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Kev txo cov pa roj carbon dioxide mus rau formic acid los ntawm electrochemical yog ib txoj hauv kev zoo los txhim kho kev siv cov pa roj carbon dioxide thiab muaj peev xwm siv tau ua ib qho chaw khaws cia hydrogen. Hauv txoj haujlwm no, ib qho chaw sib dhos electrode membrane xoom-gap tau tsim rau kev tsim cov tshuaj electrochemical ncaj qha ntawm formic acid los ntawm carbon dioxide. Ib qho kev nce qib tseem ceeb ntawm thev naus laus zis yog perforated cation exchange membrane, uas, thaum siv rau hauv kev teeb tsa bipolar membrane, tso cai rau formic acid tsim ntawm lub interface membrane kom raug tshem tawm los ntawm anodic flow field hauv qhov concentration qis li 0.25 M. Tsis muaj cov khoom sib xyaw sandwich ntxiv ntawm anode thiab cathode lub tswv yim tsom mus rau kev siv cov khoom siv roj teeb thiab cov qauv tsim uas twb muaj lawm hauv cov roj teeb thiab hydrogen electrolysis, tso cai rau kev hloov pauv sai dua mus rau kev nce qib thiab kev lag luam. Hauv lub cell 25 cm2, qhov kev teeb tsa perforated cation exchange membrane muab >75% Faraday efficiency rau formic acid ntawm <2 V thiab 300 mA / cm2. Qhov tseem ceeb tshaj, kev sim ruaj khov 55-teev ntawm 200 mA / cm2 tau qhia txog Faraday efficiency ruaj khov thiab lub zog hluav taws xob ntawm lub cell. Kev tshuaj xyuas thev naus laus zis thiab kev lag luam yog siv los piav qhia txog cov hau kev los ua kom tau txais kev sib npaug ntawm tus nqi nrog cov txheej txheem tsim cov kua qaub formic tam sim no.
Kev txo cov pa roj carbon dioxide mus rau formic acid siv hluav taws xob rov ua dua tshiab tau pom tias txo cov nqi tsim khoom txog li 75%1 piv rau cov txheej txheem roj fossil ib txwm muaj. Raws li tau qhia hauv cov ntaub ntawv2,3, formic acid muaj ntau yam kev siv, los ntawm txoj hauv kev zoo thiab pheej yig ntawm kev khaws cia thiab thauj hydrogen mus rau cov khoom noj rau kev lag luam tshuaj4,5 lossis kev lag luam biomass6. Formic acid txawm tias tau txheeb xyuas tias yog cov khoom noj rau kev hloov pauv tom qab mus rau hauv cov roj dav hlau ruaj khov siv cov txheej txheem metabolic7,8. Nrog rau kev txhim kho ntawm formic acid economics1,9, ntau txoj haujlwm tshawb fawb tau tsom mus rau kev ua kom zoo dua catalyst selectivity10,11,12,13,14,15,16. Txawm li cas los xij, ntau yam kev siv zog txuas ntxiv tsom mus rau cov H-cell me me lossis cov kua dej ntws ua haujlwm ntawm qhov ceev tam sim no qis (<50 mA/cm2). Yuav kom txo tau cov nqi, ua tiav kev lag luam thiab nce kev nkag mus rau hauv kev lag luam tom qab, kev txo cov pa roj carbon dioxide electrochemical (CO2R) yuav tsum tau ua ntawm qhov siab tam sim no (≥200 mA / cm2) thiab Faraday efficiency (FE)17 thaum siv cov khoom siv ntau tshaj plaws thiab siv cov khoom siv roj teeb los ntawm cov roj teeb thev naus laus zis thiab dej electrolysis tso cai rau CO2R cov khoom siv kom tau txais txiaj ntsig ntawm kev lag luam ntawm qhov ntsuas18. Tsis tas li ntawd, txhawm rau kom nce qhov siv tau ntawm kev tsim khoom thiab zam kev ua tiav ntxiv, formic acid yuav tsum tau siv ua cov khoom kawg es tsis yog formate salts19.
Hauv qhov kev taw qhia no, tsis ntev los no tau muaj kev siv zog los tsim cov khoom siv CO2R formate/formic acid raws li roj diffusion electrode (GDE) uas tsim nyog rau kev lag luam. Kev tshuaj xyuas tag nrho los ntawm Fernandez-Caso et al.20 sau txhua qhov kev teeb tsa electrochemical cell rau kev txo qis CO2 mus rau formic acid/formate. Feem ntau, txhua qhov kev teeb tsa uas twb muaj lawm tuaj yeem muab faib ua peb pawg tseem ceeb: 1. Cov catholytes ntws-dhau19,21,22,23,24,25,26,27, 2. Ib daim nyias nyias (cation pauv daim nyias nyias (CEM)28 lossis anion pauv daim nyias nyias (AEM)29 thiab 3. Sandwich configuration15,30,31,32. Cov ntu yooj yim ntawm cov kev teeb tsa no tau qhia hauv Daim Duab 1a. Rau qhov kev teeb tsa ntws ntawm catholyte, lub chamber electrolyte tau tsim ntawm daim nyias nyias thiab cathode ntawm GDE. Flow-through catholyte yog siv los tsim cov ion channels hauv cathode txheej ntawm catalyst33, txawm hais tias nws qhov xav tau rau kev tswj hwm format selectivity yog debated34. Txawm li cas los xij, qhov kev teeb tsa no tau siv los ntawm Chen et al. Siv SnO2 cathode ntawm cov pa roj carbon substrate nrog 1.27 hli tuab catholyte txheej, txog li 90% FE 35 ntawm 500 mA / cm2 tau ua tiav. Kev sib xyaw ua ke ntawm cov txheej catholyte tuab thiab a Daim nyias nyias bipolar rov qab (BPM) uas txwv kev hloov pauv ion muab lub zog ua haujlwm ntawm 6 V thiab kev siv hluav taws xob zoo ntawm 15%. Txhawm rau txhim kho kev siv hluav taws xob zoo, Li et al., siv ib qho CEM configuration, tau ua tiav FE 29 ntawm 93.3% ntawm qhov ceev tam sim no ntawm 51.7 mA / cm2. Diaz-Sainz et al.28 siv lub tshuab lim dej nrog ib daim nyias nyias CEM ntawm qhov ceev tam sim no ntawm 45 mA / cm2. Txawm li cas los xij, txhua txoj kev tsim tawm format es tsis yog cov khoom nyiam, formic acid. Ntxiv rau cov kev xav tau ua tiav ntxiv, hauv CEM configurations, cov hom ntawv xws li KCOOH tuaj yeem sib sau ua ke sai sai hauv GDE thiab thaj chaw ntws, ua rau muaj kev txwv kev thauj mus los thiab thaum kawg ua tsis tiav ntawm tes.
Kev sib piv ntawm peb qhov tseem ceeb tshaj plaws CO2R rau formate/formic acid hloov pauv khoom siv teeb tsa thiab cov qauv tsim uas tau thov hauv kev tshawb fawb no. b Kev sib piv ntawm tag nrho cov tam sim no thiab formate/formic acid cov zis rau catholyte teeb tsa, sandwich teeb tsa, ib qho CEM teeb tsa hauv cov ntaub ntawv (qhia hauv Supplementary Table S1) thiab peb txoj haujlwm. Cov cim qhib qhia txog kev tsim cov tshuaj formate, thiab cov cim khov kho qhia txog kev tsim cov kua formic acid. * Kev teeb tsa qhia siv hydrogen ntawm anode. c Zero-gap MEA teeb tsa siv lub membrane bipolar sib xyaw nrog lub perforated cation pauv txheej ua haujlwm hauv hom kev sib tsoo pem hauv ntej.
Txhawm rau tiv thaiv kev tsim cov qauv, Proietto et al. 32 siv lub tshuab lim dej sib cais uas cov dej deionized ntws los ntawm cov txheej nruab nrab. Lub kaw lus tuaj yeem ua tiav >70% CE hauv qhov ceev tam sim no ntawm 50–80 mA / cm2. Ib yam li ntawd, Yang et al. 14 tau tawm tswv yim siv cov khoom siv electrolyte interlayer ntawm CEM thiab AEM los txhawb kev tsim cov kua qaub formic. Yang et al.31,36 tau ua tiav 91.3% FE hauv lub cell 5 cm2 ntawm 200 mA / cm2, tsim cov kua qaub formic 6.35 wt%. Xia et al. Siv cov qauv zoo sib xws, 83% kev hloov pauv ntawm carbon dioxide (CO2) rau formic acid FE tau ua tiav ntawm 200 mA / cm2, thiab lub zog ntawm lub kaw lus tau sim rau 100 teev 30 feeb. Txawm hais tias cov txiaj ntsig me me muaj kev cia siab, qhov nce nqi thiab qhov nyuaj ntawm cov porous ion pauv resins ua rau nws nyuaj rau kev teeb tsa interlayer rau cov kab ke loj dua (piv txwv li, 1000 cm2).
Yuav kom pom tau qhov cuam tshuam ntawm cov qauv tsim sib txawv, peb tau teev cov qauv tsim / formic acid ib kWh rau txhua lub kaw lus uas tau hais ua ntej thiab tau kos duab rau hauv Daim Duab 1b. Nws yog qhov tseeb ntawm no tias txhua lub kaw lus uas muaj catholyte lossis interlayer yuav ua rau nws qhov kev ua tau zoo tshaj plaws ntawm qhov ceev tam sim no qis thiab poob qis ntawm qhov ceev tam sim no siab dua, qhov twg qhov txwv ohmic yuav txiav txim siab qhov hluav taws xob ntawm tes. Ntxiv mus, txawm hais tias qhov kev teeb tsa CEM txuag hluav taws xob muab qhov siab tshaj plaws ntawm cov kua qaub formic acid ib kWh, kev tsim ntsev tuaj yeem ua rau muaj kev puas tsuaj sai ntawm qhov ceev tam sim no siab.
Txhawm rau kom txo qhov kev ua tsis tiav uas tau tham ua ntej, peb tau tsim ib lub membrane electrode assembly (MEA) uas muaj ib qho composite forward biased BPM nrog ib lub perforated cation exchange membrane (PCEM). Lub architecture tau qhia nyob rau hauv Daim Duab 1c. Hydrogen (H2) raug nkag mus rau hauv lub anode los tsim cov protons los ntawm kev ua hydrogen oxidation reaction (HOR). Ib txheej PCEM raug nkag mus rau hauv BPM system kom tso cai rau formate ions tsim ntawm cathode hla dhau AEM, sib xyaw nrog protons los tsim cov formic acid ntawm BPM interface thiab interstitial pores ntawm CEM, thiab tom qab ntawd tawm los ntawm GDE anode thiab flow field. . Siv qhov kev teeb tsa no, peb tau ua tiav >75% FE ntawm formic acid ntawm <2 V thiab 300 mA/cm2 rau thaj chaw cell 25 cm2. Qhov tseem ceeb tshaj plaws, tus qauv tsim siv cov khoom lag luam thiab cov khoom siv kho vajtse rau cov roj cell thiab cov dej electrolysis cog, uas ua rau lub sijhawm sai dua los ntsuas. Catholyte configurations muaj catholyte flow chambers uas tuaj yeem ua rau muaj kev tsis sib npaug ntawm cov roj thiab cov kua theem, tshwj xeeb tshaj yog nyob rau hauv cov cell loj dua. Rau cov qauv sandwich nrog cov txheej porous ntawm cov kua dej ntws, yuav tsum muaj kev siv zog ntau los ua kom zoo dua cov txheej porous intermediate kom txo qhov siab poob thiab cov pa roj carbon dioxide sib sau ua ke hauv cov txheej nruab nrab. Ob qho no tuaj yeem ua rau muaj kev cuam tshuam ntawm kev sib txuas lus ntawm tes. Nws kuj nyuaj rau tsim cov txheej nyias nyias sawv ntsug ntawm qhov loj. Qhov sib txawv, qhov kev teeb tsa tshiab uas tau thov yog qhov kev teeb tsa MEA xoom-gap uas tsis muaj chav ntws lossis txheej nruab nrab. Piv rau lwm cov hlwb electrochemical uas twb muaj lawm, qhov kev teeb tsa uas tau thov yog qhov tshwj xeeb hauv qhov nws tso cai rau kev tsim cov kua qaub formic ncaj qha hauv qhov scalable, txuag hluav taws xob, xoom-gap configuration.
Txhawm rau kom tsis txhob muaj kev hloov pauv hydrogen, kev siv zog txo CO2 loj tau siv MEA thiab AEM membrane configurations ua ke nrog cov electrolytes siab molar concentration (piv txwv li, 1-10 M KOH) los tsim cov xwm txheej alkaline ntawm cathode (raws li pom hauv Daim Duab 2a). Hauv cov kev teeb tsa no, formate ions tsim ntawm cathode dhau los ntawm daim nyias nyias ua cov hom tsis zoo, tom qab ntawd KCOOH raug tsim thiab tawm hauv lub kaw lus los ntawm cov kwj deg anodic KOH. Txawm hais tias formate FE thiab cell voltage tau pib zoo raws li pom hauv Daim Duab 2b, kev sim ruaj khov ua rau FE txo qis kwv yees li 30% hauv 10 teev xwb (Daim Duab S1a-c). Nws yuav tsum tau sau tseg tias kev siv 1 M KOH anolyte yog qhov tseem ceeb los txo qis anodic overvoltage hauv alkaline oxygen evolution reaction (OER) systems37 thiab ua tiav ion accessibility hauv cathode catalyst txaj33. Thaum qhov concentration ntawm anolyte raug txo kom txog 0.1 M KOH, ob qho tib si lub zog ntawm lub cell thiab formic acid oxidation (kev poob ntawm formic acid) nce ntxiv (Daim Duab S1d), qhia txog kev lag luam xoom-sum. Qib ntawm formate oxidation tau soj ntsuam siv qhov sib npaug ntawm qhov hnyav tag nrho; kom paub meej ntxiv, saib ntu "Txoj Kev". Kev ua tau zoo siv MEA thiab ib qho CEM membrane configurations kuj tau kawm, thiab cov txiaj ntsig tau pom hauv Daim Duab S1f, g. FE formate sau los ntawm cathode yog> 60% ntawm 200 mA / cm2 thaum pib ntawm qhov kev xeem, tab sis sai sai degraded hauv ob teev vim yog cathode ntsev accumulation uas tau tham ua ntej (Daim Duab S11).
Daim duab qhia txog MEA uas tsis muaj qhov sib txawv nrog CO2R ntawm cathode, hydrogen oxidation reaction (HOR) lossis OER ntawm anode, thiab ib daim AEM membrane nyob nruab nrab. b FE thiab cell voltage rau qhov kev teeb tsa no nrog 1 M KOH thiab OER ntws ntawm anode. Cov kab yuam kev sawv cev rau qhov kev hloov pauv tus qauv ntawm peb qhov kev ntsuas sib txawv. hauv FE thiab lub zog ntawm lub cev nrog H2 thiab HOR ntawm anode. Cov xim sib txawv yog siv los paub qhov txawv ntawm formate thiab formic acid tsim. d Daim duab qhia txog MEA nrog BPM txav mus rau pem hauv ntej hauv nruab nrab. FE thiab roj teeb voltage piv rau lub sijhawm ntawm 200 mA / cm2 siv qhov kev teeb tsa no. f Daim duab hla-sectional ntawm BPM MEA tom qab kev sim luv luv.
Yuav kom tsim tau cov kua qaub formic, hydrogen raug muab rau Pt-on-carbon (Pt/C) catalyst ntawm lub anode. Raws li pom hauv Daim Duab 2d, ib qho protons tsim BPM pem hauv ntej ntawm lub anode tau raug tshawb nrhiav ua ntej kom ua tiav kev tsim cov kua qaub formic. Lub tshuab kho BPM tsis ua haujlwm tom qab 40 feeb ntawm kev ua haujlwm ntawm qhov tam sim no ntawm 200 mA / cm2, nrog rau qhov hluav taws xob ntau dua 5 V (Daim Duab 2e). Tom qab sim, pom tseeb delamination tau pom ntawm CEM/AEM interface. Dhau li ntawm formate, anions xws li carbonate, bicarbonate thiab hydroxide kuj tuaj yeem hla dhau AEM membrane thiab cuam tshuam nrog protons ntawm CEM/AEM interface los tsim cov roj CO2 thiab dej kua, ua rau BPM delamination (Daim Duab 2f) thiab, thaum kawg ua rau lub cell tsis ua haujlwm.
Raws li kev ua tau zoo thiab cov txheej txheem ua tsis tiav ntawm cov qauv saum toj no, ib qho MEA architecture tshiab tau raug pom zoo raws li pom hauv Daim Duab 1c thiab piav qhia hauv Daim Duab 3a38. Ntawm no, PCEM txheej muab txoj hauv kev rau kev tsiv teb tsaws chaw ntawm formic acid thiab anions los ntawm CEM / AEM interface, yog li txo qhov kev sib sau ua ke ntawm cov tshuaj. Tib lub sijhawm, PCEM interstitial txoj kev coj formic acid mus rau hauv qhov nruab nrab diffusion thiab flow field, txo qhov ua tau ntawm formic acid oxidation. Cov txiaj ntsig polarization siv AEMs nrog thicknesses ntawm 80, 40 thiab 25 mm tau pom hauv Daim Duab 3b. Raws li xav tau, txawm hais tias tag nrho cov cell voltage nce nrog kev nce AEM thickness, siv cov AEM tuab dua tiv thaiv rov qab diffusion ntawm formic acid, yog li ua rau cathode pH nce thiab txo H2 ntau lawm (Daim Duab 3c-e).
a Daim duab ntawm MEA qauv nrog AEM thiab perforated CEM thiab cov kev thauj mus los ntawm cov kua qaub formic sib txawv. b Lub zog hluav taws xob ntawm cov hluav taws xob sib txawv thiab cov tuab AEM sib txawv. hauv EE ntawm ntau qhov hluav taws xob sib txawv nrog AEM tuab ntawm 80 μm (d) 40 μm, e) 25 μm. Cov kab yuam kev sawv cev rau qhov kev hloov pauv tus qauv ntsuas los ntawm peb qhov qauv sib cais. f Cov txiaj ntsig simulation ntawm cov kua qaub formic concentration thiab tus nqi pH ntawm CEM/AEM interface ntawm cov tuab AEM sib txawv. f PC thiab pH hauv txheej cathode ntawm cov catalyst nrog cov tuab zaj duab xis AEM sib txawv. g Kev faib tawm ob-seem ntawm cov kua qaub formic concentration nrog CEM/AEM interface thiab perforation.
Daim Duab S2 qhia txog kev faib tawm ntawm cov kua qaub formic acid thiab pH thoob plaws MEA tuab siv Poisson-Nernst-Planck finite element modeling. Nws tsis yog qhov xav tsis thoob tias qhov concentration siab tshaj plaws ntawm cov kua qaub formic, 0.23 mol / L, tau pom ntawm CEM / AEM interface, txij li cov kua qaub formic tau tsim ntawm qhov interface no. Qhov concentration ntawm cov kua qaub formic los ntawm AEM txo qis sai dua thaum qhov tuab ntawm AEM nce ntxiv, qhia txog kev tiv thaiv ntau dua rau kev hloov pauv loj thiab tsawg dua cov kua qaub formic acid flux vim yog rov qab diffusion. Daim Duab 3 f thiab g qhia txog pH thiab cov nqi formic acid hauv lub txaj cathode catalyst los ntawm kev rov qab diffusion thiab ob-seem faib ntawm cov kua qaub formic acid concentration, feem. Qhov nyias dua ntawm AEM membrane, qhov siab dua qhov concentration ntawm cov kua qaub formic acid ze ntawm cathode, thiab pH ntawm cathode dhau los ua acidic. Yog li ntawd, txawm hais tias cov kua qaub AEM tuab dua ua rau muaj kev poob ohmic ntau dua, lawv tseem ceeb heev rau kev tiv thaiv kev rov qab diffusion ntawm cov kua qaub formic acid mus rau cathode thiab ua kom muaj kev ntshiab siab ntawm FE formic acid system. Thaum kawg, kev nce AEM tuab mus rau 80 μm ua rau FE > 75% rau formic acid ntawm <2 V thiab 300 mA / cm2 rau thaj tsam cell 25 cm2.
Txhawm rau sim qhov ruaj khov ntawm cov qauv PECM-raws li no, lub roj teeb tam sim no tau khaws cia ntawm 200 mA / cm2 rau 55 teev. Cov txiaj ntsig tag nrho tau pom hauv Daim Duab 4, nrog rau cov txiaj ntsig los ntawm 3 teev thawj zaug tau hais meej hauv Daim Duab S3. Thaum siv Pt / C anodic catalyst, lub zog ntawm lub cell tau nce siab heev hauv thawj 30 feeb (Daim Duab S3a). Dhau lub sijhawm ntev dua, lub zog ntawm lub cell tseem yuav luag tas li, muab qhov kev puas tsuaj ntawm 0.6 mV / h (Daim Duab 4a). Thaum pib ntawm qhov kev sim, PV ntawm formic acid sau ntawm anode yog 76.5% thiab PV ntawm hydrogen sau ntawm cathode yog 19.2%. Tom qab thawj teev ntawm kev sim, hydrogen FE poob qis mus rau 13.8%, qhia txog kev xaiv format zoo dua. Txawm li cas los xij, tus nqi oxidation ntawm formic acid hauv lub cev poob qis mus rau 62.7% hauv 1 teev, thiab tus nqi oxidation ntawm anodic formic acid nce ntxiv los ntawm yuav luag xoom thaum pib ntawm qhov kev sim mus rau 17.0%. Tom qab ntawd, FE ntawm H2, CO, formic acid thiab tus nqi ntawm anodic oxidation ntawm formic acid tseem ruaj khov thaum lub sijhawm sim. Qhov nce ntawm formic acid oxidation thaum thawj teev yuav yog vim muaj kev sib sau ua ke ntawm formic acid ntawm PCEM/AEM interface. Thaum qhov concentration ntawm formic acid nce ntxiv, nws tsis yog tsuas yog tawm los ntawm qhov perforation ntawm daim nyias nyias, tab sis kuj diffuses los ntawm FEM nws tus kheej thiab nkag mus rau hauv Pt/C anode txheej. Txij li thaum formic acid yog kua ntawm 60 ° C, nws cov kev sib sau ua ke tuaj yeem ua rau muaj teeb meem hloov pauv huab hwm coj thiab ua rau muaj kev nyiam oxidation dua li hydrogen.
a Lub zog ntawm lub cell piv rau lub sijhawm (200 mA/cm2, 60 °C). Daim duab ntxig qhia txog daim duab microscope ntawm qhov seem ntawm MEA nrog lub perforated EM. Scale bar: 300 µm. b Purity ntawm PE thiab formic acid ua haujlwm ntawm lub sijhawm ntawm 200 mA/cm2 siv Pt/C anode.
Cov qauv ntawm cov qauv thaum pib sim (BOT) thaum lub sijhawm npaj thiab thaum kawg ntawm kev sim (EOT) tom qab 55 teev ntawm kev sim ruaj khov tau piav qhia siv nano-X-ray computed tomography (nano-CT), raws li pom hauv Daim Duab 5 a. Cov qauv EOT muaj qhov loj dua ntawm cov khoom catalyst nrog lub cheeb ntawm 1207 nm piv rau 930 nm rau BOT. Cov duab high-angle annular dark-field scanning electron microscopy (HAADF-STEM) thiab cov txiaj ntsig ntawm lub zog-dispersive X-ray spectroscopy (EDS) tau pom hauv Daim Duab 5b. Thaum lub txheej catalyst BOT muaj feem ntau ntawm cov khoom me me catalyst nrog rau qee cov agglomerates loj dua, nyob rau theem EOT lub txheej catalyst tuaj yeem faib ua ob thaj chaw sib txawv: ib qho nrog cov khoom khov loj dua thiab lwm qhov nrog cov cheeb tsam porous ntau dua. Tus naj npawb ntawm cov khoom me me. Daim duab EDS qhia tau hais tias cov khoom khov loj muaj ntau hauv Bi, tej zaum yog hlau Bi, thiab cov cheeb tsam porous muaj ntau hauv oxygen. Thaum lub cell ua haujlwm ntawm 200 mA / cm2, lub peev xwm tsis zoo ntawm cathode yuav ua rau Bi2O3 txo qis, raws li pov thawj los ntawm cov txiaj ntsig in situ X-ray absorption spectroscopy uas tau tham hauv qab no. HAADF-STEM thiab EDS mapping cov txiaj ntsig qhia tau tias Bi2O3 dhau los ntawm cov txheej txheem txo qis, ua rau lawv poob oxygen thiab agglomerate rau hauv cov hlau loj dua. Cov qauv X-ray diffraction ntawm BOT thiab EOT cathodes lees paub qhov kev txhais lus ntawm cov ntaub ntawv EDS (Daim duab 5c): tsuas yog crystalline Bi2O3 tau pom hauv BOT cathode, thiab crystalline bimetal tau pom hauv EOT cathode. Txhawm rau nkag siab txog qhov cuam tshuam ntawm cathode peev xwm ntawm lub xeev oxidation ntawm Bi2O3 cathode catalyst, qhov kub tau hloov pauv los ntawm qhib circuit peev xwm (+0.3 V vs RHE) mus rau -1.5 V (vs RHE). Nws tau pom tias theem Bi2O3 pib txo qis ntawm -0.85 V piv rau RHE, thiab qhov txo qis ntawm qhov muaj zog ntawm kab dawb hauv thaj tsam ntug ntawm lub spectrum qhia tias cov hlau Bi raug txo qis rau 90% ntawm RHE ntawm -1.1 V tawm tsam RHE (Daim duab 5d). Txawm hais tias lub tshuab ua haujlwm li cas los xij, qhov kev xaiv tag nrho ntawm formate ntawm cathode yeej tsis hloov pauv, raws li tau txiav txim siab los ntawm H2 thiab CO FE thiab formic acid tsim, txawm tias muaj kev hloov pauv tseem ceeb hauv cathode morphology, catalyst oxidation xeev, thiab microcrystalline qauv.
a Cov qauv peb-seem ntawm cov txheej catalyst thiab kev faib tawm ntawm cov khoom catalyst tau txais los ntawm kev siv nano-X-ray CT. Scale bar: 10 µm. b Sab saum toj 2: Cov duab HAADF-STEM ntawm cov txheej cathode ntawm BOT thiab EOT catalysts. Scale bar: 1 µm. Hauv qab 2: Cov duab HADF-STEM thiab EDX loj dua ntawm cov txheej cathode ntawm EOT catalyst. Scale bar: 100 nm. c Cov qauv X-ray diffraction ntawm BOT thiab EOT cathode qauv. d Hauv situ X-ray absorption spectra ntawm Bi2O3 electrode hauv 0.1 M KOH ua haujlwm ntawm lub peev xwm (0.8 V txog -1.5 V vs. RHE).
Txhawm rau txiav txim siab seb muaj lub cib fim dab tsi rau kev txhim kho kev siv hluav taws xob zoo los ntawm kev txwv tsis pub formic acid oxidation, H2 reference electrode tau siv los txheeb xyuas qhov kev koom tes ntawm qhov poob hluav taws xob 39. Ntawm qhov tam sim no tsawg dua 500 mA / cm2, lub peev xwm cathode tseem nyob hauv qab -1.25 V. Lub peev xwm anodic tau muab faib ua ob ntu tseem ceeb: qhov sib pauv tam sim no HOR thiab qhov theoretical overvoltage HOR 40 kwv yees los ntawm qhov ntsuas Bulter-Volmer equation ua ntej, thiab qhov seem yog vim oxidation formic acid. Vim yog qhov qeeb dua ntawm cov tshuaj tiv thaiv kinetics piv rau HOR41, qhov me me ntawm formic acid oxidation reaction ntawm anode tuaj yeem ua rau muaj kev nce ntxiv ntawm lub peev xwm anodic. Cov txiaj ntsig qhia tau tias kev txwv tsis pub tag nrho ntawm formic acid anodic oxidation tuaj yeem tshem tawm yuav luag 500 mV overvoltage.
Txhawm rau sim qhov kev kwv yees no, qhov ntws ntawm cov dej deionized (DI) ntawm qhov anode inlet tau hloov pauv kom txo qhov concentration ntawm effluent formic acid. Cov duab 6b thiab c qhia FE, formic acid concentration, thiab cell voltage ua haujlwm ntawm DI flux ntawm anode ntawm 200 mA / cm2. Raws li qhov ntws ntawm cov dej deionized nce ntxiv los ntawm 3.3 mL / feeb mus rau 25 mL / feeb, qhov formic acid concentration ntawm anode txo qis los ntawm 0.27 mol / L mus rau 0.08 mol / L. Piv txwv li, siv cov qauv sandwich uas tau hais los ntawm Xia et al. 30 qhov formic acid concentration ntawm 1.8 mol / L tau txais ntawm 200 mA / cm2. Kev txo qis qhov concentration txhim kho tag nrho FE ntawm formic acid thiab txo qis FE ntawm H2 thaum cathode pH dhau los ua alkaline ntau dua vim yog qhov txo qis rov qab diffusion ntawm formic acid. Qhov txo qis ntawm cov kua qaub formic acid ntawm qhov siab tshaj plaws DI ntws kuj tseem tshem tawm cov kua qaub formic oxidation, ua rau tag nrho cov hluav taws xob ntawm lub cell tsuas yog qis dua 1.7 V ntawm 200 mA / cm2. Qhov kub ntawm lub roj teeb kuj cuam tshuam rau kev ua haujlwm tag nrho, thiab cov txiaj ntsig tau pom hauv Daim Duab S10. Txawm li cas los xij, PCEM-raws li architectures tuaj yeem txhim kho kev siv hluav taws xob zoo hauv kev tiv thaiv cov kua qaub formic oxidation, txawm tias los ntawm kev siv cov catalysts anodic nrog kev xaiv hydrogen zoo dua rau cov kua qaub formic lossis los ntawm kev ua haujlwm ntawm lub cuab yeej.
a Kev rhuav tshem lub zog hluav taws xob ntawm lub cell siv lub cell reference H2 electrode ua haujlwm ntawm 60 °C, Pt/C anode thiab 80 µm AEM. b FE thiab formic acid concentrations sau ntawm 200 mA/cm2 siv cov nqi ntws sib txawv ntawm cov dej anodic deionized. c Thaum lub anode sau cov formic acid hauv cov concentrations sib txawv, lub zog hluav taws xob ntawm lub cell yog 200 mA/cm2. Cov kab yuam kev sawv cev rau qhov kev hloov pauv tus qauv ntawm peb qhov kev ntsuas sib txawv. d Tus nqi muag tsawg kawg nkaus faib los ntawm kev ua tau zoo ntawm ntau tus nqi ntws dej deionized siv cov nqi hluav taws xob nruab nrab hauv tebchaws ntawm US $ 0.068 / kWh thiab US $ 4.5 / kg hydrogen. (*: Lub xeev oxidation tsawg kawg nkaus ntawm formic acid ntawm lub anode yog xav tias yog 10 M FA, tus nqi hluav taws xob nruab nrab hauv tebchaws yog $ 0.068 / kWh, thiab hydrogen yog $ 4.5 / kg. **: Lub xeev oxidation tsawg kawg nkaus yog xav tias yog formic acid. Qhov concentration ntawm FA ntawm lub anode yog 1.3 M anode, tus nqi hluav taws xob yav tom ntej xav tau yog $ 0.03 / kWh, thiab kab dotted sawv cev rau tus nqi lag luam ntawm 85 wt% FA.
Ib qho kev tshuaj xyuas kev lag luam thev naus laus zis (TEA) tau ua tiav kom tau txais tus nqi muag tsawg kawg nkaus ntawm cov roj sib dhos hauv ntau yam kev ua haujlwm, raws li pom hauv Daim Duab 5d. Cov txheej txheem thiab cov ntaub ntawv keeb kwm yav dhau los rau TEA tuaj yeem pom hauv SI. Thaum qhov LC concentration hauv qhov anode pa tawm siab dua, txawm tias qhov hluav taws xob ntawm lub cell siab dua, tag nrho tus nqi ntawm cov roj sib dhos raug txo vim yog qhov txo qis ntawm kev sib cais. Yog tias anodic oxidation ntawm formic acid tuaj yeem txo qis los ntawm kev tsim catalyst lossis electrode technology, kev sib xyaw ua ke ntawm qhov hluav taws xob qis dua (1.66 V) thiab qhov siab dua FA concentration hauv effluent (10 M) yuav txo tus nqi ntawm electrochemical FA ntau lawm rau 0.74 US dollars / kg (raws li hluav taws xob). tus nqi) $ 0.068 / kWh thiab $ 4.5 / kg hydrogen42. Ntxiv mus, thaum ua ke nrog tus nqi kwv yees yav tom ntej ntawm hluav taws xob rov ua dua tshiab ntawm $ 0.03 / kWh thiab hydrogen ntawm $ 2.3 / kg, lub hom phiaj FA wastewater raug txo kom 1.3 lab, ua rau tus nqi tsim khoom kawg kwv yees yog US $ 0.66 / kg43. Qhov no piv rau tus nqi lag luam tam sim no. Yog li, kev siv zog yav tom ntej uas tsom mus rau cov khoom siv hluav taws xob thiab cov qauv tuaj yeem txo qhov anodization ntxiv thaum tso cai rau kev ua haujlwm ntawm cov hluav taws xob qis dua los tsim cov LC concentration siab dua.
Hauv kev xaus, peb tau kawm ntau qhov qauv MEA xoom-qhov sib txawv rau kev txo CO2 rau formic acid thiab tau tawm tswv yim rau cov qauv uas muaj cov txheej txheem sib xyaw ua ke nrog cov txheej txheem pauv pauv perforated cation (PECM) los pab txhawb cov txheej txheem hloov pauv rau cov kua qaub formic. . Cov qauv no tsim > 96% formic acid ntawm cov concentration txog li 0.25 M (ntawm tus nqi ntws anode DI ntawm 3.3 mL / min). Ntawm cov nqi ntws DI siab dua (25 mL / min), cov qauv no muab qhov ceev tam sim no ntawm > 80% FE ntawm 200 mA / cm2 ntawm 1.7 V siv thaj chaw cell 25 cm2. Ntawm cov nqi anodic DI nruab nrab (10 mL / min), PECM configuration tswj hwm qhov hluav taws xob ruaj khov thiab cov qib formic acid FE siab rau 55 teev ntawm kev sim ntawm 200 mA / cm2. Qhov ruaj khov siab thiab kev xaiv ua tiav los ntawm cov catalysts muaj nyob hauv khw thiab cov ntaub ntawv polymeric membrane tuaj yeem txhim kho ntxiv los ntawm kev sib xyaw ua ke nrog cov electrocatalysts zoo tshaj plaws. Cov haujlwm tom ntej yuav tsom mus rau kev kho cov xwm txheej ua haujlwm, kev xaiv catalyst anode, thiab MEA qauv los txo cov formic acid oxidation, ua rau muaj cov dej khib nyiab ntau dua ntawm cov hluav taws xob qis dua. Txoj hauv kev yooj yim rau kev siv carbon dioxide rau formic acid uas tau nthuav tawm ntawm no tshem tawm qhov xav tau rau anolyte thiab catholyte chambers, sandwich Cheebtsam, thiab cov ntaub ntawv tshwj xeeb, yog li ua rau lub zog ntawm lub cell ua haujlwm tau zoo dua thiab txo qhov nyuaj ntawm lub kaw lus, ua rau nws yooj yim dua rau kev nthuav dav. Qhov kev teeb tsa uas tau thov muab lub platform rau kev txhim kho yav tom ntej ntawm cov nroj tsuag hloov pauv CO2 uas muaj peev xwm thiab kev lag luam.
Tshwj tsis yog hais lwm yam, txhua yam khoom siv tshuaj lom neeg thiab cov kuab tshuaj tau siv raws li tau txais. Bismuth oxide catalyst (Bi2O3, 80 nm) tau yuav los ntawm US Research Nanomaterials, Inc. Polymer hmoov (AP1-CNN8-00-X) tau muab los ntawm IONOMR. Omnisolv® hom N-propanol (nPA) thiab ultrapure dej (18.2 Ω, Milli-Q® Advantage A10 dej purification system) tau yuav los ntawm Millipore Sigma. ACS certified methanol thiab acetone tau yuav los ntawm VWR Chemicals BDH® thiab Fisher Chemical, feem. Cov hmoov polymer tau sib xyaw nrog acetone thiab methanol sib xyaw hauv qhov sib piv ntawm 1:1 los ntawm qhov hnyav kom tau txais cov polymer dispersion nrog qhov concentration ntawm 6.5 wt.%. Npaj cov kua catalytic los ntawm kev sib xyaw 20g Bi2O3, ultrapure dej, nPA thiab ionomer dispersion hauv lub thawv 30ml. Cov khoom muaj 30 wt.% catalyst, qhov sib piv ntawm ionomer rau catalyst ntawm 0.02 thiab qhov sib piv ntawm cawv rau dej ntawm 2:3 (40 wt.% nPA). Ua ntej sib tov, 70g ntawm Glen Mills 5mm zirconia sib tsoo khoom tau ntxiv rau hauv qhov sib tov. Cov qauv tau muab tso rau ntawm Fisherbrand ™ digital lub raj mis roller ntawm 80 rpm rau 26 teev. Cia cov kua mem zaum rau 20 feeb ua ntej thov. Bi2O3 kua mem tau siv rau ntawm Qualtech automatic applicator (QPI-AFA6800) siv 1/2″ x 16″ laboratory wirewound refill (RD Specialties - 60 mil diameter) ntawm 22 ° C. 5 mL ntawm catalytic kua mem tau siv rau ntawm 7.5 x 8 nti Sigraacet 39 BB carbon gas diffusion carrier (roj cell cia) los ntawm rod deposition ntawm qhov nruab nrab ceev ntawm 55 mm / sec. Hloov cov electrodes coated no mus rau qhov cub thiab qhuav ntawm 80 ° C. Cov txheej txheem txheej txheem ntawm tus pas nrig thiab cov duab ntawm GDE txheej txheem tau qhia nyob rau hauv Daim Duab S4a thiab b. Ib lub cuab yeej X-ray fluorescence (XRF) (Fischerscope® XDV-SDD, Fischer-Technolgy Inc. USA) tau lees paub tias qhov kev thauj khoom GDE uas tau txheej txheem yog 3.0 mg Bi2O3/cm2.
Rau cov qauv sib xyaw ua ke uas muaj anion exchange membrane (AEM) thiab perforated CEM. Nafion NC700 (Chemours, USA) nrog lub nominal thickness ntawm 15 µm tau siv ua txheej CEM. Lub anodic catalyst tau txau ncaj qha rau ntawm FEM nrog ionomer rau carbon piv ntawm 0.83 thiab thaj chaw npog ntawm 25 cm2. Txhawb nqa platinum nrog thaj chaw loj (50 wt.% Pt/C, TEC 10E50E, TANAKA hlau muaj nqis) nrog kev thauj khoom ntawm 0.25 mg Pt/cm2 tau siv ua anode catalyst. Nafion D2020 (Ion Power, USA) tau siv ua ionomer rau txheej anode ntawm catalyst. CEM perforation yog ua los ntawm kev txiav cov kab sib luag ntawm CEM zaj duab xis ntawm 3 hli sib nrug. Cov ntsiab lus ntawm cov txheej txheem perforation tau qhia hauv Cov Duab S12b thiab c. Siv X-ray computed tomography, nws tau lees paub tias qhov sib txawv ntawm qhov perforation yog 32.6 μm, raws li pom hauv Daim Duab S12d thiab e. Thaum lub sijhawm sib sau ua ke ntawm tes, daim nyias nyias CEM uas muaj catalyst coated perforated tau muab tso rau ntawm daim ntawv Toray 25 cm2 (5 wt% PTFE kho, Fuel Cell Store, USA). Daim nyias nyias AEM (PiperION, Versogen, USA) nrog qhov tuab ntawm 25, 40 lossis 80 μm tau muab tso rau saum CEM thiab tom qab ntawd rau ntawm GDE cathode. Daim nyias nyias AEM tau txiav ua 7.5 × 7.5 cm daim los npog tag nrho cov dej ntws thiab tsau ib hmos hauv 1 M potassium hydroxide kua ua ntej sib sau ua ke. Ob qho tib si anode thiab cathode siv PTFE spacers uas tuab txaus kom ua tiav qhov zoo tshaj plaws GDE compression ntawm 18%. Cov ntsiab lus ntawm cov txheej txheem sib sau ua ke roj teeb tau pom hauv Daim Duab S12a.
Thaum lub sijhawm sim, lub cell sib dhos tau khaws cia ntawm 60 ° C (30, 60, thiab 80 ° C rau kev kawm txog qhov kub thiab txias) nrog 0.8 L / feeb ntawm cov roj hydrogen xa mus rau anode thiab 2 L / feeb ntawm cov pa roj carbon dioxide xa mus rau cathode. Ob qho tib si cov pa anodic thiab cathodic tau humidified ntawm 100% qhov sib piv ntawm cov av noo thiab 259 kPa qhov tseeb cathodic siab. Thaum lub sijhawm ua haujlwm, cov pa roj cathode tau sib xyaw nrog 1 M KOH kua ntawm tus nqi ntawm 2 mL / feeb los txhawb kev siv cathode catalyst txaj thiab ionic conduction. Sib tov cov dej ntawm anode roj nrog dej deionized ntawm tus nqi ntawm 10 ml / feeb kom tshem tawm cov kua qaub formic ntawm anode. Cov ntsiab lus ntawm cov khoom siv nkag thiab cov zis tau pom hauv Daim Duab S5. Cov pa roj cathode tso tawm muaj CO2 thiab tsim CO thiab H2. Cov pa dej raug tshem tawm los ntawm lub condenser (cov cua sov qis kub ntawm 2 ° C). Cov roj seem yuav raug sau rau kev tshuaj xyuas lub sijhawm roj. Cov dej ntws anode kuj tseem yuav hla dhau lub condenser kom cais cov kua ntawm cov roj. Cov dej khib nyiab yuav raug sau rau hauv cov vials huv thiab tshuaj xyuas siv cov kua chronometry los ntsuas cov formic acid tsim tawm. Kev ntsuam xyuas electrochemical tau ua tiav siv Garmy potentiostat (tus lej siv 30K, Gamry, Tebchaws Meskas). Ua ntej ntsuas qhov polarization curve, lub cell tau conditioned 4 zaug hauv qhov ntau ntawm 0 txog 250 mA / cm2 siv linear voltammetry nrog tus nqi scan ntawm 2.5 mA / cm2. Cov polarization curves tau txais hauv hom galvanostatic nrog lub cell tuav ntawm qee qhov tam sim no ceev rau 4 feeb ua ntej kuaj cov roj cathode thiab cov kua anolyte.
Peb siv lub electrode hydrogen hauv MEA los cais cov cathode thiab anodic potentials. Cov qauv ntawm lub electrode siv tau qhia nyob rau hauv Daim Duab S6a. Ib daim nyias nyias Nafion (Nafion 211, IonPower, USA) tau siv ua tus choj ionic los txuas lub nyias nyias MEA thiab lub electrode siv. Ib kawg ntawm daim ntawv Nafion tau txuas nrog lub electrode diffusion gas 1 cm2 (GDE) uas muaj 0.25 mg Pt/cm2 (50 wt% Pt/C, TEC10E50E, TANAKA Precious Metals) uas muab tso rau ntawm daim ntawv carbon 29BC (Fuel Cell Store, USA). Cov khoom siv polyetheretherketone (PEEK) tshwj xeeb tau siv los kaw cov pa roj thiab xyuas kom meej tias muaj kev sib cuag zoo ntawm GDE thiab Nafion strips, thiab los txuas lub electrode siv rau lub roj teeb siv. Lwm qhov kawg ntawm daim ntawv Nafion txuas nrog ntug ntawm lub roj teeb CEM. Daim Duab S6b qhia txog qhov seem ntawm lub electrode siv uas sib xyaw nrog MEA.
Tom qab cov pa roj tawm dhau los ntawm lub condenser thiab lub tshuab cais roj-kua, cov qauv roj raug coj los ntawm cathode. Cov roj uas tau sau tau raug tshuaj xyuas tsawg kawg peb zaug siv 4900 Micro GC (10 μm molecular sieve, Agilent). Cov qauv tau sau rau hauv cov hnab roj inert ntau txheej aluminium foil Supel™ (Sigma-Aldrich) rau lub sijhawm teev tseg (30 vib nas this) thiab muab ntxig rau hauv microgas chromatograph hauv ob teev tom qab sau. Qhov kub ntawm kev txhaj tshuaj tau teeb tsa ntawm 110 ° C. Carbon monoxide (CO) thiab hydrogen (H2) tau raug cais tawm ntawm lub kem MS5A uas muaj cua sov (105 ° C) (28 psi) 10 m siv argon (Matheson Gas-Matheson Purity) ua cov roj nqa. Cov kev sib txuas no raug ntes siv lub Thermal Conductivity Detector (TCD) uas ua tiav. GC chromatograms thiab CO thiab H2 calibration curves tau qhia hauv Daim Duab S7. Cov kua qaub formic tau sau los ntawm lub anode rau lub sijhawm teev tseg (120 vib nas this) thiab lim siv lub lim PTFE 0.22 μm rau hauv 2 mL vials. Cov khoom ua kua hauv cov vials tau soj ntsuam siv Agilent 1260 Infinity II bioinert high-performance liquid chromatography (HPLC) system, uas 20 μl ntawm cov qauv tau txhaj los ntawm autosampler (G5668A) nrog lub theem mobile ntawm 4 mM sulfuric acid (H2SO4). ) ntawm tus nqi ntws ntawm 0.6 ml / min (quaternary twj tso kua mis G5654A). Cov khoom tau sib cais ntawm lub qhov cub kub (35 ° C, kem qhov cub G7116A) Aminex HPX-87H 300 × 7.8 mm (Bio-Rad) ua ntej los ntawm Micro-Guard Cation H guard kem. Formic acid tau ntes tau siv lub diode array detector (DAD) ntawm qhov ntev ntawm 210 nm thiab bandwidth ntawm 4 nm. Cov HPL chromatogram thiab formic acid standard calibration curve tau qhia nyob rau hauv Daim Duab S7.
Cov khoom siv roj (CO thiab H2) FE raug suav siv cov qauv hauv qab no, thiab tag nrho cov moles ntawm cov roj raug suav siv cov qauv roj zoo tagnrho:
Ntawm lawv: \({n}_{i}\): tus naj npawb ntawm cov electrons hauv kev tshuaj electrochemical. \(F\): Faraday tus nqi tas mus li. \({C}_{i}\): HPLC kua khoom concentration. \(V\): ntim ntawm cov kua qauv sau dhau lub sijhawm teem t. \(j\): tam sim no ceev. \(A\): Geometric cheeb tsam ntawm lub electrode (25 cm2). \(t\): lub sijhawm kuaj. \(P\): siab kiag li. \({x}_{i}\): Mole feem pua ​​ntawm cov roj txiav txim siab los ntawm GC. \(R\): roj tas mus li. \(T\): kub.
Qhov kev sib sau ua ke ntawm cov anodic cations tau ntsuas siv cov inductively coupled plasma atomic emission spectroscopy (ICP-OES). Cov cations uas yuav leach lossis diffuse rau hauv anode suav nrog Ti, Pt, Bi thiab K. Tsuas yog K, tag nrho lwm cov cations nyob hauv qab qhov kev txwv tsis pub kuaj pom. Cov ions tsim nyob rau hauv cov tshuaj tawm hauv anode kom khub nrog protons lossis lwm yam cations. Yog li ntawd, qhov huv ntawm formic acid tuaj yeem suav ua
Kev tsim tawm ntawm Formate/FA sawv cev rau qhov ntau ntawm FA tsim tawm ib kWh ntawm hluav taws xob siv siv ib qho kev teeb tsa MEA tshwj xeeb, hauv mol/kWh. Nws yog xam raws li qhov ceev tam sim no, lub zog hluav taws xob ntawm tes thiab Faraday efficiency nyob rau hauv cov xwm txheej ua haujlwm tshwj xeeb.
Xam qhov ntau ntawm cov kua qaub formic oxidized ntawm lub anode raws li qhov sib npaug ntawm tag nrho. Peb qhov kev sib tw tshwm sim ntawm cathode: hydrogen evolution, txo CO2 rau CO, thiab txo CO2 rau formic acid. Vim tias peb muaj cov txheej txheem oxidation formic acid hauv Anton, formic acid FE tuaj yeem faib ua ob ntu: formic acid sau thiab formic acid oxidation. Qhov sib npaug ntawm tag nrho tuaj yeem sau ua:
Peb siv GC los ntsuas qhov ntau ntawm cov formic acid, hydrogen, thiab CO uas HPLC sau tau. Nws yuav tsum tau sau tseg tias feem ntau ntawm cov formic acid tau sau los ntawm anode siv qhov kev teeb tsa uas tau pom hauv Daim Duab Ntxiv S5. Qhov ntau ntawm cov formate sau los ntawm cathode chamber tsis tseem ceeb, kwv yees li ob qhov kev txiav txim ntawm qhov loj me, thiab tsawg dua 0.5% ntawm tag nrho cov nyiaj ntawm SC.
Tus qauv thauj mus los tas mus li siv ntawm no yog raws li cov haujlwm yav dhau los ntawm cov kab ke zoo sib xws34. Ib qho kev sib txuas ntawm Poisson-Nerst-Planck (PNP) cov kab zauv yog siv los txiav txim siab qhov concentration ntawm dej thiab electrostatic potential hauv cov theem hluav taws xob thiab ionically conducting. Ib qho kev piav qhia ntxaws ntawm cov kab zauv hauv qab thiab cov qauv geometry tau muab rau hauv SI.
Lub kaw lus no txiav txim siab qhov kev sib xyaw ntawm yim cov tshuaj aqueous (\({{{{{{\rm{C}}}}}}}{{{{{{\rm{O}}}}}}}}}}_{2 \left ({{{{{\rm{aq}}}}}}\right)}\), \({{{{{{\rm{H}}}}}}}}}}^{+ }\ ), \ ({{{{\rm{O}}}}}}{{{{{{\rm{H}}}}}}}^{-}\), \({{{ {{ {\rm{ HCO}}}}}}}}_{3}^{-}\), \({{{{{{\rm{CO}}}}}}}_{3}^{ 2-} \ ),\ ({{{{\rm{HCOOH}}}}}}}}}}\), \({{{{{{{\rm{HCOO}}}}}}}}}}^{- }\) thiab \({{{ {{{\rm{K}}}}}}}^{+}\)), electrostatic potential hauv theem ionic conducting (\({\phi }_{I}\ )) thiab anodic thiab cathodic electron conductivity. Cov peev xwm electrostatic hauv theem (\({\phi }_{A}\) thiab \({\phi }_{C}\) feem). Hloov chaw, tsis yog qhov tsis muaj hluav taws xob hauv zos lossis cov haujlwm faib tawm them nqi tau paub, thaj chaw them nqi tau daws ncaj qha siv Poisson tus qauv; Txoj hauv kev no tso cai rau peb los ua qauv ncaj qha rau Donnan repulsion effects ntawm CEM | AEM, CEM | Pore, thiab AEM | Pore interfaces. Tsis tas li ntawd, porous electrode theory (PET) yog siv los piav qhia txog kev thauj mus los them nqi hauv cov txheej anodic thiab cathodic ntawm cov catalyst. Raws li qhov zoo tshaj plaws ntawm cov kws sau ntawv paub, cov haujlwm no sawv cev rau thawj daim ntawv thov ntawm PET hauv cov kab ke nrog ntau thaj chaw them nqi.
Cov qauv cathode GDE BOT thiab EOT tau sim siv Zeiss Xradia 800 Ultra nrog 8.0 keV X-ray qhov chaw, kev nqus thiab hom teb dav dav, thiab kev sib xyaw duab1. 901 daim duab tau sau los ntawm -90 ° txog 90 ° nrog lub sijhawm raug 50 vib nas this. Kev tsim kho dua tshiab tau ua tiav siv lub lim dej rov qab nrog qhov loj me voxel ntawm 64 nm. Kev tshuaj xyuas ntawm kev faib tawm thiab kev faib tawm qhov loj me ntawm cov khoom me me tau ua tiav siv cov lej sau tshwj xeeb.
Kev ntsuas tus yam ntxwv ntawm lub tshuab hluav taws xob suav nrog kev muab cov MEAs sim tso rau hauv epoxy resin los npaj rau kev txiav ultrathin nrog rab riam pob zeb diamond. Qhov seem ntawm txhua MEA raug txiav kom tuab li ntawm 50 txog 75 nm. Lub tshuab hluav taws xob xa hluav taws xob Talos F200X (Thermo Fisher Scientific) tau siv rau kev ntsuas lub tshuab hluav taws xob xa hluav taws xob (STEM) thiab kev ntsuas X-ray spectroscopy (EDS). Lub tshuab hluav taws xob no muaj lub tshuab EDS Super-X nrog 4 lub qhov rai SDD detectors thiab ua haujlwm ntawm 200 kV.
Cov qauv diffraction X-ray hmoov (PXRD) tau txais ntawm Bruker Advance D8 hmoov X-ray diffractometer nrog Ni-filtered Cu Kα hluav taws xob ua haujlwm ntawm 40 kV thiab 40 mA. Qhov ntau ntawm kev luam theej duab yog txij li 10 ° txog 60 °, qhov loj ntawm cov kauj ruam yog 0.005 °, thiab qhov ceev ntawm kev tau txais cov ntaub ntawv yog 1 vib nas this ib kauj ruam.
Lub RAS spectrum ntawm ntug ntawm Bi2O3 Bi L3 catalyst tau ntsuas ua haujlwm ntawm lub peev xwm siv lub cell ua hauv tsev. Bi2O3 catalytic ionomer number tau npaj siv 26.1 mg Bi2O3 sib xyaw nrog 156.3 μL ionomer kua (6.68%) thiab neutralized nrog 1 M KOH, dej (157 μL) thiab isopropyl cawv (104 μL) kom tau txais ionomer number. Tus coefficient catalyst yog 0.4. Cov number tau siv rau graphene ntawv hauv cov chaw rectangular (10 × 4 hli) kom txog thaum Bi2O3 catalyst loading mus txog 0.5 mg / cm2. Tus so ntawm graphene ntawv yog coated nrog Kapton los cais cov cheeb tsam no ntawm electrolyte. Lub catalyst-coated graphene ntawv tau ntxig ntawm ob lub PTFEs thiab ruaj ntseg rau lub cev cell (PEEK) nrog screws, Daim Duab S8. Hg / HgO (1 M NaOH) ua haujlwm ua tus siv hluav taws xob, thiab cov ntawv carbon tau ua haujlwm ua tus counter electrode. Lub Hg/HgO reference electrode tau calibrated siv ib lub platinum wire immersed nyob rau hauv hydrogen-saturated 0.1 M KOH los hloov tag nrho cov potentials ntsuas tau mus rau ib qho reversible hydrogen electrode (RHE). XRD spectra tau txais los ntawm kev saib xyuas lub potential ntawm Bi2O3/graphene sheet working electrode immersed nyob rau hauv 0.1 M KOH, cua sov rau 30 °C. Lub electrolyte circulates nyob rau hauv lub roj teeb, nrog rau lub electrolyte inlet nyob rau hauv qab ntawm lub cell thiab lub qhov hluav taws xob nyob rau sab saum toj kom ntseeg tau tias lub electrolyte kov lub catalyst txheej thaum npuas tsim. Ib tug CH Instruments 760e potentiostat tau siv los tswj lub potential electrode ua haujlwm. Lub potential sequence yog ib qho qhib circuit potential: -100, -200, -300, -400, -500, -800, -850, -900, -1000, -1100, -1500 thiab +700 mV nyob ntawm RHE. Tag nrho cov iR potentials tau raug kho.
Bi L3 ntug (~ 13424 eV rau Bi hlau) X-ray absorption fine structure (XAFS) spectroscopy tau ua tiav ntawm channel 10-ID, Advanced Photon Source (APS), Argonne National Fluorescence Laboratory. National Model Measurement Laboratory. Ib lub monochromator ob-crystal Si (111) txias nrog kua nitrogen tau siv los kho lub zog X-ray, thiab daim iav rhodium-coated tau siv los txo cov ntsiab lus harmonic. Lub zog scan tau hloov pauv ntawm 13200 txog 14400 eV, thiab fluorescence tau ntsuas siv 5 × 5 silicon PIN diode array tsis muaj cov lim dej lossis Soller slits. Lub zog hla xoom ntawm qhov thib ob derivative tau calibrated ntawm 13271.90 eV los ntawm L2 ntug ntawm Pt ntawv ci. Vim yog qhov tuab ntawm lub cell electrochemical, nws tsis tuaj yeem ntsuas lub spectrum ntawm tus qauv siv tib lub sijhawm. Yog li, qhov kev hloov pauv ntawm scan-rau-scan hauv lub zog X-ray uas tshwm sim yog ± 0.015 eV raws li kev ntsuas rov ua dua thoob plaws hauv kev sim. Lub thickness ntawm Bi2O3 txheej ua rau muaj qee qib ntawm kev nqus ntawm fluorescence; cov electrodes tswj hwm qhov kev taw qhia ruaj khov piv rau lub teeb pom kev thiab lub tshuab ntes, ua rau txhua qhov kev luam theej zoo ib yam. Near-field XAFS spectrum tau siv los txiav txim siab lub xeev oxidation thiab cov tshuaj lom neeg ntawm bismuth los ntawm kev sib piv nrog thaj tsam XANES ntawm Bi thiab Bi2O3 cov qauv siv cov txheej txheem sib xyaw ua ke ntawm Athena software (version 0.9.26). los ntawm code IFEFFIT 44.
Cov ntaub ntawv txhawb nqa cov lej hauv tsab xov xwm no thiab lwm cov lus xaus ntawm txoj kev tshawb fawb no muaj los ntawm tus sau ntawv sib xws thaum thov.
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