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Carbon dioxide chu formic acid-a electrochemical tihtlem hi carbon dioxide hman dan tihchangtlunna kawng beisei awm tak a ni a, hydrogen dahkhawmna atana hman theih a ni. He hnathawhnaah hian carbon dioxide atanga formic acid direct electrochemical synthesis atan zero-gap membrane electrode assembly architecture siam a ni. Technology lama hmasawnna pawimawh tak chu perforated cation exchange membrane a ni a, hei hi forward biased bipolar membrane configuration-a hman a nih chuan membrane interface-a formic acid siam chu anodic flow field kaltlangin 0.25 M electrolysis hmangin scale-up leh commercialization lama inthlak chak zawk a ni. 25 cm2 cell-ah chuan perforated cation exchange membrane configuration hian formic acid tan <2 V leh 300 mA/cm2-ah >75% Faraday efficiency a pe a ni. Chu aia pawimawh zawk chu darkar 55 chhunga 200 mA/cm2-a stability test-ah Faraday efficiency leh cell voltage stable tak a awm tih hmuhchhuah a ni. Tuna formic acid siam dan hman mek nena cost parity neih theih dan tur tarlanna atan techno-economic analysis hman a ni.
Renewable electricity hmanga carbon dioxide chu formic acid-a electrochemical tihhniam hian fossil fuel hmanga siam dan pangngai nena khaikhin chuan 75%1 thlengin a siam chhuah man a tihhniam tih hmuhchhuah a ni. Literature-a tarlan angin2,3, formic acid hian hmanna hrang hrang a nei a, hydrogen dahkhawmna leh phurh chhuahna hmanraw tangkai leh man tlawm tak atanga chemical industry4,5 emaw biomass industry6 tana feedstock thlenga hman theih a ni. Formic acid hi metabolic engineering hmanga a hnu lama sustainable jet fuel intermediate-a chantirna tur feedstock atan pawh hmuhchhuah a ni tawh7,8. Formic acid economics1,9 lo awm chhoh zel avang hian research work engemaw zatah catalyst selectivity tihchangtlun dan tur ngaihtuah a ni10,11,12,13,14,15,16. Mahse, hmalakna tam tak chu H-cell te tak te emaw, current density hniam (<50 mA/cm2)-a thawk liquid flow cell emaw lam ngaihtuah chhunzawm zel a ni. Cost tihtlem, commercialization neih theihna tur leh a hnu lama market penetration tihpun nan electrochemical carbon dioxide reduction (CO2R) chu current density sang tak (≥200 mA/cm2) leh Faraday efficiency (FE)17-ah tih a ngai a, chutih rualin material hman tam ber tur leh Technology fuel cells atanga battery components hman leh water electrolysis hmang hian CO2R devices te chu scale-a economy te chu an hmang tangkai thei a ni Chu bakah, thil siam chhuah hlawkna tihpun nan leh downstream processing dang tih belh loh nan formate salt aiin formic acid hi final product atan hman tur a ni19.
Hemi kawngah hian tun hnaiah industry lama kaihhnawih CO2R formate/formic acid based gas diffusion electrode (GDE) device siam chhuah tumin hmalak a ni. Fernandez-Caso et al.20 te review kimchang chuan CO2 chu formic acid/formate-a tihtlem chhunzawm zelna tur electrochemical cell configuration zawng zawng a khaikhawm a. A tlangpuiin configuration awmsa zawng zawng hi chi thum ah then theih a ni a, chungte chu 1. Flow-through catholytes19,21,22,23,24,25,26,27, 2. Single membrane (cation exchange membrane (CEM)28 emaw anion exchange membrane (AEM)29 leh 3. Sandwich configuration15,30,31,32. Simplified cross-sections of these configurations are shown in Figure 1a cathode chu carbon substrate-ah 1.27 mm thick catholyte layer, 500 mA/cm2-ah 90% FE 35 thleng a awm thei a ni. Li et al., CEM configuration pakhat hmangin, fractional current density 51.7 mA/cm2-ah FE 29 93.3% an hmu a, Diaz-Sainz et al.28 chuan CEM membrane pakhat hmanga current density 45 mA/cm2-ah filter press an hmang a, mahse, method zawng zawng hian product duh zawk aiin formate an siam chhuak zawk a ni requirements, CEM configuration-ah chuan KCOOH ang chi format te chu GDE leh flow field-ah rang takin a pungkhawm thei a, chu chuan transport restrictions a thlen a, a tawpah cell failure a thlen thei bawk.
CO2R to formate/formic acid conversion device configuration langsar ber pathum leh he zirchiannaa architecture rawt te khaikhin. b Literature-a catholyte configuration, sandwich configuration, single CEM configuration (Supplementary Table S1-a tarlan) leh kan hnathawhna atana current leh formate/formic acid yield zawng zawng tehkhin dan. Open marks hian formate solution siam chhuahna a tarlang a, solid marks hian formic acid siam chhuahna a tarlang bawk. *Anode-a hydrogen hmanga configuration tarlan. c Zero-gap MEA configuration hmanga composite bipolar membrane hmanga perforated cation exchange layer forward bias mode-a thawk.
Formate siam chhuah loh nan Proietto et al. 32 chuan splitless filter press configuration an hmang a, chutah chuan deionized water chu interlayer kaltlangin a luang chhuak a ni. He system hian tuna density range 50–80 mA/cm2 ah >70% CE a thleng thei a ni. Chutiang bawkin Yang leh a thawhpuiten an sawi bawk. 14 chuan formic acid siam chhuahna tichak turin CEM leh AEM inkarah solid electrolyte interlayer hman a rawt a. Yang et al.31,36 chuan 5 cm2 cell-ah 200 mA/cm2-ah 91.3% FE an hmu a, 6.35 wt% formic acid solution an siam chhuak a ni. Xia leh a thawhpuiten an sawi. Configuration ang chiah hmang hian carbon dioxide (CO2) chu formic acid FE-ah 83%-in 200 mA/cm2-ah a chantir a, system durability chu darkar 100 leh minute 30 chhung test a ni. Small-scale result beisei awm tak ni mahse, porous ion exchange resins man to leh complexity a san avangin interlayer configuration te chu system lian zawk (eg, 1000 cm2) ah scale a harsa hle.
Design hrang hrangte net effect hmuh theih nan a hmaa kan sawi tawh system zawng zawngte kWh khata formate/formic acid siam chhuah zat chu tabulate-in Figure 1b-ah kan plot a. Hetah hian a chiang a, catholyte emaw interlayer emaw awmna system eng pawh hian current density hniam takah a performance a peak ang a, current density sang zawkah a degrade ang a, chutah chuan ohmic limit hian cell voltage a tichiang thei a ni. Chubakah, energy-efficient CEM configuration hian kWh khatah molar formic acid siam chhuah tam ber ni mahse, salt buildup hian current density sang takah performance degradation rang tak a thlen thei a ni.
A hmaa kan sawi tawh ang khan failure modes tihziaawm nan membrane electrode assembly (MEA) kan siam a, chutah chuan composite forward biased BPM leh perforated cation exchange membrane (PCEM) a awm a. Architecture chu Figure 1c-ah hian kan hmu a. Hydrogen (H2) chu anode chhungah dahin hydrogen oxidation reaction (HOR) hmangin proton siam a ni. BPM system-ah hian PCEM layer dah a ni a, chu chuan cathode-a formate ion siamte chu AEM kaltlangin a kal thei a, protons nen an inzawm khawm a, CEM-a BPM interface leh interstitial pores-ah formic acid an siam a, chutah chuan GDE anode leh flow field kaltlangin an chhuak thei a ni. . He configuration hmang hian 25 cm2 cell area atan <2 V leh 300 mA/cm2 ah formic acid >75% FE kan hmu a. A pawimawh ber chu, design hian fuel cell leh water electrolysis plant-te tana sumdawnna atana hman theih component leh hardware architecture te a hmang a, hei hian scale-na hun rei zawk a siamsak a ni. Catholyte configuration-ah hian catholyte flow chamber a awm a, hei hian gas leh liquid phase inkarah pressure imbalance a siam thei a, a bik takin cell configuration lian zawkah chuan. Fluid flow porous layer nei sandwich structure tan chuan, intermediate layer chhunga pressure drop leh carbon dioxide pungkhawm tihtlem nan porous intermediate layer optimize turin theihtawp chhuah nasa tak a ngai a ni. Heng pahnih hian cellular communication a tibuai thei a ni. Tin, free-standing thin porous layer lian tak siam pawh a harsa hle. Chumi danglamna chu, configuration thar ruahman chu zero-gap MEA configuration a ni a, flow chamber emaw intermediate layer emaw a awm lo. Electrochemical cell awm tawh dangte nena khaikhin chuan he configuration ruahman hi a danglam bik a, scalable, energy-efficient, zero-gap configuration-a formic acid direct synthesis a phalsak a ni.
Hydrogen evolution tihtawp nan CO2 tihtlem tumna lian tham tak takah chuan MEA leh AEM membrane configuration te chu molar concentration sang tak electrolyte (eg, 1-10 M KOH) te nen inzawmkhawmin cathode-ah alkaline condition siam a ni (Figure 2a-a kan hmuh ang hian). Heng configuration-ah hian cathode-a formate ion lo awmte chu negative charged species angin membrane kaltlangin an kal a, chutah chuan KCOOH a lo piang a, anodic KOH stream hmangin system atang chuan a chhuak ta a ni. Figure 2b-a kan hmuh angin formate FE leh cell voltage chu a tir lamah chuan a tha hle nachungin, stability testing hmangin FE chu 10 h chauh chhungin 30% velin a tlahniam a ni (Figure S1a–c). Hriat tur chu 1 M KOH anolyte hman hi alkaline oxygen evolution reaction (OER) system-a anodic overvoltage tihtlem nan leh cathode catalyst bed chhunga ion accessibility neih theihna turin a pawimawh hle Anolyte concentration chu 0.1 M KOH-a tihhniam a nih chuan cell voltage leh formic acid oxidation (formic acid hloh) te hi a pung vek a (Figure S1d), hei hian zero-sum trade-off a entir a ni. Formate oxidation degree chu overall mass balance hmangin an zir chiang a; chipchiar zawka hriat duh chuan “Methods” tih thupuiah hian en rawh. MEA leh single CEM membrane configuration hmanga performance pawh zirchian a ni a, a result chu Figure S1f,g-ah hian tarlan a ni. Cathode atanga FE formate lakkhawm chu test tan tirh khan 200 mA/cm2 ah >60% a ni a, mahse a hmaa kan sawi tawh ang khan cathode salt a punkhawm avangin darkar hnih chhungin a chhe nghal vat a ni (Figure S11).
Zero-gap MEA schematic a ni a, cathode-ah CO2R a awm a, anode-ah hydrogen oxidation reaction (HOR) emaw OER emaw a awm a, a inkar ah AEM membrane pakhat a awm bawk. b He configuration atan hian FE leh cell voltage chu anode-ah 1 M KOH leh OER luang chhuak a ni. Error bar hian tehna hrang hrang pathum standard deviation a entir a. in FE leh system cell voltage ah H2 leh HOR chu anode ah a awm. Formate leh formic acid siam dan thliar hrang nan rawng hrang hrang hman a ni. d MEA schematic diagram a BPM chu a laiah hmalam pan a ni. He configuration hmang hian FE leh battery voltage leh 200 mA/cm2-a hun hman a ni. f Test tawi neih hnua forward-biased BPM MEA cross-sectional image.
Formic acid siam chhuah nan hian anode-a Pt-on-carbon (Pt/C) catalyst-ah hydrogen supply a ni. Figure 2d-a kan hmuh angin, formic acid siam chhuah theihna turin anode-a proton siamtu forward-biased BPM chu a hmain an lo zirchiang tawh a ni. BPM tuning unit chu minute 40 chhung zet current 200 mA/cm2-a a thawh hnuah a chhia a, chu chu voltage surge 5 V aia sangin a zui bawk (Fig. 2e). Test zawhah CEM/AEM interface-ah delamination chiang tak hmuh a ni. Formate bakah hian anion carbonate, bicarbonate leh hydroxide te pawh AEM membrane kal tlangin CEM/AEM interface-a proton te nen an inrem thei a, CO2 gas leh liquid water a siam thei a, chu chuan BPM delamination (Fig. 2f) leh , a tawpah chuan cell failure a thlen thei a ni.
A chunga kan sawi tak configuration-a performance leh failure mechanisms atanga chhut chuan Figure 1c-a kan hmuh ang leh Figure 3a38-a chipchiar taka tarlan angin MEA architecture thar siam tura rawtna siam a ni. Hetah hian PCEM layer hian CEM/AEM interface atanga formic acid leh anion te kalna tur kawng a siam a, chu chuan thil awmkhawm chu a ti tlem a ni. Chutih rual chuan PCEM interstitial pathway hian formic acid chu diffusion medium leh flow field-ah a hruai lut a, hei hian formic acid oxidation awm theihna a ti tlem a ni. AEM thickness 80, 40 leh 25 mm hmanga polarization result chu Figure 3b-ah hian tarlan a ni. Beisei ang ngeiin AEM thickness a san chuan cell voltage pumpui chu a sang chho zel a, mahse AEM thick zawk hman hian formic acid back diffusion a veng a, chu chuan cathode pH a tisang a, H2 production a ti tlem bawk (Fig. 3c–e).
a AEM leh perforated CEM leh formic acid transport pathway hrang hrang hmanga MEA structure entir. b Current density hrang hrang leh AEM thickness hrang hranga cell voltage. in EE ah current density hrang hrangah AEM thickness 80 μm (d) 40 μm, e) 25 μm a ni. Error bar hian sample hrang hrang pathum atanga standard deviation tehna a entir a ni. f AEM thickness hrang hranga CEM/AEM interface-a formic acid concentration leh pH value simulation result. f AEM film thickness hrang hrang nei catalyst cathode layer-a PC leh pH. g CEM/AEM interface leh perforation hmanga formic acid concentration chu two-dimensional distribution.
Figure S2 hian Poisson-Nernst-Planck finite element modeling hmangin MEA thickness huam chhunga formic acid concentration leh pH insem dan a tarlang a. CEM/AEM interface-ah hian formic acid concentration sang ber 0.23 mol/L hmuh a ni hi thil mak a ni lo, he interface-ah hian formic acid a lo awm avangin. AEM kaltlangin formic acid concentration chu AEM thickness a san chuan a tlahniam chak zawk a, hei hian mass transfer laka invenna nasa zawk leh back diffusion avanga formic acid flux tlem zawk a tilang a ni. Figure 3 f leh g-ah hian back diffusion avanga cathode catalyst bed-a pH leh formic acid value leh formic acid concentration two-dimensional distribution te tarlan a ni. AEM membrane a thim poh leh cathode bulah formic acid a tam zawk a, cathode pH chu acidic a lo ni ta a ni. Chuvangin, AEM membrane thick zawk hian ohmic loss sang zawk thlen mahse, formic acid chu cathode-a back diffusion venna atan leh FE formic acid system thianghlimna sang tak tihpun nan a pawimawh hle. A tawp berah chuan AEM thickness 80 μm-a tihpun chuan formic acid tan FE >75% <2 V-ah a awm a, 25 cm2 cell area-ah 300 mA/cm2 a awm bawk.
He PECM-based architecture stability test nan hian battery current chu darkar 55 chhung 200 mA/cm2-ah an dah a ni. Results zawng zawng chu Figure 4-ah hian tarlan a ni a, darkar 3 hmasa ber result chu Figure S3-ah tarlan a ni. Pt/C anodic catalyst hman a nih chuan a hmasa ber min 30 chhungin cell voltage chu nasa takin a pung a (Figure S3a). Hun rei zawkah chuan cell voltage chu a awm reng mai a, chu chuan degradation rate 0.6 mV/h a pe a ni (Fig. 4a). Test tan tirh khan anode-a formic acid PV lakkhawm chu 76.5% a ni a, cathode-a hydrogen PV lakkhawm chu 19.2% a ni. Darkar khatna test hnuah hydrogen FE chu 13.8%-ah a tlahniam a, hei hian formate selectivity a ṭhatzia a tilang a ni. Mahse, system chhunga formic acid oxidation rate chu darkar 1 chhungin 62.7%-ah a tlahniam a, anodic formic acid oxidation rate chu test tan tirh lamah zero vel atanga 17.0%-ah a kai chho ta a ni. Chumi hnuah chuan experiment neih chhung hian H2, CO, formic acid FE leh formic acid anodic oxidation rate chu a nghet reng a ni. Darkar khatna chhunga formic acid oxidation a pun chhan hi PCEM/AEM interface-a formic acid awmkhawm vang a ni thei. Formic acid concentration a san chuan membrane perforation hmangin a chhuak mai bakah FEM ngei hmangin a diffuse a, Pt/C anode layer-ah a lut bawk. Formic acid hi 60°C-a liquid a nih avangin a khawlkhawm hian mass transfer lama harsatna a thlen thei a, hydrogen aiin oxidation duh zawk a thlen thei bawk.
a Cell voltage leh hun (200 mA/cm2, 60 °C) a ni. Inset-ah hian MEA cross-section, perforated EM hmanga optical microscope image a ni. Scale bar: 300 μm a ni. b Pt/C anode hmanga 200 mA/cm2-a hun a zirin PE leh formic acid thianghlimna.
Test tan tirh (BOT)-a sample te chu an inbuatsaih lai leh test tawp (EOT)-a 55 h stability test hnua an morphology chu nano-X-ray computed tomography (nano-CT) hmangin an characterize a, Figure 5 a-ah hian kan hmu a ni. EOT sample hian catalyst particle size lian zawk a nei a, a diameter chu 1207 nm a ni a, BOT tan chuan 930 nm a ni thung. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) hmanga thlalak leh energy-dispersive X-ray spectroscopy (EDS) hmanga result te chu Figure 5b-ah hian tarlan a ni. BOT catalyst layer-ah hian catalyst particle tenau zawk tam zawk bakah agglomerate lian zawk thenkhat a awm laiin, EOT stage-ah chuan catalyst layer hi hmun hrang hrang pahnih-ah then theih a ni a, pakhatah chuan solid particle lian zawk tak tak a awm a, pakhatah chuan porous region tam zawk a awm bawk. Particle te zawk awm zat. EDS image atanga a lan dan chuan solid particle lian tak takte chu Bi a tam hle a, metallic Bi pawh a ni thei a, porous region-ah chuan oxygen a tam hle bawk. Cell chu 200 mA/cm2-a kalpui a nih chuan cathode-a negative potential chuan Bi2O3 a tihtlem phah dawn a, hei hi a hnuaia in situ X-ray absorption spectroscopy result kan sawi tawhte hian a tilang chiang hle. HAADF-STEM leh EDS mapping result atanga a lan dan chuan Bi2O3 hian reduction process a paltlang a, chu chuan oxygen a hloh a, agglomerate chu metal particle lian zawkah a siam a ni. BOT leh EOT cathode-a X-ray diffraction pattern-te chuan EDS data hrilhfiahna chu a nemnghet (Fig. 5c): BOT cathode-ah hian crystalline Bi2O3 chauh hmuhchhuah a ni a, EOT cathode-ah crystalline bimetal hmuh a ni bawk. Bi2O3 cathode catalyst oxidation state-a cathode potential-in nghawng a neih dan hriatthiam nan open circuit potential (+0.3 V vs RHE) atanga -1.5 V (vs RHE) thlengin temperature an thlak danglam a. Bi2O3 phase hi RHE nena khaikhin chuan -0.85 V-ah a tlahniam tan tih hmuhchhuah a ni a, spectrum edge region-a white line intensity tlahniam chuan metallic Bi chu -1.1-ah RHE 90%-ah a tlahniam tih a tilang a ni. V chu RHE lakah a ni (Fig. 5d). Mechanism eng pawh ni se, cathode-a formate thlan theihna zawng zawng chu a bul berah chuan a danglam lo a, hei hi H2 leh CO FE leh formic acid siam dan atanga chhut a ni a, cathode morphology, catalyst oxidation state leh microcrystalline structure-ah danglamna nasa tak awm mah se.
a Nano-X-ray CT hmanga catalyst layer leh catalyst particle te insem darh dan chu Three-dimensional structure a ni. Scale bar: 10 μm a ni. b Top 2: BOT leh EOT catalyst-a cathode layer-a HAADF-STEM hmanga thlalak. Scale bar: 1 μm a ni. Bottom 2: EOT catalyst-a cathode layer-a HADF-STEM leh EDX image lian zawk. Scale bar: 100 nm a ni. c BOT leh EOT cathode sample-a X-ray diffraction pattern. d 0.1 M KOH-a Bi2O3 electrode in situ X-ray absorption spectra chu potential function angin (0.8 V to -1.5 V vs. RHE).
Formic acid oxidation tihkhawtlai hmanga energy efficiency tihchangtlunna tur kawng eng nge awm tih chiang taka hriat theih nan H2 reference electrode hmangin voltage hlohna thawhhlawkzia hriatchhuah a ni Current density 500 mA/cm2 aia tlem a nih chuan cathode potential chu -1.25 V hnuaiah a awm reng a, anodic potential hi hmunpui pahnih ah then a ni a, chungte chu exchange current density HOR leh a hmaa Bulter-Volmer equation-in a lo chhut tawh theoretical overvoltage HOR 40 te an ni a, a bak chu oxidation formic acid vang a ni. HOR41 nena khaikhin chuan reaction kinetics a slow zawk avangin anode-a formic acid oxidation reaction rate tlemte hian anodic potential nasa takin a tipung thei a ni. Results atanga a lan dan chuan formic acid anodic oxidation tihtawp vek chuan 500 mV vel overvoltage a ti bo thei a ni.
He estimate test nan hian anode inlet-a deionized water (DI) flow rate chu effluent formic acid concentration tihhniam nan an thlak danglam a ni. Figure 6b leh c-ah hian FE, formic acid concentration, leh cell voltage te chu anode-a DI flux 200 mA/cm2-a function angin a lang. Deionized water flow rate chu 3.3 mL/min atanga 25 mL/min a a san chuan anode-a formic acid concentration chu 0.27 mol/L atanga 0.08 mol/L ah a tlahniam a ni. Chumi nena khaikhin chuan Xia et al. 30 a formic acid concentration 1.8 mol/L chu 200 mA/cm2 ah hmuh a ni. Concentration tihhniam hian formic acid FE pumpui a ti tha a, formic acid back diffusion tlahniam avanga cathode pH chu alkaline a nih avangin H2 FE a tihhniam bawk. Maximum DI flow-a formic acid concentration tlahniam hian formic acid oxidation pawh a ti bo vek a, chu chuan 200 mA/cm2-ah total cell voltage 1.7 V aia tlem lo a siam a ni. Battery temperature hian overall performance a nghawng bawk a, a result chu Figure S10-ah hian kan hmu a ni. Mahse, PCEM-based architecture hian formic acid oxidation tihtawp kawngah energy efficiency nasa takin a tichangtlung thei a, chu chu formic acid lam hawia hydrogen selectivity tha zawk nei anodic catalyst hman hmang emaw, device operation hmang emaw pawh nise.
a 60 °C-a thawk cell reference H2 electrode, Pt/C anode leh 80 μm AEM hmanga Cell voltage tihchhiat. b Anodic deionized water flow rate hrang hrang hmanga FE leh formic acid concentration 200 mA/cm2-a lakkhawm. c Anode hian formic acid concentration hrang hrang a khawlkhawm chuan cell voltage chu 200 mA/cm2 a ni. Error bar hian tehna hrang hrang pathum standard deviation a entir a. d National industrial average electricity man US$0.068/kWh leh US$4.5/kg hydrogen hmanga deionized water flow rate hrang hranga performance a zirin hralh man tlem ber. (*: Anode-a formic acid oxidation state tlem ber chu 10 M FA anga ngaih a ni a, national average industrial electricity man chu $0.068/kWh a ni a, hydrogen chu $4.5/kg a ni. **: Oxidation state tlem ber chu formic acid anga ngaih a ni. Anode-a FA concentration chu 1.3 M anode a ni a, nakin lawka electric man beisei chu $0.03/kWh a ni a, leh dotted line hian market price 85 wt% FA a entir a ni.
Figure 5d-a kan hmuh ang hian fuel assembly-te hralhna man tlawm ber chu operating condition hrang hrang hnuaia hmuh theih nan techno-economic analysis (TEA) neih a ni. TEA atana hmanraw leh background data chu SI-ah hian hmuh theih a ni. Anode exhaust-a LC concentration a san chuan cell voltage sang zawk mah se, fuel assembly man zawng zawng chu separation cost a tlahniam avangin a tlahniam a ni. Catalyst siam emaw electrode technology hmanga formic acid anodic oxidation tih tlem theih a nih chuan cell voltage hniam zawk (1.66 V) leh effluent-a FA concentration sang zawk (10 M) te inzawmkhawm chuan electrochemical FA siamna senso chu 0.74 US dollars/kg (electricity atanga chhut)-ah a tihhniam ang. man) $0.068/kWh leh $4.5/kg hydrogen42. Chubakah, nakin lawka renewable electricity senso tur ruahman $0.03/kWh leh hydrogen $2.3/kg nena khaikhin chuan FA bawlhhlawh tui target chu maktaduai 1.3-ah tihhniam a ni a, chu chuan a tawp berah chuan siam chhuah senso tur ruahman chu US$0.66/kg43 a ni. Hei hi tuna market man nen tehkhin theih a ni. Chutiang chuan, nakin lawka electrode material leh structure-a hmalakna chuan anodization a tihtlem belh thei a, chutih rualin cell voltage hniam zawka hnathawh chuan LC concentration sang zawk a siam thei bawk.
A tawi zawngin, CO2 formic acid-a tihtlem theihna tur zero-gap MEA structure engemawzat kan zirchiang a, formic acid lo chhuak tur membrane mass transfer interface awlsam zawk nan perforated cation exchange membrane (PECM) telin composite forward-biased bipolar membrane awmna structure kan rawt a ni. . He configuration hian >96% formic acid a siam chhuak a, chu chu 0.25 M thleng (anode DI flow rate 3.3 mL/min-ah) a ni. DI flow rates sang zawk (25 mL/min)-ah chuan he configuration hian 25 cm2 cell area hmangin 1.7 V-ah current density >80% FE 200 mA/cm2 a pe a ni. Anodic DI rates (10 mL/min) hniam takah chuan PECM configuration chuan 200 mA/cm2-a testing 55 h chhung chu stable voltage leh formic acid FE level sang tak a vawng reng a ni. Sumdawnna lama hman theih catalyst leh polymeric membrane materials te stability leh selectivity sang tak chu optimized electrocatalyst nena inzawmkhawmin a tichak lehzual thei a ni. A hnu lama hnathawh turte chu formic acid oxidation tihtlem nan operating condition, anode catalyst selectivity, leh MEA structure siamrem te a ni ang a, chu chuan cell voltage hniam zawkah effluent concentrated zawk a siam ang. Heta formic acid atana carbon dioxide hman dan awlsam tak kan tarlan hian anolyte leh catholyte chamber, sandwich component, leh specialty materials mamawhna a titawp a, chu chuan cell energy efficiency a tipung a, system complexity a ti tlem a, scale up a awlsam phah a ni. Configuration ruahman hian nakin lawka technical leh economically viable CO2 conversion plant siamna tur platform a siam a ni.
A danglamna a awm loh chuan chemical grade material leh solvent zawng zawng chu an dawn angin hman vek a ni. Bismuth oxide catalyst (Bi2O3, 80 nm) hi US Research Nanomaterials, Inc. atangin lei a ni a, Polymer powder (AP1-CNN8-00-X) chu IONOMR atanga siam a ni. Omnisolv® brand N-propanol (nPA) leh tui thianghlim tak (18.2 Ω, Milli–Q® Advantage A10 tui tihthianghlimna system) te chu Millipore Sigma atangin lei a ni. ACS certified methanol leh acetone hi VWR Chemicals BDH® leh Fisher Chemical aṭangin lei a ni. Polymer powder chu acetone leh methanol inzawmkhawm nen 1:1 by weight ratio-in an pawlh a, polymer dispersion concentration 6.5 wt.% an hmu a ni. 30ml jar-ah Bi2O3 20g, ultrapure water, nPA leh ionomer dispersion te chu chawhpawlh la, catalytic ink siam rawh. Composition-ah hian catalyst 30 wt.%, ionomer leh catalyst mass ratio 0.02 leh alcohol leh tui mass ratio 2:3 (40 wt.% nPA) a awm a ni. Mixing hmain Glen Mills 5mm zirconia grinding material 70g chu mixture-ah hian dah a ni. Sample te chu FisherbrandTM digital bottle roller-ah 80 rpm-ah darkar 26 chhung dah a ni. Ink chu minute 20 vel thut tir la, i hnawih hmain. Bi2O3 ink chu Qualtech automatic applicator (QPI-AFA6800)-ah 1/2′′ x 16′′ laboratory wirewound refill (RD Specialties – 60 mil diameter) hmangin 22°C-ah hnawih a ni. Catalytic ink 5 mL chu 7.5 x 8 inch Sigraacet 39 BB carbon gas diffusion carrier (fuel cell storage)-ah rod deposition hmangin fixed average speed 55 mm/sec-ah dah a ni. Heng coated electrode te hi oven ah dah la, 80 °C ah vawt rawh. Rod coating kalphung leh GDE coating thlalak te chu Figure S4a leh b-ah hian tarlan a ni. X-ray fluorescence (XRF) instrument (Fischerscope® XDV-SDD, Fischer-Technolgy Inc. USA) chuan coated GDE loading chu 3.0 mg Bi2O3/cm2 a nih thu a nemnghet a ni.
Anion exchange membrane (AEM) leh perforated CEM awmna composite membrane configuration atan. CEM layer atan hian Nafion NC700 (Chemours, USA) nominal thickness 15 μm hman a ni. Anodic catalyst chu FEM-ah direct-in ionomer to carbon ratio 0.83 leh coverage area 25 cm2-a spray a ni. Anode catalyst atan hian supported platinum, a surface area lian tak (50 wt.% Pt/C, TEC 10E50E, TANAKA precious metal) loading 0.25 mg Pt/cm2 nei hman a ni. Catalyst anode layer atan ionomer atan Nafion D2020 (Ion Power, USA) hman a ni. CEM perforation hi CEM film-a parallel line 3mm inkar a cut hmanga tih a ni. Perforation kalphung chipchiar tak chu Figure S12b leh c-ah hian tarlan a ni. X-ray computed tomography hmangin perforation gap chu 32.6 μm a ni tih finfiah a ni a, Figure S12d leh e. Cell assembly lai hian catalyst-coated perforated CEM membrane chu 25 cm2 Toray paper (5 wt% PTFE treated, Fuel Cell Store, USA)-ah dah a ni. CEM chungah AEM membrane (PiperION, Versogen, USA) a thuk zawng 25, 40 emaw 80 μm emaw dah a ni a, chutah chuan GDE cathode chungah dah a ni. AEM membrane chu flow field zawng zawng khuh turin 7.5 × 7.5 cm-ah then a ni a, assembly hmain 1 M potassium hydroxide solution-ah zan khat chhung dah a ni. Anode leh cathode pahnih hian PTFE spacer an hmang a, chu chu a thuk tawk a, GDE compression tha ber 18% a awm thei a ni. Battery assembly kalphung kimchang chu Figure S12a-ah hian tarlan a ni.
Test neih chhung hian assembled cell chu 60 °C (temperature dependence study atan 30, 60, leh 80 °C)-ah an dah a, anode-ah hydrogen gas 0.8 L/min pek a ni a, cathode-ah carbon dioxide 2 L/min pek a ni bawk. Anodic leh cathodic air stream pahnih hi 100% relative humidity leh 259 kPa absolute cathodic pressure-ah humidified a ni. Operation chhung hian cathode gas stream chu 1 M KOH solution nen 2 mL/min rate-in an pawlh a, hei hian cathode catalyst bed hman tangkai leh ionic conduction a tichak a ni. Anode gas stream pakhat chu deionized water nen 10 ml/min rate-in mix la, anode-a formic acid chu paih chhuak rawh. Device input leh output chungchang chipchiar takin Figure S5-ah hian tarlan a ni. Cathode exhaust gas hian CO2 a pai a, CO leh H2 a siam chhuak thin. Tui hnim chu condenser (2°C-a low temperature heat exchanger) hmangin lakchhuah a ni. Gas la awm chu gas timing analysis atan lakkhawm a ni ang. Anode flow pawh condenser kaltlangin liquid leh gas a then darh ang. Tui bawlhhlawh hi vial thianghlim takah lakkhawm a ni ang a, liquid chronometry hmangin formic acid siam chhuah zat tehna atan an zirchiang ang. Electrochemical test hi Garmy potentiostat (reference number 30K, Gamry, USA) hmangin an ti a. Polarization curve teh hmain cell chu linear voltammetry hmangin 0 atanga 250 mA/cm2 inkar ah vawi 4 condition a ni a, scan rate 2.5 mA/cm2 a ni. Polarization curve chu galvanostatic mode-ah siam a ni a, cell chu current density engemaw zatah minute 4 chhung dahin cathode gas leh anolyte liquid sample lak a ni.
MEA-ah hian hydrogen reference electrode hmangin cathode leh anodic potential te chu kan thliar hrang a. Reference electrode structure chu Figure S6a ah hian kan hmu a. MEA membrane leh reference electrode inzawmkhawmna atan Nafion membrane (Nafion 211, IonPower, USA) chu ionic bridge atan hman a ni. Nafion strip tawp khat chu 1 cm2 gas diffusion electrode (GDE) 0.25 mg Pt/cm2 (50 wt% Pt/C, TEC10E50E, TANAKA Precious Metals) loaded, 29BC carbon paper (Fuel Cell Store, USA)-a sputtered-ah an connect a. ). Special polyetheretherketone (PEEK) hardware hi GDE leh Nafion strip te gas seal leh inzawmna tha tak neih theihna tur leh reference electrode fuel cell hardware nena inzawm tir nan hman a ni. Nafion strip tawp dang chu CEM battery atanga chhuak chhuak nen a inzawm a ni. Figure S6b-ah hian MEA nena inzawm reference electrode cross section kan hmu a.
Exhaust gas chu condenser leh gas-liquid separator atanga a kal hnuah cathode atang hian gas sample lak a ni. Gas lakkhawm chu 4900 Micro GC (10 μm molecular sieve, Agilent) hmangin vawi thum tal an zirchiang a. Sample te hi inert multi-layer aluminum foil gas sample bag SupelTM (Sigma-Aldrich)-ah hun bituk (second 30) chhung lakkhawm niin, lakkhawm atanga darkar hnih chhungin microgas chromatograph-ah kut hmanga dah a ni. Injection temperature chu 110°C ah an dah a. Carbon monoxide (CO) leh hydrogen (H2) te chu carrier gas atan argon (Matheson Gas-Matheson Purity) hmangin heated (105 °C) pressurized (28 psi) 10 m MS5A column-ah an inthen a. Heng connection te hi a chhunga awm Thermal Conductivity Detector (TCD) hmanga hriat theih a ni. GC chromatogram leh CO leh H2 calibration curve te chu Figure S7 ah hian tarlan a ni. Anode atang hian liquid formic acid sample te chu hun bituk (second 120) chhung lakkhawm niin 0.22 μm PTFE syringe filter hmangin 2 mL vial ah filter a ni. Vial chhunga tui awmte chu Agilent 1260 Infinity II bioinert high-performance liquid chromatography (HPLC) system hmangin an zirchiang a, chutah chuan sample 20 μl chu autosampler (G5668A) hmangin mobile phase 4 mM sulfuric acid (H2SO4) hmangin an inject a ni. ) chu 0.6 ml/min (quaternary pump G5654A) a flow rate a ni. Products te chu Aminex HPX-87H 300 × 7.8 mm (Bio-Rad) lum (35°C, column oven G7116A)-ah Micro-Guard Cation H guard column hmaah an inthen a. Formic acid hi diode array detector (DAD) hmangin an hmuchhuak a. wavelength 210 nm leh bandwidth 4 nm-ah a awm. HPL chromatogram leh formic acid standard calibration curve te chu Figure S7-ah hian tarlan a ni.
Gas product (CO leh H2) FE te hi a hnuaia equation hmang hian chhut a ni a, gas mole zawng zawng chu ideal gas equation hmangin chhut a ni:
Chung zingah chuan: \({n}_{i}\): electrochemical reaction-a electron awm zat. \(F\): Faraday-a thil awm reng. \({C}_{i}\): HPLC tui atanga siam chhuah zat. \(V\): hun bituk chhunga liquid sample lakkhawm volume t. \(j\): tunlai density. \(A\): Electrode-a geometric area (25 cm2) a ni. \(t\): sample lak hun chhung. \(P\): pressure awmze nei tak. \({x}_{i}\): GC hmanga gas mole percentage teh. \(R\): gas awm reng. \(T\): boruak lum leh vawt.
Anodic cations concentration chu inductively coupled plasma atomic emission spectroscopy (ICP-OES) hmangin an chhut a ni. Anode chhunga leach emaw diffuse thei cations te chu Ti, Pt, Bi leh K te an ni a, K tih loh chu cations dang zawng zawng chu detection limit hnuaiah an awm vek a ni. Solution chhungah hian ion a siam a, anode chu proton emaw cations dang emaw nena pair turin a awmtir ta a ni. Chuvangin, formic acid thianghlimna chu hetiang hian chhut theih a ni
Formate/FA siamchhuah hian MEA configuration bik hmanga electric kWh khata FA siam chhuah zat a entir a, mol/kWh-in a tarlang a ni. Current density, cell voltage leh Faraday efficiency hmanga chhut a ni a, operating condition bik hnuaiah a ni.
Anode-a formic acid oxidized zat chu mass balance pum pui atanga chhut rawh. Cathode-ah hian reaction inelna pathum a awm a, chungte chu hydrogen evolution, CO2 chu CO-a tihtlem, leh CO2 chu formic acid-a tihtlem te an ni. Anton-ah hian formic acid oxidation process kan neih avangin formic acid FE hi hmun hnih ah then theih a ni a, chungte chu formic acid collection leh formic acid oxidation te an ni. Mass balance pum pui chu hetiang hian ziah theih a ni:
HPLC hmanga formic acid, hydrogen, leh CO khawlkhawm zat chhiar nan GC kan hmang a. Hriat tur chu formic acid tam zawk hi Supplementary Figure S5-a setup hmanga anode atanga lakkhawm a ni. Cathode chamber atanga formate lakkhawm zat hi a pawimawh lo hle a, order hnih velin a tlem a, SC zawng zawng atanga 0.5% aia tlem a ni.
Heta continuous transport model hman hi a hmaa system inang lo tak tak chungchanga hnathawh tawh atanga siam a ni34. Electronic leh ionic conducting phase-a tui concentration leh electrostatic potential hriat nan Poisson-Nerst-Planck (PNP) equation coupled system hman a ni. A hnuaia equation leh model geometry te chipchiar takin SI-ah hian tarlan a ni.
He system hian tui chhunga thil awm pariat (\({{{{{{\rm{C}}}}}}}{{{{{{\rm{O}}}}}}}}}_{2 \left ({{{{{{\rm{aq}}}}}\right)}\), \({{{{{{{\rm{H}}}}}}}}^{+ }\ ), \ ({{{{{{\rm{O}}}}}}{{{{{{{\rm{H}}}}}}^{-}\), \({{{ {{{ \rm{ HCO}}}}}}}}_{3}^{-}\), \({{{{{{{\rm{CO}}}}}}_{3}^{ 2-} \ ),\ ({{{{{\rm{HCOOH}}}}}}\), \({{{{{{{\rm{HCOO}}}}}}}}^{- }\) leh \({{{ {{{\rm{K}}}}}}^{+}\)), ionic conducting phase-a electrostatic potential (\({\phi }_{I}\ )) leh anodic leh cathodic electron conductivity te a awm bawk. Electrostatic potential chu phase hrang hrang (\({\phi }_{A}\) leh \({\phi }_{C}\) te a ni). Chu ai chuan local electrical neutrality emaw charge distribution function emaw pawh a takin a thleng lo va, space charge region chu Poisson-a equation hmangin direct-in a solve a Hetiang approach hmang hian CEM|AEM, CEM|Pore, leh AEM|Pore interface-ah Donnan repulsion effects direct-a model theih a ni. Tin, catalyst-a anodic leh cathodic layer-a charge transport sawifiahna atan porous electrode theory (PET) hman a ni bawk. A ziaktute hriat dan chuan he hnathawh hian space charge region tam tak nei system-a PET hman hmasak ber a entir a ni.
GDE BOT leh EOT cathode sample te chu Zeiss Xradia 800 Ultra 8.0 keV X-ray source nei, absorption leh wide field modes, leh image fusion1 hmanga test a ni. -90° atanga 90° thlenga thlalak 901 lakkhawm niin, exposure time chu second 50 a ni. Reconstruction chu back projection filter hmangin voxel size 64 nm hmangin an ti a. Segmentation leh particle size distribution thlirletna chu a bik taka ziah code hmangin an ti a.
Electron microscopic characterization ah hian test MEA te chu diamond knife hmanga ultrathin sectioning atana inbuatsaihna atan epoxy resin ah embed a ni. MEA tin cross section chu 50 atanga 75 nm a thuk thlengin an cut a. Talos F200X transmission electron microscope (Thermo Fisher Scientific) hmangin scanning transmission electron microscopy (STEM) leh energy-dispersive X-ray spectroscopy (EDS) hmanga tehna hman a ni. Microscope hi EDS Super-X system hmanga siam niin windowless SDD detector 4 a awm a, 200 kV-ah a thawk thei a ni.
Powder X-ray diffraction pattern (PXRD) chu Bruker Advance D8 powder X-ray diffractometer hmangin Ni-filtered Cu Kα radiation 40 kV leh 40 mA-a thawk hmangin an la a. Scanning range hi 10° atanga 60° thleng a ni a, step size hi 0.005° a ni a, data lakkhawmna speed hi step khatah second 1 a ni.
Bi2O3 Bi L3 catalyst sir lama RAS spectrum chu in lama siam cell hmangin potential function angin an teh a. Bi2O3 catalytic ionomer ink chu 26.1 mg Bi2O3 156.3 μL ionomer solution (6.68%) nena chawhpawlh hmangin 1 M KOH, tui (157 μL) leh isopropyl alcohol (104 μL) nena neutralized hmangin ionomer ink siam a ni. Catalyst coefficient chu 0.4 a ni. Ink chu graphene sheet-ah rectangular spot (10×4 mm)-ah Bi2O3 catalyst loading 0.5 mg/cm2 a thlen thlengin an hnawih a. Graphene sheet dang zawng chu Kapton hmanga khuh a ni a, chu chuan heng hmunte hi electrolyte atanga isolate a ni. Catalyst-coated graphene sheet chu PTFE pahnih inkarah dahin cell body (PEEK)-ah screw hmangin an nghet a, Figure S8. Hg/HgO (1 M NaOH) chu reference electrode atan a thawk a, carbon paper chu counter electrode atan a thawk bawk. Hg/HgO reference electrode chu hydrogen-saturated 0.1 M KOH-a thun platinum wire hmangin calibrate niin, potential tehna zawng zawng chu reversible hydrogen electrode (RHE) scale-ah a chantir a ni. XRD spectra chu 0.1 M KOH-a thun, 30 °C-a tihlum Bi2O3/graphene sheet working electrode potential enfiahna hmanga lak a ni. Electrolyte hi battery chhungah a inher kual a, electrolyte inlet chu cell hnuai lamah a awm a, outlet chu a chung lamah a awm a, hei hian bubble a lo awm hunah electrolyte chu catalyst layer nen a inzawm theih nan a ni. A hnathawhna electrode potential control nan CH Instruments 760e potentiostat hman a ni. Potential sequence chu open circuit potential a ni a: RHE a zirin -100, -200, -300, -400, -500, -800, -850, -900, -1000, -1100, -1500 leh +700 mV te a ni. iR potential zawng zawng chu siamrem vek a ni tawh.
Bi L3 edge (Bi metal tan ~13424 eV) X-ray absorption fine structure (XAFS) spectroscopy chu channel 10-ID, Advanced Photon Source (APS), Argonne National Fluorescence Laboratory-ah an ti a. Ram pum huapa Model tehna Laboratory-ah dah a ni. X-ray energy tune nan hian two-crystal Si(111) monochromator liquid nitrogen hmanga tihlum a ni a, rhodium-coated mirror hmangin harmonic content attenuate a ni. Scan energies chu 13200 atanga 14400 eV thleng a danglam a, fluorescence chu 5 × 5 silicon PIN diode array hmangin filter emaw Soller slits emaw awm lovin an teh a ni. Derivative pahnihna zero crossing energy chu Pt foil L2 edge kaltlangin 13271.90 eV-ah calibrate a ni. Electrochemical cell thickness avang hian reference standard spectrum chu a rualin teh theih a ni lo. Chutiang chuan, experiment chhung zawnga tehna nawn leh atanga chhut chuan incident X-ray energy-a scan-to-scan change chhut chu ±0.015 eV a ni. Bi2O3 layer thickness hian degree engemaw chen chu fluorescence self-absorption a thlen a; electrode te hian incident beam leh detector nena khaikhin chuan fixed orientation an vawng reng a, scan zawng zawng chu a inang vek vek a ni. Near-field XAFS spectrum hmangin bismuth oxidation state leh chemical form chu Athena software (version 0.9.26) linear combination fitting algorithm hmangin Bi leh Bi2O3 standard-a XANES region nena khaikhin a ni. code IFEFFIT hmangin 44 a ni.
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