiswa. Kokubili i-anode ne-cathode zisebenzisa ama-spacer e-PTFE aqinile ngokwanele ukufeza ukucindezelwa kwe-GDE okuhle kakhulu okungu-18%. Imininingwane yenqubo yokuhlanganiswa kwebhethri iboniswe ku-Figure S12a.
Ngesikhathi sokuhlola, iseli elihlanganisiwe lagcinwa ku-60 °C (30, 60, kanye no-80 °C ukuze kufundwe ngokuxhomekeka kokushisa) ngegesi ye-hydrogen engu-0.8 L/min enikezwe i-anode kanye ne-carbon dioxide engu-2 L/min enikezwe i-cathode. Zombili iziteshi zomoya ze-anodic kanye ne-cathodic zafakwa umswakama kumswakama ongu-100% kanye nomfutho we-cathodic ongu-259 kPa. Ngesikhathi sokusebenza, umfudlana wegesi ye-cathode waxutshwa nesisombululo esingu-1 M KOH ngesilinganiso esingu-2 mL/min ukuze kukhuthazwe ukusetshenziswa kombhede we-cathode catalyst kanye nokuhanjiswa kwe-ionic. Hlanganisa umfudlana wegesi ye-anode namanzi acwengekile ngesilinganiso esingu-10 ml/min ukuze kususwe i-formic acid ku-anode. Imininingwane yokufakwa kwedivayisi kanye nemiphumela iboniswe kuMfanekiso S5. Igesi yokukhipha i-cathode iqukethe i-CO2 futhi ikhiqiza i-CO2 kanye ne-H2. Umhwamuko wamanzi ususwa nge-condenser (i-heat exchanger yokushisa ephansi ku-2°C). Igesi esele izoqoqwa ukuze kuhlaziywe isikhathi segesi. Ukugeleza kwe-anode kuzodlula futhi ku-condenser ukuze kuhlukaniswe uketshezi negesi. Amanzi angcolile azoqoqwa ngama-vial ahlanzekile futhi ahlaziywe kusetshenziswa i-chronometry yoketshezi ukuze kulinganiswe i-formic acid ekhiqizwayo. Ukuhlolwa kwe-electrochemical kwenziwe kusetshenziswa i-Garmy potentiostat (inombolo yokubhekisela 30K, Gamry, USA). Ngaphambi kokulinganisa i-polarization curve, iseli lalungiswa izikhathi ezine kusukela ku-0 kuya ku-250 mA/cm2 kusetshenziswa i-linear voltammetry enesilinganiso sokuskena esingu-2.5 mA/cm2. Ama-polarization curve atholwe ngemodi ye-galvanostatic iseli libanjwe ku-current density ethile imizuzu emi-4 ngaphambi kokuthatha isampula yegesi ye-cathode kanye noketshezi lwe-anolyte.
Sisebenzisa i-electrode yokubhekisela ye-hydrogen ku-MEA ukuze sihlukanise i-cathode kanye ne-anodic potentials. Isakhiwo se-electrode yokubhekisela siboniswe ku-Figure S6a. I-membrane ye-Nafion (Nafion 211, IonPower, USA) yasetshenziswa njengebhuloho le-ionic ukuxhuma i-membrane ye-MEA kanye ne-electrode yokubhekisela. Ukuphela komugqa we-Nafion kwaxhunywa ku-electrode yokusabalala kwegesi engu-1 cm2 (GDE) elayishwe i-0.25 mg Pt/cm2 (50 wt% Pt/C, TEC10E50E, TANAKA Precious Metals) efakwe ephepheni le-carbon le-29BC (Fuel Cell Store, USA). ). Ihadiwe ekhethekile ye-polyetherketone (PEEK) isetshenziselwa ukuvala igesi nokuqinisekisa ukuxhumana okuhle phakathi kwe-GDE kanye ne-Nafion strips, nokuxhuma i-electrode yokubhekisela kuhadiwe yeseli likaphethiloli. Ukuphela komugqa we-Nafion kuxhunywe onqenqemeni oluvelayo lwebhethri le-CEM. Isithombe S6b sibonisa ingxenye ephambene ye-electrode yokubhekisela ehlanganiswe ne-MEA.
Ngemva kokuba igesi yokukhipha umoya idlule ku-condenser kanye ne-gas-liquid separator, amasampula egesi athathwa ku-cathode. Igesi eqoqwe yahlaziywa okungenani kathathu kusetshenziswa i-4900 Micro GC (10 μm molecular sieve, Agilent). Amasampula aqoqwe ezikhwameni zesampula zegesi ze-aluminium foil ezinezingqimba eziningi ezingafakwanga i-Supel™ (Sigma-Aldrich) isikhathi esithile (imizuzwana engama-30) futhi afakwa ngesandla ku-microgas chromatograph zingakapheli amahora amabili okuqoqwa. Izinga lokushisa lomjovo labekwa ku-110°C. I-Carbon monoxide (CO) kanye ne-hydrogen (H2) kwahlukaniswa kukholomu ye-MS5A efudumele (105 °C) enengcindezi (28 psi) engu-10 m kusetshenziswa i-argon (Matheson Gas-Matheson Purity) njengegesi ethwalayo. Lokhu kuxhumana kutholwa kusetshenziswa i-Thermal Conductivity Detector (TCD) eyakhelwe ngaphakathi. Ama-GC chromatograms kanye nama-CO kanye nama-H2 calibration curves aboniswe ku-Figure S7. Amasampula e-liquid formic acid aqoqwe kusukela ku-anode isikhathi esithile (imizuzwana eyi-120) futhi ahlungwa kusetshenziswa isihlungi sesirinji se-PTFE esingu-0.22 μm emabhodleleni angu-2 mL. Imikhiqizo ewuketshezi emabhodleleni ihlaziywe kusetshenziswa uhlelo lwe-Agilent 1260 Infinity II bioinert high-performance liquid chromatography (HPLC), lapho kwafakwa khona ama-20 μl esampula nge-autosampler (G5668A) enesigaba esihambayo se-4 mM sulfuric acid (H2SO4). ) ngesilinganiso sokugeleza esingu-0.6 ml/min (ipompo ye-quaternary G5654A). Imikhiqizo yahlukaniswa kuhhavini oshisiwe (35°C, i-column oven G7116A) i-Aminex HPX-87H 300 × 7.8 mm (Bio-Rad) olandelwa yikholomu yokuvikela i-Micro-Guard Cation H. I-Formic acid itholwe kusetshenziswa i-diode array detector (DAD). kubude be-wavelength obungu-210 nm kanye ne-bandwidth engu-4 nm. I-chromatogram ye-HPL kanye ne-formic acid standard calibration curve ziboniswe kuMfanekiso S7.
Imikhiqizo yegesi (i-CO ne-H2) FE ibalwa kusetshenziswa i-equation elandelayo, kanti inani lama-mole egesi libalwa kusetshenziswa i-equation yegesi efanele:
Phakathi kwazo: \({n}_{i}\): inani lama-electron ekusabeleni kwe-electrochemical. \(F\): Okungaguquki kukaFaraday. \({C}_{i}\): Ukuhlushwa komkhiqizo woketshezi lwe-HPLC. \(V\): ivolumu yesampula yoketshezi eqoqwe ngesikhathi esinqunyiwe t. \(j\): ubuningi bamanje. \(A\): Indawo yejiyometri ye-electrode (25 cm2). \(t\): isikhathi sokuhlola. \(P\): ukucindezela okuphelele. \({x}_{i}\): Amaphesenti e-mole yegesi anqunywa yi-GC. \(R\): okungaguquki kwegesi. \(T\): izinga lokushisa.
Ukuhlushwa kwama-anodic cations kwalinganiswa kusetshenziswa i-inductively coupled plasma atomic emission spectroscopy (ICP-OES). Ama-Cations angangena noma asakazeke ku-anode afaka i-Ti, i-Pt, i-Bi kanye ne-K. Ngaphandle kwe-K, wonke amanye ama-cation ayengaphansi komkhawulo wokutholwa. Kwakha ama-ion esixazululweni okushiya i-anode ihambisana nama-proton noma amanye ama-cation. Ngakho-ke, ubumsulwa be-formic acid bungabalwa njengo
Ukukhiqizwa kwe-Formate/FA kumelela inani le-FA elikhiqizwa nge-kWh kagesi elisetshenziswa kusetshenziswa ukucushwa okuthile kwe-MEA, ku-mol/kWh. Kubalwa ngokusekelwe ekuxineni kwamanje, i-voltage yeseli kanye nokusebenza kahle kwe-Faraday ngaphansi kwezimo ezithile zokusebenza.
Bala inani le-formic acid e-oxidized ku-anode ngokusekelwe ebhalansini lesisindo iyonke. Kwenzeka ukusabela okuthathu okuncintisanayo ku-cathode: ukuvela kwe-hydrogen, ukwehla kwe-CO2 kuya ku-CO2, kanye nokwehla kwe-CO2 kuya ku-formic acid. Ngenxa yokuthi sinenqubo yokuxiliswa kwe-formic acid ku-Anton, i-formic acid FE ingahlukaniswa izingxenye ezimbili: ukuqoqwa kwe-formic acid kanye ne-formic acid oxidation. Ibhalansi yesisindo iyonke ingabhalwa kanje:
Sisebenzise i-GC ukuze silinganise inani le-formic acid, i-hydrogen, kanye ne-CO eqoqwe yi-HPLC. Kufanele kuqashelwe ukuthi iningi le-formic acid liqoqwe kusuka ku-anode kusetshenziswa ukusethwa okuboniswe ku-Supplementary Figure S5. Inani le-formate eqoqwe kusuka ekamelweni le-cathode alibalulekile, cishe lingaphansi kwama-oda amabili ngobukhulu, futhi lilingana ngaphansi kuka-0.5% wenani eliphelele le-SC.
Imodeli yokuthutha eqhubekayo esetshenziswe lapha isekelwe emsebenzini wangaphambilini ezinhlelweni ezifanayo34. Uhlelo oluhlanganisiwe lwezibalo ze-Poisson-Nerst-Planck (PNP) lusetshenziselwa ukunquma ukuhlushwa kwamanzi kanye namandla kagesi ezigabeni zokuqhuba ngogesi kanye ne-ionic. Ukubuka konke okuningiliziwe kwezibalo eziyisisekelo kanye ne-geometry yemodeli kunikezwa ku-SI.
Lolu hlelo lunquma ukuhlushwa kwezinto eziyisishiyagalombili zamanzi (\({{{{{\rm{C}}}}}}}{{{{{\rm{O}}}}}}}}_{2 \left ({{{{\rm{aq}}}}}}}\right)}\), \({{{{{\rm{H}}}}}}}}}^{+ }\ ), \ ({{{{\rm{O}}}}}}{{{{{\rm{H}}}}}}^{-}\), \({{{ {{ \rm{HCO}}}}}}}_{3}^{-}\), \({{{{\rm{CO}}}}}}_{3}^{ 2-} \ ),\ ({{{{\rm{HCOOH}}}}}}}\), \({{{{{\rm{HCOO}}}}}}}}}^{- }\) kanye \({{ {{{\rm{K}}}}}}}^{+}\)), amandla kagesi esigabeni sokuqhuba i-ionic (\({\phi }_{I}\ )) kanye nokuqhuba i-electron ye-anodic ne-cathodic. Amandla kagesi kagesi ngezigaba (\({\phi }_{A}\) kanye \({\phi }_{C}\) ngokulandelana). Esikhundleni salokho, imisebenzi yokungathathi hlangothi kagesi yendawo noma yokusabalalisa ishaja ayitholakali, isifunda seshaja sesikhala sixazululwa ngqo kusetshenziswa i-equation kaPoisson; Le ndlela isivumela ukuthi sibonise ngqo imiphumela yokuxosha i-Donnan kuma-interface e-CEM|AEM, CEM|Pore, kanye ne-AEM|Pore. Ngaphezu kwalokho, i-porous electrode theory (PET) isetshenziselwa ukuchaza ukuthuthwa kweshaja ezingqimbeni ze-anodic neze-cathodic ze-catalyst. Ngokwazi kwababhali, lo msebenzi umelela ukusetshenziswa kokuqala kwe-PET ezinhlelweni ezinezindawo eziningi zokushaja isikhala.
Amasampula e-GDE BOT kanye ne-EOT cathode ahlolwe kusetshenziswa i-Zeiss Xradia 800 Ultra enomthombo we-X-ray ongu-8.0 keV, izindlela zokumunca kanye nezindlela zensimu ebanzi, kanye nokuhlanganiswa kwesithombe1. Izithombe ezingu-901 zaqoqwa kusukela ku--90° kuya ku-90° ngesikhathi sokuchayeka semizuzwana engu-50. Ukwakhiwa kabusha kwenziwa kusetshenziswa isihlungi se-back projection esinosayizi we-voxel ongu-64 nm. Ukuhlaziywa kokuhlukaniswa kanye nokusatshalaliswa kosayizi wezinhlayiyana kwenziwa kusetshenziswa ikhodi ebhalwe ngokukhethekile.
Ukuchazwa kwe-electron microscopic kuhilela ukufaka ama-MEA okuhlola ku-epoxy resin ukulungiselela ukuhlukaniswa okuncane kakhulu ngommese wedayimane. Ingxenye ephambene ye-MEA ngayinye yasikwa yaba ugqinsi oluyi-50 kuya ku-75 nm. I-Talos F200X transmission electron microscope (Thermo Fisher Scientific) yasetshenziswa ukuskena i-transmission electron microscopy (STEM) kanye nezilinganiso ze-X-ray spectroscopy (EDS) zamandla. I-microscope ifakwe uhlelo lwe-EDS Super-X olunezitholi ze-SDD ezine ezingenamafasitela futhi lusebenza ku-200 kV.
Amaphethini okusabalalisa i-X-ray ye-Powder (i-PXRD) atholakale ku-Bruker Advance D8 powder X-ray diffractometer ene-Ni-filtered Cu Kα radiation esebenza ku-40 kV kanye ne-40 mA. Ububanzi bokuskena busukela ku-10° kuya ku-60°, usayizi wesinyathelo ungu-0.005°, kanti isivinini sokuthola idatha singumzuzwana owodwa ngesinyathelo.
I-RAS spectrum emaphethelweni e-Bi2O3 Bi L3 catalyst ilinganiswe njengomsebenzi we-potential kusetshenziswa iseli elenziwe ekhaya. Uyinki we-Bi2O3 catalytic ionomer walungiswa kusetshenziswa i-26.1 mg ye-Bi2O3 exutshwe nesisombululo se-ionomer esingu-156.3 μL (6.68%) futhi wancishiswa nge-1 M KOH, amanzi (157 μL) kanye ne-isopropyl alcohol (104 μL) ukuthola i-ionomer. I-catalyst coefficient ingu-0.4. Uyinki wafakwa kumashidi e-graphene ezindaweni eziyisikwele (10×4 mm) kwaze kwaba yilapho umthwalo we-catalyst ye-Bi2O3 ufinyelela ku-0.5 mg/cm2. Ingxenye esele yeshidi le-graphene imbozwe nge-Kapton ukuze kuhlukaniswe lezi zindawo ku-electrolyte. Ishidi le-graphene elimbozwe nge-catalyst lafakwa phakathi kwama-PTFE amabili futhi laboshwa emzimbeni weseli (PEEK) ngezikulufo, Isithombe S8. I-Hg/HgO (1 M NaOH) yasebenza njenge-electrode yokubhekisela, kanti iphepha le-carbon lasebenza njenge-electrode yokuphikisa. I-electrode yokubhekisela ye-Hg/HgO yalinganiswa kusetshenziswa ucingo lweplatinum olucwiliswe ku-hydrogen-saturated 0.1 M KOH ukuguqula wonke amandla alinganisiwe abe yisilinganiso se-hydrogen electrode (RHE). Ama-spectra e-XRD atholwe ngokuqapha amandla e-electrode esebenza ngeshidi le-Bi2O3/graphene ecwiliswe ku-0.1 M KOH, eshiswe ku-30 ​​°C. I-electrolyte ijikeleza ebhethri, lapho i-electrolyte ingena khona phansi kweseli kanye nendawo yokuphuma phezulu ukuqinisekisa ukuthi i-electrolyte ixhumana nesendlalelo se-catalyst lapho kwakheka amabhamuza. I-CH Instruments 760e potentiostat yasetshenziswa ukulawula amandla e-electrode asebenzayo. Uchungechunge lwamandla kwakuyi-open circuit potential: -100, -200, -300, -400, -500, -800, -850, -900, -1000, -1100, -1500 kanye ne-+700 mV kuye nge-RHE. Wonke amandla e-iR alungisiwe.
I-Bi L3 edge (~13424 eV ye-Bi metal) i-X-ray absorption fine structure (XAFS) spectroscopy yenziwe ku-channel 10-ID, Advanced Photon Source (APS), Argonne National Fluorescence Laboratory. I-National Model Measurement Laboratory. I-monochromator ye-Si(111) enamakristalu amabili epholile nge-nitrogen ewuketshezi yasetshenziswa ukulungisa amandla e-X-ray, kwathi isibuko esimbozwe nge-rhodium sasetshenziswa ukunciphisa okuqukethwe kwe-harmonic. Amandla okuskena ahluka kusuka ku-13200 kuya ku-14400 eV, kwathi i-fluorescence yalinganiswa kusetshenziswa i-5 × 5 silicon PIN diode array ngaphandle kwezihlungi noma ama-Soller slits. Amandla okuwela u-zero we-derivative yesibili alinganiswa ku-13271.90 eV ngomphetho we-L2 we-Pt foil. Ngenxa yobukhulu beseli le-electrochemical, kwakungenakwenzeka ukulinganisa ngasikhathi sinye i-spectrum yendinganiso yokubhekisela. Ngakho-ke, ushintsho olubalwe lokuskena ukuze uskene kumandla e-X-ray angengozi luyi-±0.015 eV ngokusekelwe ekulinganisweni okuphindaphindiwe kulo lonke ucwaningo. Ubukhulu besendlalelo se-Bi2O3 buholela ezingeni elithile lokuzimunca kwe-fluorescence; ama-electrode agcina ukuqondiswa okuqondile maqondana nomsebe we-incident kanye ne-detector, okwenza wonke ama-scan afane cishe. I-Near-field XAFS spectrum yasetshenziswa ukunquma isimo se-oxidation kanye nohlobo lwamakhemikhali lwe-bismuth ngokuqhathanisa nesifunda se-XANES sezindinganiso ze-Bi kanye ne-Bi2O3 kusetshenziswa i-algorithm yokuhlanganisa inhlanganisela eqondile yesofthiwe ye-Athena (inguqulo 0.9.26). ngekhodi i-IFEFFIT 44.
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