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Ukwenziwa kwe-electrosynthesis ye-adipic acid (isandulela se-nylon 66) kusuka ku-oyela we-CA (ingxube ye-cyclohexanone ne-cyclohexanol) kuyisu elizinzile elingathatha indawo yezindlela zendabuko ezidinga izimo ezinzima. Kodwa-ke, ubuningi bamanje obuphansi kanye nokusabela kokuguquguquka komoya-mpilo okuncintisanayo kunciphisa kakhulu ukusetshenziswa kwayo kwezimboni. Kulo msebenzi, sishintsha i-nickel double hydroxide ne-vanadium ukuze sithuthukise ubuningi bamanje futhi sigcine ukusebenza kahle kwe-faradaic ephezulu (>80%) ngaphezu kobubanzi obukhona (1.5–1.9 V vs. i-hydrogen electrode eguquguqukayo). Izifundo zokuhlola nezethiyori zembule izindima ezimbili ezibalulekile zokuguqulwa kwe-V, okuhlanganisa ukwakhiwa kabusha kwe-catalyst okusheshayo kanye nokunyuswa kwe-cyclohexanone okuthuthukisiwe. Njengobufakazi bomqondo, sakha i-membrane-electrode assembly eyakhiqiza i-adipic acid esebenza kahle kakhulu kwe-faradaic (82%) kanye nokukhiqiza (1536 μmol cm-2 h-1) kubuningi bamanje obufanele izimboni (300 mA cm-2), ngenkathi sifinyelela ukuzinza >50 h. Lo msebenzi ubonisa isikhuthazo esisebenzayo sokwenza i-electrosynthesis ye-adipic acid ngokukhiqiza okuphezulu kanye namandla ezimboni.
I-Adipic acid (AA) ingenye yama-asidi e-aliphatic dicarboxylic abaluleke kakhulu futhi isetshenziswa kakhulu ekukhiqizweni kwe-nylon 66 kanye namanye ama-polyamides noma ama-polymer1. Ezimbonini, i-AA yenziwa ngokufaka i-oxidizing ingxube ye-cyclohexanol ne-cyclohexanone (okungukuthi, uwoyela we-AA) kusetshenziswa i-50–60 vol% nitric acid njenge-oxidizing agent. Le nqubo inezinkinga zemvelo ezihlobene nokukhishwa kwe-nitric acid egxilile kanye nama-nitrogen oxides (N2O kanye ne-NOx) njengegesi yokushisa i-greenhouse2,3. Nakuba i-H2O2 ingasetshenziswa njenge-ejenti yokufutha eluhlaza ehlukile, izindleko zayo eziphakeme kanye nezimo zokwenziwa kwayo ezinzima kwenza kube nzima ukuyisebenzisa ngokoqobo, futhi kudingeka indlela engabizi kakhulu neqhubekayo4,5,6.
Eminyakeni eyishumi edlule, izindlela zokwenziwa kwamakhemikhali nophethiloli nge-electrocatalytic zidonsele ukunaka okwandayo kososayensi ngenxa yezinzuzo zazo zokusebenzisa amandla avuselelekayo nokusebenza ngaphansi kwezimo ezithambile (isb., izinga lokushisa legumbi kanye nengcindezi ye-ambient)7,8,9,10. Kulokhu, ukuthuthukiswa kokuguqulwa kukawoyela we-KA nge-electrocatalytic kube yi-AA kubaluleke kakhulu ukuthola izinzuzo ezingenhla kanye nokuqeda ukusetshenziswa kwe-nitric acid kanye nokukhishwa kwe-nitrous oxide okutholakala ekukhiqizweni okuvamile (Isithombe 1a). Umsebenzi wokuphayona wenziwa nguPetrosyan et al., ababike ukuthi ukusabela kwe-electrocatalytic oxidation kwe-cyclohexanone (COR; cyclohexanone noma i-cyclohexanol kuye kwafundwa ngokuvamile njengokumelela uwoyela we-KA) ku-nickel oxyhydroxide (NiOOH), kodwa ukuminyana kwamanje okuphansi (6 mA cm-2) kanye nesivuno esimaphakathi se-AA (52%) kutholakale11,12. Kusukela ngaleso sikhathi, kuye kwenziwa intuthuko enkulu ekuthuthukisweni kwama-catalyst asekelwe ku-nickel ukuthuthukisa umsebenzi we-COR. Isibonelo, i-catalyst ye-nickel hydroxide (Cu-Ni(OH)2) ene-copper-doped yakhiwe ukuze ikhuthaze ukuhlukana kwe-Cα-Cβ ku-cyclohexanol13. Muva nje sibike nge-catalyst ye-Ni(OH)2 eguqulwe nge-sodium dodecyl sulfonate (SDS) ukuze kudalwe indawo encane engangenisi amanzi ecebisa i-cyclohexanone14.
a Izinselele zokukhiqizwa kwe-AA nge-electrooxidation kawoyela we-KA. b Ukuqhathaniswa kwe-COR ye-electrocatalytic yama-catalysts asekelwe ku-Ni abikwe ngaphambilini kanye ne-catalyst yethu ohlelweni lwe-electrode ezintathu kanye nohlelo lwebhethri lokugeleza11,13,14,16,26. Ulwazi oluningiliziwe ngamapharamitha okusabela kanye nokusebenza kokusabela lunikezwe kumaThebula Angeziwe 1 no-2. c Ukusebenza kwe-Catalytic kwama-catalysts ethu e-NiV-LDH-NS e-COR ku-reactor ye-H-cell kanye ne-MEA, asebenza ebangeni elibanzi lamandla.
Nakuba izindlela ezingenhla zithuthukise umsebenzi we-COR, ama-catalyst asekelwe ku-Ni achazwe abonise ukusebenza kahle kwe-AA Faraday okuphezulu (FE) (>80%) kuphela kuma-potentials aphansi kakhulu, ngokuvamile ngaphansi kuka-1.6 V uma kuqhathaniswa ne-hydrogen electrode eguquguqukayo (RHE, efingqiwe nge-VRHE). Ngakho-ke, i-partial current density ebikiwe (okungukuthi, i-total current density ephindaphindwe yi-FE) ye-AA ihlala ingaphansi kuka-60 mA cm−2 (Isithombe 1b kanye neThebula Elingeziwe 1). I-low current density ingaphansi kakhulu kwezidingo zezimboni (>200 mA cm−2)15, okuphazamisa kakhulu ubuchwepheshe be-electrocatalytic bokwenziwa kwe-high-throughput AA (Isithombe 1a; phezulu). Ukuze kwandiswe i-current density, i-potential enhle kakhulu (yohlelo lwe-three-electrode) noma i-voltage ephezulu yeseli (yohlelo lwe-two-electrode) ingasetshenziswa, okuyindlela elula yokuguqulwa okuningi kwe-electrocatalytic, ikakhulukazi i-oxygen evolution reaction (OER). Kodwa-ke, nge-COR kuma-anodic potentials aphezulu, i-OER ingaba umncintiswano omkhulu ekunciphiseni i-FE ye-AA, ngaleyo ndlela kuncishiswe ukusebenza kahle kwamandla (Isithombe 1a; phansi). Isibonelo, sibukeza inqubekela phambili yangaphambilini (Isithombe 1b kanye neThebula Elingeziwe 1), sidumele ukuthola ukuthi i-FE ye-AA ku-SDS-modified Ni(OH)2 yehle kusuka ku-93% kuya ku-76% ngokwandisa amandla asetshenziswayo kusuka ku-1.5 VRHE kuya ku-1.7 VRHE14, kuyilapho i-FE ye-AA ku-CuxNi1-x(OH)2/CF yehle kusuka ku-93% kuya ku-69% ngokwandisa amandla kusuka ku-1.52 VRHE kuya ku-1.62 VRHE16. Ngakho-ke, ukuminyana kwamanje okungaphelele okubikiwe kwe-AA akukhuphuki ngokulinganayo kuma-potentials aphezulu, okunciphisa kakhulu ukuthuthukiswa kokusebenza kwe-AA, ingasaphathwa eyokusetshenziswa kwamandla aphezulu ngenxa ye-FE ephansi ye-AA. Ngaphezu kwama-catalyst asekelwe ku-nickel, ama-catalyst asekelwe ku-cobalt nawo abonise umsebenzi we-catalytic ku-COR17,18,19. Kodwa-ke, ukusebenza kwawo kwehla ngamathuba aphezulu, futhi uma kuqhathaniswa nama-catalyst asekelwe ku-Ni, anemikhawulo eminingi engaba khona ekusetshenzisweni kwezimboni, njengokushintshashintsha kwamanani okukhulu kanye nempahla encane. Ngakho-ke, kuyafiseleka ukuthuthukisa ama-catalyst asekelwe ku-Ni ane-current density ephezulu kanye ne-FE ku-COR ukuze kube wusizo ukufeza isivuno esiphezulu se-AA.
Kulo msebenzi, sibika ama-nanosheet e-nickel aphindwe kabili e-nickel (NiV-LDH-NS) aguqulwe yi-vanadium(V) njengama-electrocatalyst asebenzayo ekukhiqizweni kwe-AA nge-COR, asebenza ngaphezu kobubanzi be-potential nge-OER ecindezelwe kakhulu, efinyelela i-FE ephezulu kanye nobuningi bamanje kokubili kumaseli e-H kanye nama-electrode e-membrane assemblies (MEAs; Umfanekiso 1 b). Okokuqala sibonisa ukuthi ukusebenza kahle kwe-acetylene oxidation ngaphezu kwe-catalyst ejwayelekile ye-Ni(OH)2 nanosheet (Ni(OH)2-NS) kwehla, njengoba kulindelekile, kuma-potential aphezulu, kusuka ku-80% ku-1.5 VRHE kuya ku-42% ku-1.9 VRHE. Ngokuphambene kakhulu, ngemuva kokushintsha i-Ni(OH)2 ne-V, i-NiV-LDH-NS ibonise ubuningi bamanje obuphezulu ku-potential ethile futhi, okubaluleke kakhulu, igcine i-FE ephezulu kububanzi be-potential. Isibonelo, ku-1.9 VRHE, ibonise ubuningi bamanje obungu-170 mA cm−2 kanye ne-FE engu-83%, okuyi-catalyst evumayo kakhulu ye-COR ohlelweni lwe-electrode ezintathu (Isithombe 1c kanye neThebula Elingeziwe 1). Idatha yokuhlola neyethiyori ikhombisa ukuthi ukuguqulwa kwe-V kukhuthaza i-kinetics yokunciphisa kusuka ku-Ni(OH)2 kuya kuma-oxyhydroxide e-Ni aphezulu (Ni3+xOOH1-x), asebenza njengesigaba esisebenzayo se-COR. Ngaphezu kwalokho, ukuguqulwa kwe-V kuthuthukise ukumuncwa kwe-cyclohexanone ebusweni be-catalyst, okudlale indima ebalulekile ekucindezeleni i-OER kuma-anodic potentials aphezulu. Ukuze sibonise amandla e-NiV-LDH-NS esimweni esingokoqobo, saklama i-MEA flow reactor futhi sabonisa i-FE ye-AA (82%) kubuningi bamanje obufanele imboni (300 mA cm−2), obuphakeme kakhulu kunemiphumela yethu yangaphambilini ku-membrane flow reactor (Isithombe 1b kanye neThebula Elingeziwe 2). Isivuno esihambisanayo se-AA (1536 μmol cm−2 h−1) sasiphezulu kakhulu kunalokho okutholakale kusetshenziswa inqubo ye-thermal catalytic (<30 mmol gcatalyst−1 h−1)4. Ngaphezu kwalokho, i-catalyst ibonise ukuzinza okuhle lapho kusetshenziswa i-MEA, igcina i-FE >80% AA amahora angama-60 ku-200 mA cm−2 kanye ne-FE >70% AA amahora angama-58 ku-300 mA cm−2. Ekugcineni, isifundo sokuqala sokusebenza (i-FEA) sibonise ukusebenza kahle kwesu le-electrocatalytic lokukhiqizwa kwe-AA.
Ngokusho kwezincwadi zangaphambilini, i-Ni(OH)2 iyi-catalyst ejwayelekile ekhombisa umsebenzi omuhle we-COR, ngakho-ke i-Ni(OH)2-NS13,14 yakhiwa okokuqala ngendlela ye-coprecipitation. Amasampula abonise isakhiwo se-β-Ni(OH)2, esaqinisekiswa yi-X-ray diffraction (XRD; Fig. 2a), kanye nama-nanosheet amancane kakhulu (ubukhulu: 2–3 nm, usayizi we-lateral: 20–50 nm) abonwe nge-high-resolution transmission electron microscopy (HRTEM; Supplementary Fig. 1) kanye nezilinganiso ze-atomic force microscopy (AFM) (Supplementary Fig. 2). Ukuhlanganiswa kwama-nanosheet nakho kwabonwa ngenxa yemvelo yawo emincane kakhulu.
amaphethini okusabalalisa kwe-X-ray e-Ni(OH)2-NS kanye ne-NiV-LDH-NS. I-FE, i-throughput, kanye ne-AA current density ku-b Ni(OH)2-NS kanye ne-c NiV-LDH-NS kuma-potential ahlukene. Amabha amaphutha amelela ukuphambuka okujwayelekile kwezilinganiso ezintathu ezizimele kusetshenziswa i-catalyst efanayo. d Isithombe se-HRTEM se-NV-LDH-NS. Ibha yesikali: 20 nm. Isithombe se-HAADF-STEM se-NiV-LDH-NS kanye nemephu ye-elemental ehambisanayo ekhombisa ukusatshalaliswa kwe-Ni (oluhlaza okotshani), i-V (ophuzi), kanye ne-O (oluhlaza okwesibhakabhaka). Ibha yesikali: 100 nm. f Ni 2p3/2, g O 1 s, kanye ne-h V 2p3/2 idatha ye-XPS ye-Ni(OH)2-NS (phezulu) kanye ne-NiV-LDH-NS (ngezansi). i-FE kanye ne-j yimisebenzi ye-AA kuma-catalyst amabili emijikelezweni engu-7. Amabha amaphutha amelela ukuphambuka okujwayelekile kwezilinganiso ezintathu ezizimele kusetshenziswa i-catalyst efanayo futhi angaphakathi kwe-10%. Idatha eluhlaza ye-a–c kanye ne-f–j inikezwa kumafayela edatha eluhlaza.
Sabe sesihlola umphumela we-Ni(OH)2-NS ku-COR. Sisebenzisa i-electrolysis eqhubekayo, sithole i-80% FE ye-AA ku-low potential (1.5 VRHE) ngaphandle kwe-OER (Isithombe 2b), okubonisa ukuthi i-COR ingcono kakhulu ngamandla kune-OER ku-low anodic potentials. Umkhiqizo oyinhloko olandelanayo utholakale ukuthi yi-glutaric acid (GA) ene-FE engu-3%. Ukuba khona kwamanani amancane e-succinic acid (SA), i-malonic acid (MA), kanye ne-oxalic acid (OA) nakho kwalinganiswa yi-HPLC (bheka Isibalo Esingeziwe 3 sokusatshalaliswa komkhiqizo). Akukho formic acid etholakele kumkhiqizo, okuphakamisa ukuthi i-carbonate ingase yakhiwe njengomkhiqizo olandelanayo we-C1. Ukuze kuhlolwe lo mbono, i-electrolyte evela ku-electrolysis ephelele ye-0.4 M cyclohexanone yafakwa i-acid futhi imikhiqizo yegesi yadlula ngesisombululo se-Ca(OH)2. Ngenxa yalokho, isisombululo saba yi-turbid, okuqinisekisa ukwakheka kwe-carbonate ngemuva kwe-electrolysis. Kodwa-ke, ngenxa kagesi ophansi okhiqizwa ngesikhathi senqubo ye-electrolysis (Isithombe 2b, c), ukuhlushwa kwe-carbonate kuphansi futhi kunzima ukukulinganisa. Ngaphezu kwalokho, eminye imikhiqizo ye-C2-C5 nayo ingakhiwa, kodwa inani layo alikwazi ukulinganiswa. Nakuba inani eliphelele lemikhiqizo kunzima ukulilinganisa, ama-90% e-electrochemical equivalent iyonke abonisa ukuthi iningi lezinqubo ze-electrochemical selitholiwe, okunikeza isisekelo sokuqonda kwethu kwemishini. Ngenxa yobuningi bamanje obuphansi (20 mA cm−2), isivuno se-AA sasingu-97 μmol cm−2 h−1 (Isithombe 2b), okulingana no-19 mmol h−1 g−1 ngokusekelwe ekuthwalweni okukhulu kwe-catalyst (5 mg cm−2), okuphansi kunokukhiqiza kwe-thermal catalytic (~30 mmol h−1 g−1)1. Lapho amandla asetshenziswayo enyuka kusuka ku-1.5 kuya ku-1.9 VRHE, yize ubuningi bamanje bukhuphuke (kusuka ku-20 kuya ku-114 mA cm−2), kwaba nokwehla okukhulu ngesikhathi esisodwa ku-AA FE, kusuka ku-80% kuya ku-42%. Ukwehla ku-FE kuma-potentials amahle kakhulu kungenxa yokuncintisana kwe-OER. Ikakhulukazi ku-1.7 VRHE, ukuncintisana kwe-OER kuholela ekwehleni okukhulu ku-AA FE, ngaleyo ndlela kunciphisa kancane ukusebenza kwe-AA ngokwanda kobuningi bamanje. Ngakho-ke, yize ubuningi bamanje obungaphelele be-AA bukhuphuke kusuka ku-16 kuya ku-48 mA cm−2 kanye nokukhiqiza kwe-AA kukhuphuke (kusuka ku-97 kuya ku-298 μmol cm−2 h−1), inani elikhulu lamandla engeziwe lasetshenziswa (2.5 W h gAA−1 ngaphezulu kusuka ku-1.5 kuya ku-1.9 VRHE), okwaholela ekwandeni kokukhishwa kwekhabhoni okungu-2.7 g CO2 gAA−1 (imininingwane yokubala inikezwe kuNothi Engeziwe 1). I-OER ephawulwe ngaphambilini njengomncintisani wokusabela kwe-COR kuma-anodic potentials aphezulu iyahambisana nemibiko yangaphambilini futhi imele inselele evamile yokuthuthukisa umkhiqizo we-AA14,17.
Ukuze sithuthukise i-catalyst ye-COR esekelwe ku-Ni(OH)2-NS esebenza kahle kakhulu, siqale sahlaziya isigaba esisebenzayo. Sibone iziqongo ku-473 cm-1 kanye no-553 cm-1 emiphumeleni yethu ye-in situ Raman spectroscopy (Isithombe Esingeziwe 4), esihambisana nokugoba nokwelula kwezibopho ze-Ni3+-O ku-NiOOH, ngokulandelana. Kuye kwabhalwa ukuthi i-NiOOH ingumphumela wokunciphisa kwe-Ni(OH)2 kanye nokuqongelela kwe-Ni(OH)O kuma-anodic potentials, futhi empeleni yisigaba esisebenzayo ku-electrocatalytic oxidation20,21. Ngakho-ke, silindele ukuthi ukusheshisa inqubo yokwakha kabusha isigaba se-Ni(OH)2 ku-NiOOH kungathuthukisa umsebenzi we-catalytic we-COR.
Sizame ukuguqula i-Ni(OH)2 ngezinsimbi ezahlukene njengoba kwaphawulwa ukuthi ukuguqulwa kwe-heteroatom kukhuthaza ukwakhiwa kabusha kwesigaba kuma-oxide/ama-hydroxide ensimbi aguqukayo angu-22,23,24. Amasampula akhiwe ngokufaka i-Ni kanye nesandulela sesibili sensimbi. Phakathi kwamasampula ahlukene aguqulwe ngensimbi, isampula eguquliwe engu-V (isilinganiso se-atomic esingu-V:Ni 1:8) (esibizwa ngokuthi i-NiV-LDH-NS) ibonise ubuningi bamanje obuphezulu ku-COR (Isithombe Esingeziwe 5) futhi okubaluleke kakhulu, i-AA FE ephezulu phezu kwefasitela elibanzi elinamandla. Ikakhulukazi, kumandla aphansi (1.5 VRHE), ubuningi bamanje be-NiV-LDH-NS babuphakeme ngokuphindwe ka-1.9 kunobe-Ni(OH)2-NS (39 vs. 20 mA cm−2), kanti i-AA FE yayifana kuzo zombili izihlungi (83% vs. 80%). Ngenxa yobuningi bamanje obuphezulu kanye ne-FE AA efanayo, umkhiqizo we-NiV-LDH-NS uphakeme ngokuphindwe ka-2.1 kunowe-Ni(OH)2-NS (204 vs. 97 μmol cm−2 h−1), okubonisa umphumela wokukhuthaza wokuguqulwa kwe-V kubuningi bamanje kuma-potentials aphansi (Isithombe 2c).
Ngokukhula kwamandla asetshenziswayo (isb., i-1.9 VRHE), ukuminyana kwamanje ku-NiV-LDH-NS kuphakeme ngokuphindwe ka-1.5 kunaku-Ni(OH)2-NS (170 vs. 114 mA cm−2), futhi ukwanda kufana nalokho okusemandleni aphansi (okuphindwe ka-1.9). Okuphawulekayo ukuthi i-NiV-LDH-NS igcine i-AA FE ephezulu (83%) kanti i-OER yacindezelwa kakhulu (O2 FE 4%; Umfanekiso 2c), idlula i-Ni(OH)2-NS kanye nama-catalyst abikwe ngaphambilini ane-AA FE ephansi kakhulu kuma-anodic potentials aphezulu (Ithebula Elingeziwe 1). Ngenxa ye-FE ephezulu ye-AA efasiteleni elibanzi elinamandla (1.5–1.9 VRHE), izinga lokukhiqizwa kwe-AA elingu-867 μmol cm−2 h−1 (elilingana no-174.3 mmol g−1 h−1) lafinyelelwa ku-1.9 VRHE, okubonisa ukusebenza okuhle ezinhlelweni ze-electrocatalytic ngisho ne-thermocatalytic lapho umsebenzi wenziwa waba ngokwejwayelekile ngokulayisha okuphelele kwesisindo samasampula e-NiV-LDH-NS (Isithombe Esingeziwe 6).
Ukuze siqonde ukuminyana kwamanje okuphezulu kanye ne-FE ephezulu phezu kobubanzi obukhona ngemuva kokushintsha i-Ni(OH)2 ne-V, sichaze isakhiwo se-NiV-LDH-NS. Imiphumela ye-XRD ibonise ukuthi ukuguqulwa nge-V kubangele ushintsho lwesigaba kusuka ku-β-Ni(OH)2 kuya ku-α-Ni(OH)2, futhi azikho izinhlobo zekristalu ezihlobene ne-V ezitholiwe (Isithombe 2a). Imiphumela ye-HRTEM ikhombisa ukuthi i-NiV-LDH-NS izuza i-morphology yama-nanosheet e-Ni(OH)2-NS amancane kakhulu futhi anobukhulu obufanayo obuseceleni (Isithombe 2d). Ukulinganiswa kwe-AFM kwembule ukuthambekela okunamandla kokuhlanganiswa kwama-nanosheet, okuholela ekujikeni okulinganiselwe okungaba ngu-7 nm (Isithombe Esingeziwe 7), esikhulu kune-Ni(OH)2-NS (ubukhulu: 2–3 nm). Ukuhlaziywa kwemephu ye-spectroscopy ye-X-ray ehlakazekayo (Isithombe 2e) kubonise ukuthi izakhi ze-V ne-Ni zazisatshalaliswe kahle kuma-nanosheet. Ukuze sicacise isakhiwo se-elekthronikhi se-V kanye nomphumela waso ku-Ni, sisebenzise i-X-ray photoelectron spectroscopy (XPS) (Isithombe 2f–h). I-Ni(OH)2-NS ibonise iziqongo ze-spin-orbit ezihlukile ze-Ni2+ (iqongo labesifazane ku-855.6 eV, iqongo lesathelayithi ku-861.1 eV, Isithombe 2f)25. I-O1 s XPS spectrum ye-Ni(OH)2-NS ingahlukaniswa ibe yiziqongo ezintathu, phakathi kwazo iziqongo ku-529.9, 530.9 kanye ne-532.8 eV zibangelwa yi-lattice oxygen (OL), i-hydroxyl group (Ni-OH) kanye ne-oxygen efakwe kuma-surface defects (OAds), ngokulandelana (Isithombe 2g)26,27,28,29. Ngemva kokuguqulwa nge-V, kwavela isiqongo se-V 2p3/2, esingahlukaniswa sibe yiziqongo ezintathu ezitholakala ku-517.1 eV (V5+), 516.6 eV (V4+) kanye no-515.8 eV (V3+), ngokulandelana, okubonisa ukuthi izinhlobo ze-V esakhiweni zikhona ikakhulukazi ezimweni ze-oxidation ephezulu (Isithombe 2h)25,30,31. Ngaphezu kwalokho, isiqongo se-Ni 2p ku-855.4 eV ku-NiV-LDH-NS sashintshwa kabi (cishe ngo-0.2 eV) uma kuqhathaniswa naleso esiku-Ni(OH)2-NS, okubonisa ukuthi ama-electron adluliselwe kusuka ku-V kuya ku-Ni. Isimo se-valence esiphansi kakhulu se-Ni esibonwe ngemuva kokuguqulwa kwe-V sasihambisana nemiphumela ye-Ni K-edge X-ray absorption near-edge spectroscopy (XANES) (bheka isigaba esithi “V Modification Promotes Catalyst Reduction” ngezansi ukuze uthole imininingwane eyengeziwe). I-NiV-LDH-NS ngemva kokwelashwa kwe-COR ihora eli-1 yabizwa ngokuthi i-NiV-LDH-POST futhi yachazwa ngokugcwele kusetshenziswa i-transmission electron microscopy, i-EDS mapping, i-X-ray diffraction, i-Raman spectroscopy, kanye nezilinganiso ze-XPS (Izithombe Ezingeziwe 8 no-9). Ama-catalyst ahlala njengama-aggregates ane-morphology ye-nanosheet encane kakhulu (Isithombe Esingeziwe 8a–c). Ukuqina kwamasampula kwehle kanti okuqukethwe kwe-V kwehle ngenxa ye-V leaching kanye nokwakhiwa kabusha kwe-catalyst (Isithombe Esingeziwe 8d–f). Ama-XPS spectra abonise ukwehla kokuqina kwe-V peak (Isithombe Esingeziwe 9), okwabangelwa yi-V leaching. Ngaphezu kwalokho, ukuhlaziywa kwe-spectrum ye-O1s (Umfanekiso Ongeziwe 9d) kanye nokulinganiswa kwe-electron paramagnetic resonance (EPR) (Umfanekiso Ongeziwe 10) kubonise ukuthi inani lezikhala ze-oxygen ku-NiV-LDH-NS landa ngemva kwehora eli-1 le-electrolysis, okungaholela ekushintsheni okungekuhle kwamandla okubopha e-Ni 2p (bheka Izithombe Ezingeziwe 9 no-10 ukuthola imininingwane eyengeziwe)26,27,32,33. Ngakho-ke, i-NiV-LDH-NS ibonise ushintsho oluncane lwesakhiwo ngemva kwehora eli-1 le-COR.
Ukuqinisekisa indima ebalulekile ye-V ekukhuthazeni i-COR, sakha ama-catalyst e-NiV-LDH anezilinganiso ezahlukene ze-atomic ze-V:Ni (1:32, 1:16, kanye no-1:4, ezibizwa ngokuthi i-NiV-32, i-NiV-16, kanye ne-NiV-4, ngokulandelana) ngaphandle kuka-1:8 ngendlela efanayo yokuhlanganisa. Imiphumela yemephu ye-EDS ikhombisa ukuthi isilinganiso se-atomic se-V:Ni ku-catalyst siseduze nesomlandeli (Isithombe Esingeziwe 11a–e). Ngokukhula kokuguqulwa kwe-V, amandla e-spectrum ye-V 2p ayanda, futhi amandla okubopha esifundeni se-Ni 2p aqhubeka nokushintshela ohlangothini olubi (Isithombe Esingeziwe 12). Ngesikhathi esifanayo, isilinganiso se-OL sanda kancane kancane. Imiphumela yokuhlolwa kwe-catalytic ikhombisa ukuthi i-OER ingacindezelwa ngempumelelo ngisho nangemva kokuguqulwa okuncane kwe-V (isilinganiso se-athomu se-V:Ni esingu-1:32), lapho i-O2 FE yehla kusuka ku-27% kuya ku-11% ku-1.8 VRHE ngemuva kokuguqulwa kwe-V (Isithombe Esingeziwe 11f). Ngokukhuphuka kwesilinganiso se-V:Ni kusuka ku-1:32 kuya ku-1:8, umsebenzi we-catalytic wanda. Kodwa-ke, ngokunyuka okuqhubekayo kokuguqulwa kwe-V (isilinganiso se-V:Ni esingu-1:4), ubuningi bamanje buyehla, esicabanga ukuthi kungenxa yokwehla kobuningi bezindawo ezisebenzayo ze-Ni (ikakhulukazi isigaba esisebenzayo se-NiOOH; Isithombe Esingeziwe 11f). Ngenxa yomphumela wokukhuthaza wokuguqulwa kwe-V kanye nokulondolozwa kwezindawo ezisebenzayo ze-Ni, i-catalyst enesilinganiso se-V:Ni esingu-1:8 ibonise ukusebenza okuphezulu kwe-FE kanye ne-AA ekuhlolweni kokuhlolwa kwesilinganiso se-V:Ni. Ukuze kucaciswe ukuthi isilinganiso se-V:Ni sihlala sinjalo ngemva kwe-electrolysis, ukwakheka kwama-catalyst asetshenzisiwe kwachazwa. Imiphumela ikhombisa ukuthi kuma-catalyst anezilinganiso zokuqala ze-V:Ni kusukela ku-1:16 kuya ku-1:4, isilinganiso se-V:Ni sehle saya cishe ku-1:22 ngemva kokusabela, okungaba ngenxa yokuphuma kwe-V ngenxa yokwakhiwa kabusha kwe-catalyst (Isithombe Esingeziwe 13). Qaphela ukuthi ama-AA FE afanayo abonwa lapho isilinganiso sokuqala se-V:Ni sasilingana noma siphakeme kune-1:16 (Isithombe Esingeziwe 11f), okungachazwa ngokwakhiwa kabusha kwe-catalyst okuholela ezilinganisweni ezifanayo ze-V:Ni kuma-catalyst abonisa ukusebenza okufanayo kwe-catalytic.
Ukuze siqinisekise ngokwengeziwe ukubaluleka kwe-V-modified Ni(OH)2 ekuthuthukiseni ukusebenza kwe-COR, sithuthukise ezinye izindlela ezimbili zokwenziwa ukuze singenise i-V ezintweni ze-Ni(OH)2-NS. Enye indlela yokuxuba, kanti isampula ibizwa ngokuthi i-NiV-MIX; enye indlela yokukhipha ama-sputtering ngokulandelana, kanti isampula ibizwa ngokuthi i-NiV-SP. Imininingwane yokwenziwa inikezwe esigabeni sezindlela. Ukumapha kwe-SEM-EDS kubonise ukuthi i-V iguqulwe ngempumelelo ebusweni be-Ni(OH)2-NS bamasampula womabili (Isithombe Esingeziwe 14). Imiphumela ye-electrolysis ikhombisa ukuthi ku-1.8 VRHE, ukusebenza kahle kwe-AA kuma-electrode e-NiV-MIX kanye ne-NiV-SP kungu-78% kanye no-79%, ngokulandelana, kokubili kubonisa ukusebenza kahle okuphezulu kune-Ni(OH)2-NS (51%). Ngaphezu kwalokho, i-OER kuma-electrode e-NiV-MIX kanye ne-NiV-SP yacindezelwa (FE O2: 7% kanye no-2%, ngokulandelana) uma kuqhathaniswa ne-Ni(OH)2-NS (FE O2: 27%). Le miphumela iqinisekisa umphumela omuhle wokuguqulwa kwe-V ku-Ni(OH)2 ekucindezelweni kwe-OER (Isithombe Esingeziwe 14). Kodwa-ke, ukuzinza kwama-catalyst kwaphazamiseka, okwabonakala ngokuncipha kwe-FE AA ku-NiV-MIX kuya ku-45% naku-NiV-SP kuya ku-35% ngemuva kwemijikelezo eyisikhombisa ye-COR, okusho isidingo sokwamukela izindlela ezifanele zokuzinzisa izinhlobo ze-V, njengokuguqulwa kwe-V ku-lattice ye-Ni(OH)2 ku-NiV-LDH-NS, okuyi-catalyst eyinhloko kulo msebenzi.
Siphinde sahlola ukuzinza kwe-Ni(OH)2-NS kanye ne-NiV-LDH-NS ngokufaka i-COR emijikelezweni eminingi. Ukusabela kwenziwa ihora eli-1 ngomjikelezo ngamunye futhi i-electrolyte yashintshwa ngemva komjikelezo ngamunye. Ngemva komjikelezo wesi-7, ukusebenza kwe-FE kanye ne-AA ku-Ni(OH)2-NS kwehle ngo-50% kanye no-60%, ngokulandelana, kuyilapho ukwanda kwe-OER kwabonwa (Isithombe 2i, j). Ngemva komjikelezo ngamunye, sihlaziye ama-curve e-cyclic voltammetry (CV) ama-catalyst futhi sabona ukuthi i-oxidation peak ye-Ni2+ yehla kancane kancane, okubonisa ukwehla kwamandla e-redox e-Ni (Isithombe Esingeziwe 15a–c). Kanye nokwanda kokuhlushwa kwe-Nication ku-electrolyte ngesikhathi se-electrolysis (Isithombe Esingeziwe 15d), sihlanganisa ukuwohloka kokusebenza (ukwehla kokukhiqiza kwe-FE kanye ne-AA) nokuphuma kwe-Ni kusuka ku-catalyst, okuholele ekuvezweni okukhulu kwe-substrate ene-foam ye-Ni ekhombisa umsebenzi we-OER. Ngokuphambene nalokho, i-NiV-LDH-NS yehlise ijubane lokwehla kokukhiqiza kwe-FE kanye ne-AA kwafika ku-10% (Isithombe 2i, j), okubonisa ukuthi ukuguqulwa kwe-V kuvimbele ngempumelelo i-Ni leaching (Isithombe Esingeziwe 15d). Ukuze siqonde ukuzinza okuthuthukisiwe kokuguqulwa kwe-V, senze izibalo zethiyori. Ngokusho kwezincwadi zangaphambilini34,35, ushintsho lwe-enthalpy lwenqubo yokususa insimbi yama-athomu ensimbi ebusweni obusebenzayo be-catalyst lungasetshenziswa njengesichazi esinengqondo sokuhlola ukuzinza kwe-catalyst. Ngakho-ke, izinguquko ze-enthalpy zenqubo yokususa insimbi yama-athomu e-Ni ebusweni (100) be-Ni(OH)2-NS eyakhiwe kabusha kanye ne-NiV-LDH-NS (i-NiOOH kanye ne-NiVOOH, ngokulandelana) zalinganiselwa (imininingwane yokwakhiwa kwemodeli ichazwe ku-Supplementary Note 2 kanye ne-Supplementary Fig. 16). Inqubo yokususa insimbi ye-Ni evela ku-NiOOH kanye ne-NiVOOH yaboniswa (Isithombe Esingeziwe 17). Izindleko zamandla zokususwa kwe-Ni ku-NiVOOH (0.0325 eV) ziphakeme kunezo ku-NiOOH (0.0005 eV), okubonisa ukuthi ukuguqulwa kwe-V kuthuthukisa ukuzinza kwe-NiOOH.
Ukuqinisekisa umphumela wokuvimbela i-OER ku-NiV-LDH-NS, ikakhulukazi kuma-anodic potentials aphezulu, kwenziwa i-differential electrochemical mass spectrometry (DEMS) ukuze kuhlolwe ukwakheka kwe-O2 okuxhomeke kumandla kumasampula ahlukene. Imiphumela ibonise ukuthi uma kungekho i-cyclohexanone, i-O2 ku-NiV-LDH-NS ivele kumandla okuqala angu-1.53 ​​VRHE, okwakuphansi kancane kune-O2 ku-Ni(OH)2-NS (1.62 VRHE) (Isithombe Esingeziwe 18). Lo mphumela uphakamisa ukuthi ukuvinjelwa kwe-OER kwe-NiV-LDH-NS ngesikhathi se-COR kungenzeka kungabi ngenxa yomsebenzi wayo we-OER ophansi, okuhambisana nobuningi bamanje obuphezulu kancane kuma-current sweep voltammetry (LSV) curves ku-NiV-LDH-NS kunalowo ku-Ni(OH)2-NS ngaphandle kwe-cyclohexanone (Isithombe Esingeziwe 19). Ngemva kokwethulwa kwe-cyclohexanone, ukuvela kwe-O2 okubambezelekile (mhlawumbe ngenxa yenzuzo ye-thermodynamic ye-COR) kuchaza i-FE ephezulu ye-AA esifundeni esinamandla aphansi. Okubaluleke kakhulu, amandla okuqala e-OER ku-NiV-LDH-NS (1.73 VRHE) abambezelekile kakhulu kunalawo aku-Ni(OH)2-NS (1.65 VRHE), okuhambisana ne-FE ephezulu ye-AA kanye ne-FE ephansi ye-O2 ku-NiV-LDH-NS kuma-potential amahle kakhulu (Isithombe 2c).
Ukuze siqonde kabanzi umphumela wokukhuthaza ukuguqulwa kwe-V, sihlaziye i-kinetics ye-OER kanye ne-COR reaction ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS ngokulinganisa imithambeka yazo ye-Tafel. Kubalulekile ukuqaphela ukuthi ubuningi bamanje esifundeni se-Tafel bubangelwa i-oxidation ye-Ni2+ kuya ku-Ni3+ ngesikhathi sokuhlolwa kwe-LSV kusukela ku-potential ephansi kuya ku-potential ephezulu. Ukuze sinciphise umphumela we-oxidation ye-Ni2+ ekulinganisweni kwe-COR Tafel slope, siqale safaka i-oxidation ku-1.8 VRHE imizuzu eyi-10 bese senza izivivinyo ze-LSV kwimodi yokuskena ebuyela emuva, okungukuthi, kusukela ku-potential ephezulu kuya ku-potential ephansi (Isithombe Esingeziwe 20). Ijika lokuqala le-LSV lalungiswa ngesinxephezelo se-100% iR ukuze kutholakale i-slope ye-Tafel. Uma kungekho i-cyclohexanone, i-Tafel slope ye-NiV-LDH-NS (41.6 mV dec−1) yayiphansi kuneye-Ni(OH)2-NS (65.5 mV dec−1), okubonisa ukuthi i-OER kinetics ingathuthukiswa ngokuguqulwa kwe-V (Isithombe Esingeziwe 20c). Ngemva kokwethulwa kwe-cyclohexanone, i-Tafel slope ye-NiV-LDH-NS (37.3 mV dec−1) yayiphansi kuneye-Ni(OH)2-NS (127.4 mV dec−1), okubonisa ukuthi ukuguqulwa kwe-V kwakunomphumela we-kinetic osobala kakhulu ku-COR uma kuqhathaniswa ne-OER (Isithombe Esingeziwe 20d). Le miphumela iphakamisa ukuthi yize ukuguqulwa kwe-V kukhuthaza i-OER ngezinga elithile, kusheshisa kakhulu i-COR kinetics, okuholela ekwandeni kwe-FE ye-AA.
Ukuze siqonde umphumela wokukhuthaza wokuguqulwa kwe-V okungenhla ekusebenzeni kwe-FE kanye ne-AA, sigxile ocwaningweni lwendlela yokusebenza. Eminye imibiko yangaphambilini ikhombisile ukuthi ukuguqulwa kwe-heteroatom kunganciphisa ukwakheka kwama-catalyst futhi kwandise indawo engaphezulu esebenza ngogesi (i-EAS), ngaleyo ndlela kwandise inani lezindawo ezisebenzayo futhi ngaleyo ndlela kuthuthukiswe umsebenzi we-catalytic36,37. Ukuze sihlole lokhu kungenzeka, senze izilinganiso ze-ECSA ngaphambi nangemva kokusebenza kwe-electrochemical, futhi imiphumela ikhombisile ukuthi i-ECSA ye-Ni(OH)2-NS kanye ne-NiV-LDH-NS yayifana (Isithombe Esingeziwe 21), ngaphandle kwethonya lobuningi bendawo esebenzayo ngemva kokuguqulwa kwe-V ekuthuthukisweni kwe-catalytic.
Ngokusho kolwazi olwamukelwa ngokuvamile, ku-electrooxidation ye-Ni(OH)2-catalyzed yama-alcohols noma ezinye i-nucleophilic substrates, i-Ni(OH)2 iqala ilahlekelwe ama-electron nama-proton bese yehliswa ibe yi-NiOOH ngezinyathelo ze-electrochemical ku-anodic potential ethile38,39,40,41. I-NiOOH eyakhiwe bese isebenza njengohlobo lwe-COR olusebenzayo lwangempela ukuze lukhiphe i-hydrogen nama-electron kusuka ku-nucleophilic substrate ngezinyathelo zamakhemikhali ukuze kwakheke umkhiqizo oxidized20,41. Kodwa-ke, muva nje kubikwe ukuthi yize ukwehliswa ku-NiOOH kungasebenza njengesinyathelo esinquma izinga (RDS) sokukhipha i-electrooxidation yotshwala ku-Ni(OH)2, njengoba kuphakanyiswe ezincwadini zakamuva, ukuxiliswa kwama-alcohols e-Ni3+ kungaba inqubo eyenzeka ngokuzenzakalelayo ngokudluliselwa kwama-electron angewona ama-redox ngokusebenzisa ama-orbital angenamuntu e-Ni3+41,42. Siphefumulelwe ucwaningo lwe-mechanistic olubikwe ezincwadini ezifanayo, sisebenzise i-dimethylglyoxime disodium salt octahydrate (C4H6N2Na2O2 8H2O) njenge-molecule ye-probe ukuze sibambe noma yikuphi ukwakheka kwe-Ni2+ okubangelwa ukunciphisa kwe-Ni3+ ngesikhathi se-COR (Isithombe Esingeziwe 22 kanye neNothi Engeziwe 3). Imiphumela ibonise ukwakheka kwe-Ni2+, okuqinisekisa ukuthi ukwehla kwamakhemikhali kwe-NiOOH kanye ne-electrooxidation ye-Ni(OH)2 kwenzeka ngesikhathi esisodwa ngesikhathi senqubo ye-COR. Ngakho-ke, umsebenzi we-catalytic ungancika kakhulu ku-kinetics yokunciphisa kwe-Ni(OH)2 ku-NiOOH. Ngokusekelwe kulesi simiso, siphenye ngokulandelayo ukuthi ukuguqulwa kwe-V kuzosheshisa ukwehla kwe-Ni(OH)2 futhi ngaleyo ndlela kuthuthukise i-COR.
Siqale sasebenzisa amasu e-in situ Raman ukukhombisa ukuthi i-NiOOH iyisigaba esisebenzayo se-COR ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS ngokubuka ukwakheka kwe-NiOOH kuma-potentials amahle kanye nokusetshenziswa kwayo okulandelayo ngemuva kokwethulwa kwe-cyclohexanone, kulandela inqubo "ye-electrochemical-chemical" eshiwo ngenhla (Isithombe 3a). Ngaphezu kwalokho, ukusabela kwe-NiV-LDH-NS eyakhiwe kabusha kudlule lokho kwe-Ni(OH)2-NS, njengoba kufakazelwa ukunyamalala okusheshayo kwesignali ye-Ni3+–O Raman. Sabe sesibonisa ukuthi i-NiV-LDH-NS ibonise amandla amancane okwakheka kwe-NiOOH uma kuqhathaniswa ne-Ni(OH)2-NS lapho kukhona noma kungekho khona i-cyclohexanone (Isithombe 3b, c kanye ne-Supplementary Fig. 4c, d). Okuphawulekayo ukuthi ukusebenza kwe-OER okuphezulu kwe-NiV-LDH-NS kuphumela kuma-bubble amaningi anamathela kulensi yangaphambili yenhloso yokulinganisa i-Raman, okubangela ukuthi isiqongo se-Raman ku-1.55 VRHE sinyamalale (Isifanekiso Esingeziwe 4d). Ngokusho kwemiphumela ye-DEMS (Isifanekiso Esingeziwe 18), ukuminyana kwamanje kuma-potentials aphansi (i-VRHE < 1.58 ye-Ni(OH)2-NS kanye ne-VRHE < 1.53 ye-NiV-LDH-NS) kungenxa yokwakhiwa kabusha kwama-ion e-Ni2+ kune-OER uma kungekho i-cyclohexanone. Ngakho-ke, isiqongo se-oxidation se-Ni2+ ku-LSV curve sinamandla kunese-NiV-LDH-NS, okubonisa ukuthi ukuguqulwa kwe-V kunikeza i-NiV-LDH-NS ikhono lokuvuselela elithuthukisiwe (bheka Isifanekiso Esingeziwe 19 ukuze uthole ukuhlaziywa okuningiliziwe).
a I-In situ Raman spectra ye-Ni(OH)2-NS (kwesobunxele) kanye ne-NiV-LDH-NS (kwesokudla) ngaphansi kwezimo ze-OCP ngemva kokushiswa kwe-preoxidation ku-1.5 VRHE ku-0.5 M KOH kanye ne-0.4 M cyclohexanone imizuzwana engu-60. b I-In situ Raman spectra ye-Ni(OH)2-NS kanye ne-c NiV-LDH-NS ku-0.5 M KOH + 0.4 M cyclohexanone kuma-potential ahlukene. d I-In situ XANES spectra ye-Ni(OH)2-NS kanye ne-NiV-LDH-NS ku-Ni K-edge ku-0.5 M KOH kanye ne-e 0.5 M KOH kanye ne-0.4 M cyclohexanone. I-inset ibonisa indawo ye-spectral ekhulisiwe phakathi kwe-8342 kanye ne-8446 eV. f I-Valence states ye-Ni ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS kuma-potential ahlukene. g I-In situ Ni EXAFS spectra ye-NiV-LDH-NS ngaphambi nangemva kokufakwa kwe-cyclohexanone kumandla ahlukene. h Amamodeli ethiyori e-Ni(OH)2-NS kanye ne-NiV-LDH-NS. Phezulu: Ku-Ni(OH)2-NS, ukuvuselelwa okuhamba kancane kusuka ku-Ni(OH)2-NS kuya ku-NiOOH kusebenza njenge-RDS, kuyilapho i-cyclohexanone yehlisa izinhlobo ze-Ni ezi-valent eziphezulu ngezinyathelo zamakhemikhali ukuze kugcinwe isimo se-Ni esi-valent esiphansi ukuze kukhiqizwe i-AA. Ngezansi: Ku-NiV-LDH-NS, isinyathelo sokuvuselela senziwa lula ukuguqulwa kwe-V, okuholela ekudluliselweni kwe-RDS kusuka esinyathelweni sokuvuselela kuya esinyathelweni samakhemikhali. i Izinguquko zamandla amahhala e-Gibbs lapho kwakhiwa kabusha i-Ni(OH)2-NS kanye ne-NiV-LDH-NS. Idatha eluhlaza ye-aj kanye ne-i inikezwe kufayela ledatha eluhlaza.
Ukuze sihlole ukuvela kwezakhiwo ze-athomu neze-elekthronikhi ngesikhathi sokunciphisa i-catalyst, senze izivivinyo ze-X-ray absorption spectroscopy (XAS) endaweni, ezinikeze ithuluzi elinamandla lokuphenya ukuguquguquka kwezinhlobo ze-Ni ngezinyathelo ezintathu ezilandelanayo: i-OER, i-cyclohexanone injection, kanye ne-COR at open circuit potential (OCP). Lesi sibalo sibonisa i-K-edge XANES spectra ye-Ni enekhono elikhulayo ngaphambi nangemva kwe-cyclohexanone injection (Isithombe 3d, e). Ngesikhathi esifanayo, amandla onqenqema lokumunca we-NiV-LDH-NS amahle kakhulu kunalawo e-Ni(OH)2-NS (Isithombe 3d, e, inset). I-valence emaphakathi ye-Ni ngaphansi kwesimo ngasinye ilinganiswe ngokulingana okuhlanganisiwe kwe-XANES spectra kanye nokubuyela emuva kwe-Ni K-edge absorption energy shift (Isithombe 3f), nge-reference spectrum ethathwe ezincwadini ezishicilelwe (Isithombe Esingeziwe 23)43.
Esinyathelweni sokuqala (ngaphambi kokwethulwa kwe-cyclohexanone, okuhambisana nenqubo ye-OER; Isithombe 3f, kwesobunxele), emandleni e-catalyst engakakhiwa kabusha (<1.3 VRHE), isimo se-valence se-Ni ku-NiV-LDH-NS (+1.83) siphansi kancane kunese-Ni(OH)2-NS (+1.97), esingabangelwa ukudluliselwa kwe-electron kusuka ku-V kuya ku-Ni, okuhambisana nemiphumela ye-XPS eshiwo ngenhla (Isithombe 2f). Lapho amandla edlula iphuzu lokunciphisa (1.5 VRHE), isimo se-valence se-Ni ku-NiV-LDH-NS (+3.28) sibonisa ukwanda okusobala kakhulu uma kuqhathaniswa nese-Ni(OH)2-NS (+2.49). Emandleni aphezulu (1.8 VRHE), isimo se-valence sezinhlayiya ze-Ni esitholwe ku-NiV-LDH-NS (+3.64) siphakeme kunese-Ni(OH)2-NS (+3.47). Ngokusho kwemibiko yakamuva, le nqubo ihambisana nokwakheka kwezinhlobo ze-Ni4+ ezi-valent ephezulu esakhiweni se-Ni3+xOOH1-x (i-Ni3+x uhlobo oluxubile lwe-Ni3+ kanye ne-Ni4+), oluye lwabonisa umsebenzi othuthukisiwe we-catalytic ekukhishweni kwe-alcohol38,39,44. Ngakho-ke, ukusebenza okuphezulu kwe-NiV-LDH-NS ku-COR kungase kube ngenxa yokunciphisa okuthuthukisiwe ukwakha izinhlobo ze-Ni ezi-valent eziphezulu ezisebenza nge-catalytically.
Esinyathelweni sesibili (ukwethulwa kwe-cyclohexanone ngemva kokuvulwa kwendandatho, Umfanekiso 3f), isimo se-valence se-Ni kuzo zombili izihlungi sehle kakhulu, okuhambisana nenqubo yokunciphisa i-Ni3+xOOH1-x nge-cyclohexanone, ehambisana nemiphumela ye-in situ Raman spectroscopy (Umfanekiso 3a), kanye nesimo se-valence se-Ni cishe sabuyela esimweni sokuqala (isinyathelo sokuqala ngamandla aphansi), okubonisa ukuguquguquka kwenqubo ye-redox ye-Ni kuya ku-Ni3+xOOH1-x.
Esinyathelweni sesithathu (inqubo ye-COR) kuma-COR potentials (1.5 kanye no-1.8 VRHE; Isithombe 3f, kwesokudla), isimo se-valence se-Ni ku-Ni(OH)2-NS sikhuphuke kancane kuphela (+2.16 kanye no-+2.40), okuphansi kakhulu kunasesimeni esifanayo esinyathelweni sokuqala (+2.49 kanye no-+3.47). Le miphumela ikhombisa ukuthi ngemva kokujova kwe-cyclohexanone, i-COR inqunyelwe ngokwe-kinetically yi-oxidation ehamba kancane ye-Ni2+ ku-Ni3+x (okungukuthi, ukwakhiwa kabusha kwe-Ni) kunokuba kube yisinyathelo samakhemikhali phakathi kwe-NiOOH kanye ne-cyclohexanone ku-Ni(OH)2-NS, okushiya i-Ni esimweni se-valence esiphansi. Ngakho-ke, siphetha ngokuthi ukwakhiwa kabusha kwe-Ni kungasebenza njenge-RDS enqubweni ye-COR ku-Ni(OH)2-NS. Ngokuphambene nalokho, i-NiV-LDH-NS igcine i-valence ephezulu kakhulu yezinhlobo ze-Ni (>3) ngesikhathi senqubo ye-COR, kanti i-valence yehle kancane kakhulu (ngaphansi kuka-0.2) uma kuqhathaniswa nesinyathelo sokuqala nge-potential efanayo (1.65 kanye ne-1.8 VRHE), okubonisa ukuthi ukuguqulwa kwe-V kukhuthaze ngokwe-kinetically i-oxidation ye-Ni2+ ibe yi-Ni3+x, okwenza inqubo yokunciphisa i-Ni isheshe kunesinyathelo samakhemikhali sokunciphisa i-cyclohexanone. Imiphumela ye-extended X-ray absorption fine structure (EXAFS) iphinde yembule ukuguqulwa okuphelele kwezibopho ze-Ni-O (kusukela ku-1.6 kuya ku-1.4 Å) kanye ne-Ni-Ni(V) (kusukela ku-2.8 kuya ku-2.4 Å) lapho kukhona i-cyclohexanone. Lokhu kuhambisana nokwakhiwa kabusha kwesigaba se-Ni(OH)2 kuya esigabeni se-NiOOH kanye nokunciphisa kwamakhemikhali kwesigaba se-NiOOH nge-cyclohexanone (Isithombe 3g). Kodwa-ke, i-cyclohexanone yaphazamisa kakhulu i-kinetics yokunciphisa i-Ni(OH)2-NS (bheka i-Supplementary Note 4 kanye ne-Supplementary Fig. 24 ukuthola imininingwane eyengeziwe).
Sekukonke, ku-Ni(OH)2-NS (Isithombe 3h, phezulu), isinyathelo sokunciphisa kancane kusuka esigabeni se-Ni(OH)2 kuya esigabeni se-NiOOH singasebenza njenge-RDS yenqubo yonke ye-COR kunesinyathelo samakhemikhali sokwakheka kwe-AA kusuka ku-cyclohexanone ngesikhathi sokunciphisa kwamakhemikhali kwe-NiOOH. Ku-NiV-LDH-NS (Isithombe 3h, phansi), ukuguqulwa kwe-V kuthuthukisa i-oxidation kinetics ye-Ni2+ kuya ku-Ni3+x, ngaleyo ndlela kusheshiswe ukwakheka kwe-NiVOOH (esikhundleni sokusetshenziswa ngokunciphisa kwamakhemikhali), okushintsha i-RDS iye esinyathelweni samakhemikhali. Ukuze siqonde ukwakhiwa kabusha kwe-Ni okubangelwa ukuguqulwa kwe-V, senze izibalo ezengeziwe zethiyori. Njengoba kuboniswe ku-Fig. 3h, silingise inqubo yokwakha kabusha ye-Ni(OH)2-NS kanye ne-NiV-LDH-NS. Amaqembu e-lattice hydroxyl ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS asuswa ngokukhipha i-OH- ku-electrolyte ukuze kwakhiwe i-lattice oxygen engenama-electron. Ukusabela kwamakhemikhali okuhambisanayo kungokulandelayo:
Ushintsho lwamandla angenama-Gibbs lokwakhiwa kabusha lubalwe (Isithombe 3i), kanti i-NiV-LDH-NS (0.81 eV) ibonise ushintsho lwamandla angenama-Gibbs oluncane kakhulu kune-Ni(OH)2-NS (1.66 eV), okubonisa ukuthi ukuguqulwa kwe-V kunciphisa i-voltage edingekayo yokwakha kabusha i-Ni. Sikholelwa ukuthi ukukhuthaza ukwakha kabusha kunganciphisa isithiyo samandla se-COR yonke (bheka isifundo sendlela yokusabela ngezansi ukuthola imininingwane), ngaleyo ndlela kusheshiswe ukusabela ekuminyaneni kwamanje okuphezulu.
Ukuhlaziywa okungenhla kukhombisa ukuthi ukuguqulwa kwe-V kubangela ukuhlelwa kabusha kwesigaba okusheshayo kwe-Ni(OH)2, ngaleyo ndlela kwandise izinga lokusabela kanye, futhi, ubuningi bamanje be-COR. Kodwa-ke, izindawo ze-Ni3+x zingakhuthaza nomsebenzi we-OER. Kusukela ku-LSV curve ngaphandle kwe-cyclohexanone, kusobala ukuthi ubuningi bamanje be-NiV-LDH-NS buphakeme kunobe-Ni(OH)2-NS (Isithombe Esingeziwe 19), okubangela ukusabela kwe-COR kanye ne-OER ukuthi kwakheke ukusabela okuncintisanayo. Ngakho-ke, i-FE ephezulu kakhulu ye-AA kuneye-NiV-LDH-NS ayikwazi ukuchazwa ngokugcwele ukuguqulwa kwe-V okukhuthaza ukuhlelwa kabusha kwesigaba.
Kuyavunywa ngokuvamile ukuthi ku-alkaline media, ukusabela kwe-electrooxidation kwe-substrates ze-nucleophilic kuvame ukulandela imodeli ye-Langmuir-Hinshelwood (LH). Ngokukhethekile, i-substrate kanye ne-OH− anions kuhlanganiswa ngokuncintisana ebusweni be-catalyst, futhi i-OH− efakwe i-oxidized ifakwa kumaqembu e-hydroxyl asebenzayo (OH*), asebenza njenge-electrophiles ukuze kufakwe i-oxidation yama-nucleophiles, indlela eye yaboniswa ngaphambilini ngedatha yokuhlola kanye/noma izibalo zethiyori45,46,47. Ngakho-ke, ukuhlushwa kwama-reactants kanye nesilinganiso sawo (i-organic substrate kanye ne-OH−) kungalawula ukumbozwa kwe-reactant kwendawo ye-catalyst, ngaleyo ndlela kuthinte i-FE kanye nesivuno somkhiqizo oqondiwe14,48,49,50. Esimweni sethu, sicabanga ukuthi ukumbozwa okuphezulu kwe-cyclohexanone ku-NiV-LDH-NS kuthanda inqubo ye-COR, futhi ngokuphambene nalokho, ukumbozwa okuphansi kwe-cyclohexanone ku-Ni(OH)2-NS kuthanda inqubo ye-OER.
Ukuze sihlole umbono ongenhla, siqale senza uchungechunge olubili lwezivivinyo ezihlobene nokuhlushwa kwama-reactants (C, cyclohexanone, kanye ne-COH−). Ukuhlolwa kokuqala kwenziwa nge-electrolysis ku-constant potential (1.8 VRHE) kuma-catalyst e-Ni(OH)2-NS kanye ne-NiV-LDH-NS anokuqukethwe okuhlukile kwe-cyclohexanone C (0.05 ~ 0.45 M) kanye nokuqukethwe okuhleliwe kwe-COH− (0.5 M). Ngemuva kwalokho, kwabalwa umkhiqizo we-FE kanye ne-AA. Kwi-catalyst ye-NiV-LDH-NS, ubudlelwano phakathi kwe-AA yield kanye ne-cyclohexanone C bubonise ijika elijwayelekile "lohlobo lwentaba-mlilo" kumodi ye-LH (Isithombe 4a), okubonisa ukuthi ukumbozwa okuphezulu kwe-cyclohexanone kuncintisana ne-OH− adsorption. Ngenkathi ku-Ni(OH)2-NS, isivuno se-AA sanda ngendlela efanayo ngokunyuka kwe-C ye-cyclohexanone kusuka ku-0.05 kuya ku-0.45 M, okubonisa ukuthi yize ukugcwala okukhulu kwe-cyclohexanone kwakuphezulu (0.45 M), ukumbozwa kwayo kwakusephansi kakhulu. Ngaphezu kwalokho, ngokukhuphuka kwe-COH− kuya ku-1.5 M, ijika "lohlobo lwentaba-mlilo" labonwa ku-Ni(OH)2-NS kuye nge-C ye-cyclohexanone, futhi iphuzu lokushintsha kokusebenza labambezeleka uma liqhathaniswa ne-NiV-LDH-NS, okufakazela ngokwengeziwe ukumuncwa okubuthakathaka kwe-cyclohexanone ku-Ni(OH)2-NS (Isithombe Esingeziwe 25a kanye neNothi 5). Ngaphezu kwalokho, i-FE ye-AA ku-NiV-LDH-NS yayizwela kakhulu ku-C-cyclohexanone futhi yanda ngokushesha yafinyelela ngaphezu kuka-80% lapho i-C-cyclohexanone inyuswa kusuka ku-0.05 M kuya ku-0.3 M, okubonisa ukuthi i-cyclohexanone yayinothe kalula ku-NiV-LDH-NS (Isithombe 4b). Ngokuphambene nalokho, ukwandisa ukuhlushwa kwe-C-cyclohexanone akuzange kuvimbele kakhulu i-OER ku-Ni(OH)2-NS, okungenzeka ukuthi kungenxa yokungangeneli kokumuncwa kwe-cyclohexanone. Ngokuphambene nalokho, uphenyo olwengeziwe lokuncika kwe-COH− ekusebenzeni kahle kwe-catalytic luphinde lwaqinisekisa ukuthi ukumuncwa kwe-cyclohexanone kuthuthukisiwe uma kuqhathaniswa ne-NiV-LDH-NS, engabekezelela i-COH− ephezulu ngesikhathi senqubo ye-COR ngaphandle kokunciphisa i-FE ye-AA (Isithombe Esingeziwe 25b, c kanye neNothi 5).
Ukukhiqiza kwe-AA kanye ne-EF ye-b Ni(OH)2-NS kanye ne-NiV-LDH-NS ku-cyclohexanone ene-C ehlukile ku-0.5 M KOH. c Amandla okumunca e-cyclohexanone ku-NiOOH kanye ne-NiVOOH. d I-FE ye-AA ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS ku-0.5 M KOH kanye ne-0.4 M cyclohexanone ku-1.80 VRHE kusetshenziswa amasu angakwazi ukuqhubeka futhi ahlala njalo. Amabha amaphutha amelela ukuphambuka okujwayelekile kwezilinganiso ezintathu ezizimele kusetshenziswa isampula efanayo futhi angaphakathi kuka-10%. e Phezulu: Ku-Ni(OH)2-NS, i-cyclohexanone enendawo ephansi yobuso C imuncwa kancane yi-cyclohexanone, okuholela ekuncintisaneni okunamandla kwe-OER. Ngezansi: Ku-NiV-LDH-NS, ukugcwala okuphezulu kwe-cyclohexanone C endaweni yobuso kubonakala ngomuncwa owandisiwe we-cyclohexanone, okuholela ekucindezelweni kwe-OER. Idatha eluhlaza ye-a–d inikezwa kufayela ledatha eluhlaza.
Ukuze sihlole ukumuncwa okuthuthukisiwe kwe-cyclohexanone ku-NiV-LDH-NS, sisebenzise i-electrochemical coupled quartz crystal microbalance (E-QCM) ukuqapha ushintsho olukhulu lwezinhlobo ezimuncwa ngesikhathi sangempela. Imiphumela ibonise ukuthi amandla okuqala okumuncwa kwe-cyclohexanone ku-NiV-LDH-NS ayekhulu ngokuphindwe ka-1.6 kunalawo aku-Ni(OH)2-NS esimweni se-OCP, futhi lo mehluko emandleni okumuncwa wanda kakhulu njengoba amandla enyuka afinyelela ku-1.5 VRHE (Isithombe Esingeziwe 26). Izibalo ze-DFT ezi-spin-polarized zenziwa ukuze kuhlolwe ukuziphatha kokumuncwa kwe-cyclohexanone ku-NiOOH naku-NiVOOH (Isithombe 4c). I-Cyclohexanone inamathela ku-Ni-center ku-NiOOH ngamandla okunamathela (ama-Ead) angu--0.57 eV, kuyilapho i-cyclohexanone inganamathela ku-Ni-center noma ku-V-center ku-NiVOOH, lapho i-V-center inikeza ama-Eads aphansi kakhulu (-0.69 eV), okuhambisana nokunamathela okunamandla okubonwe kwe-cyclohexanone ku-NiVOOH.
Ukuze siqinisekise ngokwengeziwe ukuthi ukumuncwa okuthuthukisiwe kwe-cyclohexanone kungakhuthaza ukwakheka kwe-AA futhi kuvimbele i-OER, sisebenzise isu le-discontinuous potential lokucebisa i-cyclohexanone ebusweni be-catalyst (ye-Ni(OH)2-NS kanye ne-NiV-LDH-NS), okwaphefumulelwa yimibiko yangaphambilini. 51, 52 Ngokuqondile, sisebenzise i-potential engu-1.8 VRHE ku-COR, sabe sesiyishintshela esimweni se-OCP, sabe sesiyishintshela emuva ku-1.8 VRHE. Kulesi simo, i-cyclohexanone ingaqongelela ebusweni be-catalyst esimweni se-OCP phakathi kwama-electrolyses (bheka isigaba se-Methods ukuze uthole izinqubo eziningiliziwe). Imiphumela ibonise ukuthi kwi-Ni(OH)2-NS kanye ne-NiV-LDH-NS, ukusebenzisa i-discontinuous potential electrolysis kuthuthukise ukusebenza kwe-catalytic uma kuqhathaniswa ne-constant potential electrolysis (Isithombe 4d). Okuphawulekayo ukuthi i-Ni(OH)2-NS ibonise ukuthuthuka okuphawulekayo ku-COR (AA FE: kusuka ku-51% kuya ku-82%) kanye nokucindezelwa kwe-OER (O2 FE: kusuka ku-27% kuya ku-4%) kune-NiV-LDH-NS, okwabangelwa iqiniso lokuthi ukuqongelela kwe-cyclohexanone kungathuthukiswa ngezinga elikhulu ku-catalyst enekhono elibuthakathaka lokumunca (okungukuthi, i-Ni(OH)2-NS) nge-electrolysis engaba khona ngezikhathi ezithile.
Sekukonke, ukuvinjelwa kwe-OER ku-NiV-LDH-NS kungabangelwa ukumuncwa okuthuthukisiwe kwe-cyclohexanone (Isithombe 4e). Ku-Ni(OH)2-NS (Isithombe 4e, phezulu), ukumuncwa okubuthakathaka kwe-cyclohexanone kuholele ekumbozweni kwe-cyclohexanone okuphansi kanye nokumbozwa kwe-OH* okuphezulu ebusweni be-catalyst. Ngakho-ke, izinhlobo ze-OH* ezengeziwe zizoholela ekuncintisaneni okukhulu kwe-OER futhi zinciphise i-FE ye-AA. Ngokuphambene nalokho, ku-NiV-LDH-NS (Isithombe 4e, phansi), ukuguqulwa kwe-V kwandise amandla okumuncwa kwe-cyclohexanone, ngaleyo ndlela kwandise ubuso be-C be-cyclohexanone futhi kwasebenzisa ngempumelelo izinhlobo ze-OH* ezimuncwayo ze-COR, kwakhuthaza ukwakheka kwe-AA futhi kwavimbela i-OER.
Ngaphezu kokuphenya ngomphumela wokuguqulwa kwe-V ekwakhiweni kabusha kwezinhlobo ze-Ni kanye nokumuncwa kwe-cyclohexanone, siphinde sahlola ukuthi i-V iyawushintsha yini umzila wokwakheka kwe-AA kusuka ku-COR. Kuye kwaphakanyiswa izindlela eziningana ezahlukene ze-COR ezincwadini, futhi sihlaziye amathuba azo ohlelweni lwethu lokusabela (bheka i-Supplementary Fig. 27 kanye ne-Supplementary Note 6 ukuthola imininingwane eyengeziwe)13,14,26. Okokuqala, kubikwe ukuthi isinyathelo sokuqala sendlela ye-COR singase sihilele ukucutshungulwa kokuqala kwe-cyclohexanone ukuze kwakheke i-key intermediate 2-hydroxycyclohexanone (2)13,14. Ukuze siqinisekise inqubo, sisebenzise i-5,5-dimethyl-1-pyrrolidine N-oxide (DMPO) ukuze sibambe ama-intermediate asebenzayo afakwe ebusweni be-catalyst futhi safunda i-EPR. Imiphumela ye-EPR iveze ukuba khona kwama-radicals agxile ku-C (R) kanye nama-radicals e-hydroxyl (OH) kuzo zombili izikhuthazi ngesikhathi senqubo ye-COR, okubonisa ukuthi ukukhishwa kwe-Cα − H kwe-cyclohexanone kwakha i-radical ephakathi nendawo (1), ephinde i-oxidized yi-OH* ukuze yakhe u-2 (Isithombe 5a kanye nesithombe esengeziwe 28). Nakuba izikhuthazi ezifanayo zitholakale kuzo zombili izikhuthazizi, ingxenye yendawo yesignali ye-R ku-NiV-LDH-NS yayiphakeme kakhulu kuneye-Ni(OH)2-NS, okungenzeka ukuthi ibangelwa amandla okufakwa kwe-cyclohexanone athuthukisiwe (Ithebula Elingeziwe 3 kanye neNothi 7). Siphinde sasebenzisa u-2 no-1,2-cyclohexanedione (3) njengezinto zokuqala ezisabelayo ze-electrolysis ukuhlola ukuthi i-V izoyishintsha yini isinyathelo esilandelayo se-oxidation. Imiphumela ye-electrolysis yama-intermediate angaba khona (2 no-3) ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS ibonise ukukhethwa komkhiqizo okufanayo, okubonisa ukuthi ukusabela kwe-COR ku-Ni(OH)2-NS noma i-NiV-LDH-NS kwaqhubeka ngezindlela ezifanayo (Isithombe 5b). Ngaphezu kwalokho, i-AA yayingumkhiqizo oyinhloko kuphela lapho u-2 esetshenziswa njenge-reactant, okuphakamisa ukuthi i-AA itholakale ngenqubo yoku-oxidation eqondile ngokuqhekeka kwesibopho se-Cα − Cβ esingu-2 esikhundleni soku-oxidation okulandelayo ku-3 kuzo zombili izi-catalyst, njengoba yaguqulwa kakhulu yaba yi-GA lapho u-3 esetshenziswa njenge-reactant yokuqala (Izibalo Ezingeziwe 29, 30).
Isignali ye-EPR ye-NiV-LDH-NS ku-0.5 M KOH + 0.4 M cyclohexanone. b Imiphumela yokuhlaziywa kwe-electrocatalytic kwe-2-hydroxycyclohexanone (2) kanye ne-1,2-cyclohexanedione (3). I-Electrolysis yenziwe ku-0.5 M KOH kanye no-0.1 M 2 noma 3 ku-1.8 VRE ihora elilodwa. Amabha amaphutha amelela ukuphambuka okujwayelekile kwezilinganiso ezimbili ezizimele kusetshenziswa i-catalyst efanayo. c Izindlela zokusabela eziphakanyisiwe ze-COR kuma-catalyst amabili. d Umfanekiso weskimu wendlela ye-COR ku-Ni(OH)2-NS (kwesobunxele) kanye no-d NiV-LDH-NS (kwesokudla). Imicibisholo ebomvu ikhombisa izinyathelo ezikhuthazwa ukuguqulwa kwe-V enqubweni ye-COR. Idatha eluhlaza ye-a kanye ne-b inikezwa kufayela ledatha eluhlaza.
Sekukonke, sibonise ukuthi i-Ni(OH)2-NS kanye ne-NiV-LDH-NS zivuselela i-COR ngendlela efanayo: i-cyclohexanone imuncwa ebusweni be-catalyst, ikhishwe i-hydrogen bese ilahlekelwa ama-electron ukuze yakhe i-1, esuke i-OH* i-oxidized ukuze yakhe i-2, ilandelwe ukuguqulwa kwezinyathelo eziningi ukuze kukhiqizwe i-AA (Isithombe 5c). Kodwa-ke, lapho i-cyclohexanone isetshenziswa njenge-reactant, ukuncintisana kwe-OER kwabonwa kuphela ku-Ni(OH)2-NS, kuyilapho inani eliphansi kakhulu le-oxygen laqoqwa lapho i-2 ne-3 zisetshenziswa njenge-reactants. Ngakho-ke, umehluko obonwe ekusebenzeni kwe-catalytic ungase ubangelwe izinguquko ku-RDS energy barrier kanye nekhono lokufaka i-cyclohexanone elibangelwa ukuguqulwa kwe-V esikhundleni sezinguquko endleleni yokusabela. Ngakho-ke sihlaziye i-RDS yezindlela zokusabela kuzo zombili i-catalyst. Imiphumela ye-X-ray acoustic spectroscopy eshiwo ngenhla ikhombisa ukuthi ukuguqulwa kwe-V kushintsha i-RDS ku-COR reaction kusuka esigabeni sokwakhiwa kabusha kuya esigabeni samakhemikhali, kugcina isigaba se-NiOOH kanye nezinhlobo ze-Ni ezi-valent eziphezulu zingasebenzi ku-NiV-LDH-NS (Isithombe 3f, Umfanekiso Ongeziwe 24, kanye neNothi 4). Sihlaziye kabanzi izinqubo zokusabela ezimelelwe yi-current density engxenyeni ngayinye yezifunda ezihlukene ezikhona ngesikhathi sokulinganisa i-CV (bheka Umfanekiso Ongeziwe 31 kanye neNothi 8 ukuthola imininingwane) futhi senze izivivinyo zokushintshana kwe-H/D kinetic isotope, ezibonise ndawonye ukuthi i-RDS ye-COR ku-NiV-LDH-NS ihilela ukuqhekeka kwesibopho se-Cα − H esigabeni samakhemikhali kunesigaba sokunciphisa (bheka Umfanekiso Ongeziwe 32 kanye neNothi 8 ukuthola imininingwane eyengeziwe).
Ngokusekelwe ekuhlaziyweni okungenhla, umphumela ophelele wokuguqulwa kwe-V uboniswe ku-Figure 5d. Ama-catalyst e-Ni(OH)2-NS kanye ne-NiV-LDH-NS akhiwa kabusha endaweni ephezulu kuma-anodic potentials futhi avuselela i-COR ngendlela efanayo. Ku-Ni(OH)2-NS (Isithombe 5d, kwesobunxele), isinyathelo sokwakhiwa kabusha yi-RDS ngesikhathi senqubo ye-COR; ngenkathi ku-NiV-LDH-NS (Isithombe 5d, kwesokudla), ukuguqulwa kwe-V kwasheshisa kakhulu inqubo yokwakha kabusha futhi kwaguqula i-RDS yaba yi-Cα−H dehydrogenation ye-cyclohexanone ukuze yakhe i-1. Ngaphezu kwalokho, ukumuncwa kwe-cyclohexanone kwenzeke endaweni ye-V futhi kwathuthukiswa ku-NiV-LDH-NS, okwaba negalelo ekucindezelweni kwe-OER.
Uma sibheka ukusebenza okuhle kakhulu kwe-electrocatalytic kwe-NiV-LDH-NS ene-FE ephezulu ngaphezu kobubanzi obukhona, saklama i-MEA ukuze sifeze ukukhiqizwa okuqhubekayo kwe-AA. I-MEA yahlanganiswa kusetshenziswa i-NiV-LDH-NS njenge-anode, i-PtRu/C yezohwebo njenge-cathode53 kanye ne-membrane yokushintshana kwe-anion (uhlobo: FAA-3-50) (Isithombe 6a kanye nesithombe esengeziwe 33)54. Njengoba i-voltage yeseli yehlile futhi i-FE ye-AA yayifana ne-0.5 M KOH esifundweni esingenhla, ukuhlushwa kwe-anolyte kwalungiswa kwaba yi-1 M KOH (Isithombe Esengeziwe 25c). Ama-curve e-LSV aqoshiwe aboniswe ku-Supplementary Fig. 34, okubonisa ukuthi ukusebenza kahle kwe-COR kwe-NiV-LDH-NS kuphakeme kakhulu kunokwe-Ni(OH)2-NS. Ukuze kuboniswe ukuphakama kwe-NiV-LDH-NS, kwenziwa i-electrolysis yamanje engaguquki nge-step current density esukela ku-50 kuya ku-500 mA cm−2 futhi i-voltage yeseli ehambisanayo yaqoshwa. Imiphumela ibonise ukuthi i-NiV-LDH-NS ibonise i-voltage yeseli engu-1.76 V ku-current density engu-300 mA cm−2, eyayiphansi cishe ngo-16% kune-Ni(OH)2-NS (2.09 V), okubonisa ukusebenza kwayo kahle kwamandla okuphezulu ekukhiqizweni kwe-AA (Isithombe 6b).
Umdwebo weskimu webhethri lokugeleza. b I-voltage yeseli ngaphandle kwesinxephezelo se-iR ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS ku-1 M KOH kanye ne-0.4 M cyclohexanone ekujuleni kwamanje okuhlukile. c I-AA kanye ne-FE ziyakhiqiza ku-Ni(OH)2-NS kanye ne-NiV-LDH-NS ekujuleni kwamanje okuhlukile. Amabha amaphutha amelela ukuphambuka okujwayelekile kwezilinganiso ezimbili ezizimele kusetshenziswa i-catalyst efanayo. d Ukuqhathaniswa kokusebenza kwe-catalytic komsebenzi wethu nezinye izinhlelo zebhethri lokugeleza ezibikiwe14,17,19. Amapharamitha okusabela kanye nezici zokusabela kubhalwe ngokuningiliziwe kuThebula Elingeziwe 2. e I-voltage yeseli kanye ne-FE ye-AA ku-NiV-LDH-NS ku-200 kanye no-300 mA cm−2 esivivinyweni sesikhathi eside, ngokulandelana. Idatha eluhlaza ye-be inikezwa njengefayela ledatha eluhlaza.
Okwamanje, njengoba kuboniswe ku-Fig. 6c, i-NiV-LDH-NS ngokuyisisekelo igcine i-FE enhle (83% kuya ku-61%) ku-current density ephezulu (200 kuya ku-500 mA cm-2), ngaleyo ndlela ithuthukisa umkhiqizo we-AA (1031 kuya ku-1900 μmol cm-2 h-1). Okwamanje, yi-0.8% kuphela yama-anion e-adipic acid abonwe endaweni ye-cathode ngemuva kwe-electrolysis, okubonisa ukuthi ukuguquka kwe-cyclohexanone kwakungabonakali esimweni sethu (Isithombe Esingeziwe 35). Ngokuphambene nalokho, ngesilinganiso esifanayo sokukhuphuka kobuningi bamanje, i-FE ye-AA ku-Ni(OH)2-NS yehle kusuka ku-61% kuya ku-34%, okwenza kwaba nzima ukuthuthukisa umkhiqizo we-AA (762 kuya ku-1050 μmol cm-2 h-1). Ikakhulukazi, ukusebenza kwe-AA kwehle kancane ngenxa yokuncintisana okunamandla okuvela ku-OER, ngakho-ke i-FE ye-AA yehle kakhulu ngokwanda kobuningi bamanje (kusuka ku-200 kuya ku-250 mA cm−2, Umfanekiso Ongeziwe 5). Ngokwazi kwethu, imiphumela ye-catalytic esebenzisa i-MEA ene-catalysts ye-NiV-LDH-NS idlula kakhulu ukusebenza kwe-flow reactors ebikwe ngaphambilini ene-catalysts esekelwe ku-Ni (Ithebula Elingeziwe 2). Ngaphezu kwalokho, njengoba kuboniswe ku-Fig. 6d, i-NiV-LDH-NS ibonise izinzuzo ezibalulekile maqondana nobuningi bamanje, i-voltage yeseli, kanye ne-FE ye-AA uma kuqhathaniswa ne-catalyst esebenza kahle kakhulu esekelwe ku-Co, okungukuthi, i-Co3O4 esekelwa yi-graphene (Co3O4/GDY)17. Ngaphezu kwalokho, sihlole ukusetshenziswa kwamandla kokukhiqiza kwe-AA futhi sabonisa ukuthi ukusetshenziswa kwe-AA kwakuphansi kakhulu, kungu-2.4 W h gAA-1 kuphela ku-current density engu-300 mA cm-2 kanye ne-voltage yeseli engu-1.76 V (izibalo ezinemininingwane zinikezwe ku-Supplementary Note 1). Uma kuqhathaniswa nomphumela omuhle kakhulu we-4.1 W h gAA-1 we-Co3O4/GDY ebikwe ngaphambilini, ukusetshenziswa kwamandla kokukhiqiza kwe-AA emsebenzini wethu kwehliswe ngo-42% futhi umkhiqizo wanda izikhathi ezine (1536 vs. 319 μmol cm-2 h-1)17.
Ukuqina kwe-catalyst ye-NiV-LDH-NS yokukhiqizwa kwe-AA yesikhathi eside ku-MEA kuhlolwe ngobuningi bamanje obungu-200 no-300 mA cm-2, ngokulandelana (Isithombe 6e). Njengoba i-OH− isetshenziswa ngokushesha ngobuningi bamanje obuphezulu, izinga lokuvuselelwa kwe-electrolyte ku-300 mA cm-2 liphakeme kunalelo eliku-200 mA cm-2 (bheka isigaba esithi “Izilinganiso ze-Electrochemical” ukuthola imininingwane). Ngobuningi bamanje obungu-200 mA cm-2, isilinganiso sokusebenza kahle kwe-COR sasingu-93% emahoreni ayi-6 okuqala, sabe sesehla kancane saya ku-81% ngemva kwamahora angama-60, kuyilapho i-voltage yeseli ikhuphuke kancane ngo-7% (kusuka ku-1.62 V kuya ku-1.73 V), okubonisa ukuqina okuhle. Njengoba ubuningi bamanje bukhula bufika ku-300 mA cm−2, ukusebenza kahle kwe-AA kwahlala kungashintshi (kwehle kusuka ku-85% kuya ku-72%), kodwa i-voltage yeseli yanda kakhulu (kusuka ku-1.71 kuya ku-2.09 V, okuhambisana no-22%) ngesikhathi sokuhlolwa kwamahora angu-46 (Isithombe 6e). Sicabanga ukuthi isizathu esiyinhloko sokuwohloka kokusebenza ukugqwala kwe-anion exchange membrane (AEM) yi-cyclohexanone, okuholela ekwandeni kokumelana kweseli kanye ne-voltage yeseli le-electrolyzer (Isithombe Esingeziwe 36), okuhambisana nokuvuza okuncane kwe-electrolyte kusuka ku-anode kuya ku-cathode, okuholela ekwehleni kwevolumu ye-anolyte kanye nesidingo sokumisa i-electrolysis. Ngaphezu kwalokho, ukwehla kwe-FE ye-AA nakho kungaba ngenxa yokugeleza kwama-catalyst, okukhuthaza ukuvulwa kwe-Ni foam ye-OER. Ukuze sibonise umthelela we-AEM ebolile ekuwohlokeni kokuzinza ku-300 mA cm−2, sayishintsha nge-AEM entsha ngemva kwamahora angu-46 e-electrolysis. Njengoba bekulindelekile, ukusebenza kahle kwe-catalytic kwabuyiselwa ngokusobala, lapho i-voltage yeseli yehla kakhulu yaba yinani lokuqala (kusukela ku-2.09 kuya ku-1.71 V) bese ikhula kancane phakathi kwamahora angu-12 alandelayo e-electrolysis (kusukela ku-1.71 kuya ku-1.79 V, ukwanda okungu-5%; Isibalo 6e).
Sekukonke, sikwazile ukufeza ukuzinza kokukhiqizwa kwe-AA okuqhubekayo kwamahora angama-60 ku-current density engu-200 mA cm−2, okubonisa ukuthi i-FE kanye ne-cell voltage ye-AA zigcinwa kahle. Sizame futhi u-current density ophezulu wamahora angama-300 mA cm−2 futhi sathola ukuzinza okuphelele kwamahora angama-58, sathatha indawo ye-AEM entsha ngemva kwamahora angama-46. Izifundo ezingenhla zibonisa ukuzinza kwe-catalyst futhi zibonisa ngokusobala isidingo sokuthuthukiswa kwesikhathi esizayo kwama-AEM anamandla aphezulu ukuthuthukisa ukuzinza kwesikhathi eside kwe-MEA kokukhiqizwa kwe-AA okuqhubekayo ku-current densities efanele imboni.
Ngokusekelwe ekusebenzeni kwe-MEA yethu, siphakamise inqubo ephelele yokukhiqiza i-AA ehlanganisa ukondla i-substrate, i-electrolysis, i-neutralization, kanye namayunithi okuhlukanisa (Isithombe Esingeziwe 37). Ukuhlaziywa kokusebenza kokuqala kwenziwe ukuhlola ukusebenza kahle komnotho kohlelo kusetshenziswa imodeli yokukhiqiza i-alkaline electrolyte electrocatalytic carboxylate55. Kulesi simo, izindleko zifaka phakathi imali, imisebenzi, kanye nezinto zokwakha (Isithombe 7a kanye nesithombe Esingeziwe 38), kanye nemali engenayo ivela ekukhiqizweni kwe-AA kanye ne-H2. Imiphumela ye-TEA ikhombisa ukuthi ngaphansi kwezimo zethu zokusebenza (ubuningi bamanje obungu-300 mA cm-2, i-voltage yeseli engu-1.76 V, FE 82%), izindleko kanye nemali engenayo iyonke ingu-US$2429 kanye no-US$2564, ngokulandelana, okuhunyushwa kube yinzuzo eningi engu-US$135 ngethani le-AA elikhiqizwe (bheka Inothi Elingeziwe 9 ukuthola imininingwane).
a Izindleko eziphelele zenqubo ye-electrochemical ye-AA ngaphansi kwesimo sesisekelo secala nge-FE engu-82%, ubuningi bamanje obungu-300 mA cm−2, kanye ne-voltage yeseli engu-1.76 V. Ukuhlaziywa kokuzwela kwezindleko ezintathu ku-b FE kanye nobuningi bamanje buka-c. Ekuhlaziyweni kokuzwela, amapharamitha afundwe kuphela ahlukanisiwe kanti amanye amapharamitha agcinwa engaguquki ngokusekelwe kumodeli ye-TEA. d Imiphumela ye-FE ehlukene kanye nobuningi bamanje enzuzweni ye-electrosynthesis ye-AA kanye nenzuzo kusetshenziswa i-Ni(OH)2-NS kanye ne-NiV-LDH-NS, kucatshangwa ukuthi i-voltage yeseli igcinwa ingaguquki ku-1.76 V. Idatha yokufaka ye-a–d inikezwa kufayela ledatha eluhlaza.
Ngokusekelwe kulesi sisekelo, siqhubekile nokuhlola umthelela we-FE kanye nobuningi bamanje enzuzweni yokwenziwa kwe-electrosynthesis ye-AA. Sithole ukuthi inzuzo ibucayi kakhulu ku-FE ye-AA, njengoba ukwehla kwe-FE kuholela ekwandeni okukhulu kwezindleko zokusebenza, ngaleyo ndlela kwandise kakhulu izindleko zizonke (Isithombe 7b). Ngokuphathelene nobuningi bamanje, ubuningi bamanje obuphezulu (>200 mA cm-2) kusiza ukunciphisa izindleko zenhloko-dolobha kanye nezindleko zokwakha izitshalo, ikakhulukazi ngokunciphisa indawo yeseli ye-electrolytic, ngaleyo ndlela kunegalelo ekwandeni kwenzuzo (Isithombe 7c). Uma kuqhathaniswa nobuningi bamanje, i-FE inomthelela obaluleke kakhulu enzuzweni. Ngokuchaza umthelela we-FE kanye nobuningi bamanje enzuzweni, sibona ngokucacile ukubaluleka kokufinyelela i-FE ephezulu (>60%) ekuminyaneni kwamanje okuhlobene nezimboni (>200 mA cm-2) ukuqinisekisa inzuzo. Ngenxa yenani eliphezulu le-FE le-AA, uhlelo lokusabela olune-NiV-LDH-NS njenge-catalyst luhlala luhle ebangeni eliphakathi kuka-100–500 mA cm−2 (amachashazi e-pentagram; Umfanekiso 7d). Kodwa-ke, ku-Ni(OH)2-NS, ukwehlisa i-FE ekuxineni kwamanje okuphezulu (>200 mA cm−2) kwaholela emiphumeleni engemihle (imibuthano; Umfanekiso 7d), okugqamisa ukubaluleka kwama-catalyst ane-FE ephezulu ekuxineni kwamanje okuphezulu.
Ngaphezu kokubaluleka kwama-catalyst ekunciphiseni izindleko zemali kanye nokusebenza, ukuhlolwa kwethu kwe-TEA kusikisela ukuthi inzuzo ingathuthukiswa ngezindlela ezimbili. Eyokuqala ukuthengisa i-potassium sulfate (K2SO4) emakethe njengomkhiqizo ongaphansi kweyunithi yokungahlanganisi, kodwa ngenzuzo engaba khona engu-US$828/t AA-1 (Inothi Elingeziwe 9). Esesibili ukwenza ngcono ubuchwepheshe bokucubungula, okuhlanganisa ukuphinda kusetshenziswe izinto noma ukuthuthukiswa kobuchwepheshe bokuhlukanisa i-AA obungabizi kakhulu (ezinye izindlela zokunciphisa nokuhlukanisa amayunithi). Inqubo yokungahlanganisi i-acid-base esetshenziswa njengamanje ingabangela izindleko eziphezulu zezinto (ezibala isabelo esikhulu ku-85.3%), lapho u-94% wazo ubangelwa yi-cyclohexanone kanye ne-KOH ($2069/t AA-1; Umfanekiso 7a), kodwa njengoba kushiwo ngenhla, inqubo isenenzuzo iyonke. Siphakamisa ukuthi izindleko zezinto zingancishiswa kakhulu ngezindlela ezithuthukisiwe zokubuyisa i-KOH kanye ne-cyclohexanone engaphenduliwe, njenge-electrodialysis yokubuyisa ngokuphelele i-KOH14 (izindleko ezilinganisiwe ze-US$1073/t AA-1 nge-electrodialysis; Inothi Elingeziwe 9).
Ngamafuphi, sifinyelele ukusebenza kahle okuphezulu kwe-electrolysis ye-athomu ye-aluminium ku-high current density ngokwethula i-V kuma-nanosheet e-Ni(OH)2. Ngaphansi kobubanzi obungaba khona be-1.5–1.9 VRHE kanye ne-high current density engu-170 mA cm−2, i-AA FE ku-NiV-LDH-NS ifinyelele ku-83–88%, kuyilapho i-OER icindezelwe ngempumelelo ku-3%. Ukuguqulwa kwe-V kukhuthaze ukwehla kwe-Ni2+ ku-Ni3+x futhi kwathuthukisa ukumuncwa kwe-cyclohexanone. Idatha yokuhlola neyethiyori ikhombisa ukuthi ukwakhiwa kabusha okuvuselelwe kwandisa ubuningi bamanje be-cyclohexanone oxidation futhi kushintsha i-RDS ye-COR kusukela ekwakhiweni kabusha kuya ekuncipheni kwe-hydrogenation okubandakanya i-Cα − H scission, kuyilapho ukumuncwa okuthuthukisiwe kwe-cyclohexanone kucindezela i-OER. Ukuthuthukiswa kwe-MEA kufinyelele ekukhiqizweni kwe-AA okuqhubekayo ku-density yamanje yezimboni engu-300 mA cm−2, ukusebenza kahle kwe-AA okurekhodiwe okungu-82%, kanye nokukhiqiza okungu-1536 μmol cm−2 h−1. Ukuhlolwa kwamahora angu-50 kubonise ukuthi i-NiV-LDH-NS inokuqina okuhle njengoba ingagcina i-AA FE ephezulu ku-MEA (> 80% amahora angu-60 ku-200 mA cm−2; > 70% amahora angu-58 ku-300 mA cm−2). Kufanele kuqashelwe ukuthi kunesidingo sokuthuthukisa ama-AEM anamandla kakhulu ukuze kufezwe ukuzinza kwesikhathi eside ku-density yamanje efaneleke kakhulu kwezimboni. Ngaphezu kwalokho, i-TEA igcizelela izinzuzo zezomnotho zamasu okusabela ekukhiqizweni kwe-AA kanye nokubaluleka kwama-catalyst asebenza kahle kanye nobuchwepheshe bokuhlukanisa obuthuthukisiwe ukuze kuncishiswe izindleko.