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Ukwenziwa kwe-electrosynthesis ye-adipic acid (i-precursor ye-nylon 66) evela kwi-oyile ye-CA (umxube we-cyclohexanone kunye ne-cyclohexanol) sisicwangciso esizinzileyo esinokuthatha indawo yeendlela zemveli ezifuna iimeko ezinzima. Nangona kunjalo, uxinano oluphantsi lwamandla kunye neempendulo zokuvela kwe-oxygen ezikhuphisanayo zithintela kakhulu ukusetyenziswa kwayo kwimizi-mveliso. Kulo msebenzi, sitshintsha i-nickel double hydroxide kunye ne-vanadium ukuphucula uxinano lwamandla kunye nokugcina ukusebenza kakuhle kwe-faradaic (>80%) kuluhlu olubanzi lwamandla (1.5–1.9 V vs. i-hydrogen electrode eguqukayo). Izifundo zovavanyo kunye nethiyori zityhile iindima ezimbini ezibalulekileyo zokuguqulwa kwe-V, kubandakanya ukwakhiwa kwakhona kwe-catalyst okukhawulezileyo kunye nokuphuculwa kwe-cyclohexanone adsorption. Njengobungqina bengcamango, sakhe i-membrane-electrode assembly evelise i-adipic acid enobuchule obuphezulu be-faradaic (82%) kunye nemveliso (1536 μmol cm-2 h-1) kuxinano lwamandla oluhambelana nemizi-mveliso (300 mA cm-2), ngelixa sifezekisa uzinzo >50 h. Lo msebenzi ubonisa isikhuthazo esisebenzayo sokwenza i-electrosynthesis ye-adipic acid enemveliso ephezulu kunye namandla emizi-mveliso.
I-Adipic acid (AA) yenye yezona asidi zibalulekileyo ze-aliphatic dicarboxylic kwaye isetyenziswa kakhulu ekuveliseni i-nylon 66 kunye nezinye ii-polyamides okanye ii-polymers1. Kwimizi-mveliso, i-AA yenziwa ngokuxovula umxube we-cyclohexanol kunye ne-cyclohexanone (oko kukuthi, ioyile ye-AA) kusetyenziswa i-50–60 vol% nitric acid njenge-oxidizing agent. Le nkqubo ineengxaki zokusingqongileyo ezinxulumene nokukhutshwa kwe-nitric acid egxininisiweyo kunye ne-nitrogen oxides (N2O kunye ne-NOx) njengeegesi ze-greenhouse2,3. Nangona i-H2O2 ingasetyenziswa njenge-arhente eluhlaza exovula ulwelo, iindleko zayo eziphezulu kunye neemeko ezinzima zokwenza izinto zenza kube nzima ukuyisebenzisa ngokoqobo, kwaye kufuneka indlela engabizi kakhulu nehlala ixesha elide4,5,6.
Kwiminyaka elishumi edlulileyo, iindlela zokwenziwa kweekhemikhali kunye namafutha nge-electrocatalytic ziye zatsala ingqalelo eyandayo kwiingcali zesayensi ngenxa yeengenelo zazo zokusebenzisa amandla avuselelekayo kunye nokusebenza phantsi kweemeko ezibuthathaka (umz., ubushushu begumbi kunye noxinzelelo lwe-ambient)7,8,9,10. Kule meko, uphuhliso lokuguqulwa kwe-electrocatalytic yeoyile ye-KA ibe yi-AA kubaluleke kakhulu ukufumana iingenelo ezingentla kunye nokuphelisa ukusetyenziswa kwe-nitric acid kunye ne-nitrous oxide emissions edibana nayo kwimveliso eqhelekileyo (Umfanekiso 1a). Umsebenzi wokuqala wenziwe nguPetrosyan et al., ababike ukuba i-electrocatalytic oxidation reaction ye-cyclohexanone (COR; cyclohexanone okanye i-cyclohexanol ziye zafundwa ngokubanzi njengezimele ioyile ye-KA) kwi-nickel oxyhydroxide (NiOOH), kodwa uxinano lwangoku oluphantsi (6 mA cm-2) kunye ne-AA yield ephakathi (52%) zifunyenwe11,12. Ukususela ngoko, kuye kwenziwa inkqubela phambili ebalulekileyo kuphuhliso lwee-catalysts ezisekelwe kwi-nickel ukuphucula umsebenzi we-COR. Umzekelo, i-catalyst ye-nickel hydroxide (Cu-Ni(OH)2) eyenziwe nge-copper-doped yenziwe ukuze ikhuthaze ukuqhekeka kwe-Cα-Cβ kwi-cyclohexanol13. Kutshanje sixele nge-catalyst ye-Ni(OH)2 eguqulwe nge-sodium dodecyl sulfonate (SDS) ukuze yenze i-microenvironment engaphobiyo etyebisa i-cyclohexanone14.
a Imingeni yokuveliswa kwe-AA nge-electrooxidation yeoyile ye-KA. b Ukuthelekiswa kwe-COR ye-electrocatalytic yee-catalysts ezisekelwe kwi-Ni ezixeliweyo ngaphambili kunye ne-catalyst yethu kwinkqubo ye-electrode ezintathu kunye nenkqubo yebhetri yokuhamba11,13,14,16,26. Ulwazi oluneenkcukacha malunga neeparameter zempendulo kunye nokusebenza kwempendulo lubonelelwe kwiiTheyibhile ezongezelelweyo 1 kunye no-2. c Ukusebenza kwe-Catalytic kwee-catalysts zethu ze-NiV-LDH-NS ze-COR kwi-reactor ye-H-cell kunye ne-MEA, ezisebenza kuluhlu olubanzi lwamandla.
Nangona ezi ndlela zingasentla ziphucule umsebenzi we-COR, ii-catalysts ezisekelwe kwi-Ni ezichazwe apha zibonise ukusebenza okuphezulu kwe-AA Faraday (FE) (>80%) kuphela kwii-potentials eziphantsi kakhulu, ngokuqhelekileyo zingaphantsi kwe-1.6 V xa kuthelekiswa ne-hydrogen electrode eguquguqukayo (RHE, efinyeziweyo nge-VRHE). Ngoko ke, i-partial current density exeliweyo (oko kukuthi, i-total current density ephindaphindwe yi-FE) ye-AA isoloko ingaphantsi kwe-60 mA cm−2 (Umfanekiso 1b kunye neTheyibhile eyoNgezelelweyo 1). I-low current density ingaphantsi kakhulu kweemfuno zoshishino (>200 mA cm−2)15, nto leyo ethintela kakhulu iteknoloji ye-electrocatalytic yokwenza i-AA ephezulu (Umfanekiso 1a; phezulu). Ukwandisa i-current density, i-positive potential (yenkqubo ye-three-electrode) okanye i-voltage ephezulu yeseli (yenkqubo ye-two-electrode) ingasetyenziswa, eyindlela elula yokuguqulwa kwe-electrocatalytic okuninzi, ingakumbi i-oxygen evolution reaction (OER). Nangona kunjalo, kwi-COR kwi-anodic potentials ephezulu, i-OER inokuba ngumncintisani omkhulu ekunciphiseni i-FE ye-AA, ngaloo ndlela inciphisa ukusebenza kakuhle kwamandla (Umfanekiso 1a; ezantsi). Umzekelo, xa sijonga inkqubela yangaphambili (Umfanekiso 1b kunye neTheyibhile eyoNgezelelweyo 1), siphoxekile kukufumanisa ukuba i-FE ye-AA kwi-SDS-modified Ni(OH)2 yehle ukusuka kwi-93% ukuya kwi-76% ngokunyusa amandla asetyenzisiweyo ukusuka kwi-1.5 VRHE ukuya kwi-1.7 VRHE14, ngelixa i-FE ye-AA kwi-CuxNi1-x(OH)2/CF yehle ukusuka kwi-93% ukuya kwi-69% ngokunyusa amandla ukusuka kwi-1.52 VRHE ukuya kwi-1.62 VRHE16. Ke ngoko, uxinano lwangoku oluyinxenye oluxeliweyo lwe-AA alunyuki ngokulinganayo kwi-potentials ephezulu, nto leyo ethintela kakhulu ukuphuculwa kokusebenza kwe-AA, ingasathethwa ke ngokusetyenziswa kwamandla aphezulu ngenxa ye-FE ephantsi ye-AA. Ukongeza kwiikhatalysts ezisekelwe kwi-nickel, iikhatalysts ezisekelwe kwi-cobalt nazo zibonakalise umsebenzi we-catalytic kwi-COR17,18,19. Nangona kunjalo, ukusebenza kwazo kuncipha kwiikhontenti eziphezulu, kwaye xa kuthelekiswa neekhatalysts ezisekelwe kwi-Ni, zinemida engakumbi kwizicelo zoshishino, ezifana nokuguquguquka kwamaxabiso amakhulu kunye neempahla ezincinci. Ke ngoko, kuyacetyiswa ukuphuhlisa iikhatalysts ezisekelwe kwi-Ni ezine-current density ephezulu kunye ne-FE kwi-COR ukuze kube lula ukufikelela kwisivuno esiphezulu se-AA.
Kulo msebenzi, sixela ii-nanosheets ze-nickel eziguqulweyo ze-nickel (NiV-LDH-NS) ze-vanadium(V)-modified nickel layered double hydroxide nanosheets (NiV-LDH-NS) njengee-electrocatalysts ezisebenzayo zokuvelisa i-AA nge-COR, ezisebenza kuluhlu olubanzi lwe-potential nge-OER ecinezelweyo kakhulu, zifikelela kwi-FE ephezulu kunye ne-current density kuzo zombini ii-H-cells kunye ne-membrane electrode assemblies (MEAs; Umfanekiso 1 b). Okokuqala sibonisa ukuba ukusebenza kakuhle kwe-acetylene oxidation phezu kwe-Ni(OH)2 nanosheet catalyst eqhelekileyo (Ni(OH)2-NS) kwehla, njengoko kulindelekile, kwi-potentials ephezulu, ukusuka kwi-80% kwi-1.5 VRHE ukuya kwi-42% kwi-1.9 VRHE. Ngokwahlukileyo kakhulu, emva kokuguqula i-Ni(OH)2 nge-V, i-NiV-LDH-NS ibonise i-current density ephezulu kwi-potential ethile kwaye, okubaluleke ngakumbi, igcine i-FE ephezulu kuluhlu olubanzi lwe-potential. Umzekelo, kwi-1.9 VRHE, ibonise uxinano lwangoku lwe-170 mA cm−2 kunye ne-FE ye-83%, eyi-catalyst elungele ngakumbi i-COR kwinkqubo ye-electrode ezintathu (Umzobo 1c kunye neTheyibhile eyoNgezelelweyo 1). Idatha yovavanyo kunye neyethiyori ibonisa ukuba ukuguqulwa kwe-V kukhuthaza i-reduction kinetics ukusuka kwi-Ni(OH)2 ukuya kwi-high-valent Ni oxyhydroxides (Ni3+xOOH1-x), ezisebenza njengesigaba esisebenzayo se-COR. Ngaphezu koko, ukuguqulwa kwe-V kuphucula ukutsalwa kwe-cyclohexanone kumphezulu we-catalyst, edlale indima ephambili ekucinezeleni i-OER kwi-anodic potentials ephezulu. Ukubonisa amandla e-NiV-LDH-NS kwimeko enokwenzeka ngakumbi, siyile i-MEA flow reactor kwaye sabonisa i-FE ye-AA (82%) kwi-current density efanelekileyo kwimizi-mveliso (300 mA cm−2), ephezulu kakhulu kuneziphumo zethu zangaphambili kwi-membrane flow reactor (Umzobo 1b kunye neTheyibhile eyoNgezelelweyo 2). Isivuno esihambelanayo se-AA (1536 μmol cm−2 h−1) sasiphezulu nangakumbi kuneso sifunyenwe kusetyenziswa inkqubo ye-thermal catalytic (<30 mmol gcatalyst−1 h−1)4. Ngaphezu koko, i-catalyst ibonise uzinzo oluhle xa kusetyenziswa i-MEA, igcina i-FE >80% AA kangangeeyure ezingama-60 kwi-200 mA cm−2 kunye ne-FE >70% AA kangangeeyure ezingama-58 kwi-300 mA cm−2. Okokugqibela, uphando lokuqala lokwenzeka (i-FEA) lubonise ukusebenza kakuhle kwesicwangciso se-electrocatalytic kwimveliso ye-AA.
Ngokweencwadi zangaphambili, i-Ni(OH)2 yi-catalyst eqhelekileyo ebonisa umsebenzi olungileyo we-COR, ngoko ke i-Ni(OH)2-NS13,14 yenziwe okokuqala ngendlela ye-coprecipitation. Iisampuli zibonise isakhiwo se-β-Ni(OH)2, esaqinisekiswa yi-X-ray diffraction (XRD; Fig. 2a), kwaye ii-nanosheets ezibhityileyo kakhulu (ubukhulu: 2–3 nm, ubungakanani obusecaleni: 20–50 nm) zabonwa nge-high-resolution transmission electron microscopy (HRTEM; Supplementary Fig. 1) kunye ne-atomic force microscopy (AFM) measurements (Supplementary Fig. 2). Ukuhlanganiswa kwee-nanosheets kwabonwa ngenxa yendalo yazo ebhityileyo kakhulu.
iipateni ze-X-ray diffraction ze-Ni(OH)2-NS kunye ne-NiV-LDH-NS. I-FE, i-throughput, kunye ne-AA current density kwi-b Ni(OH)2-NS kunye ne-c NiV-LDH-NS kwii-potentials ezahlukeneyo. Ii-error bars zimele ukuphambuka okuqhelekileyo kwemilinganiselo emithathu ezimeleyo kusetyenziswa i-catalyst efanayo. d Umfanekiso we-HRTEM we-NV-LDH-NS. I-scale bar: 20 nm. Umfanekiso we-HAADF-STEM we-NiV-LDH-NS kunye nemephu ye-elemental ehambelanayo ebonisa ukusasazwa kwe-Ni (eluhlaza), i-V (etyheli), kunye ne-O (eluhlaza okwesibhakabhaka). I-scale bar: 100 nm. f Ni 2p3/2, g O 1 s, kunye ne-h V 2p3/2 XPS data ye-Ni(OH)2-NS (phezulu) kunye ne-NiV-LDH-NS (ezantsi). i-FE kunye ne-j zi-AA performances kwi-catalysts ezimbini kwimijikelo esi-7. Ii-error bars zimele ukuphambuka okuqhelekileyo kwemilinganiselo emithathu ezimeleyo kusetyenziswa i-catalyst efanayo kwaye zingaphakathi kwe-10%. Idatha eluhlaza ye-a–c kunye ne-f–j inikezelwa kwiifayile zedatha eluhlaza.
Emva koko sivavanye isiphumo seNi(OH)2-NS kwiCOR. Sisebenzisa i-electrolysis engapheliyo, sifumene i-80% ye-FE ye-AA kwi-low potential (1.5 VRHE) ngaphandle kwe-OER (Umfanekiso 2b), nto leyo ebonisa ukuba i-COR ilunge ngakumbi ngamandla kune-OER kwi-low anodic potentials. Imveliso ephambili ephumayo ifunyenwe ukuba yi-glutaric acid (GA) ene-FE ye-3%. Ubukho be-trace amounts ye-succinic acid (SA), i-malonic acid (MA), kunye ne-oxalic acid (OA) nayo yalinganiswa yi-HPLC (jonga uMfanekiso oNcedisayo 3 wokusasazwa kwemveliso). Akukho formic acid efunyenweyo kwimveliso, nto leyo ebonisa ukuba i-carbonate inokwenziwa njenge-C1 by-product. Ukuvavanya le ngcamango, i-electrolyte evela kwi-electrolysis epheleleyo ye-0.4 M cyclohexanone yafakwa i-acid kwaye iimveliso zegesi zadlula kwisisombululo se-Ca(OH)2. Ngenxa yoko, isisombululo saba yi-turbid, siqinisekisa ukwakheka kwe-carbonate emva kwe-electrolysis. Nangona kunjalo, ngenxa yombane ophantsi oveliswayo ngexesha lenkqubo ye-electrolysis (Umfanekiso 2b, c), uxinzelelo lwe-carbonate luphantsi kwaye kunzima ukululinganisa. Ukongeza, ezinye iimveliso ze-C2-C5 nazo zinokwenziwa, kodwa ubungakanani bazo abunakulinganiswa. Nangona isixa siphela seemveliso kunzima ukusilinganisa, i-90% yesixa siphela se-electrochemical equivalent ibonisa ukuba uninzi lweenkqubo ze-electrochemical zichongiwe, nto leyo enika isiseko sokuqonda kwethu oomatshini. Ngenxa yoxinano oluphantsi lwangoku (20 mA cm−2), isivuno se-AA sasiyi-97 μmol cm−2 h−1 (Umfanekiso 2b), esilingana ne-19 mmol h−1 g−1 ngokusekelwe kumthwalo wobunzima be-catalyst (5 mg cm−2), engaphantsi kunemveliso ye-thermal catalytic (~30 mmol h−1 g−1)1. Xa amandla asetyenziswayo anda ukusuka kwi-1.5 ukuya kwi-1.9 VRHE, nangona uxinano lwangoku lulonke lunyukile (ukusuka kwi-20 ukuya kwi-114 mA cm−2), kwabakho ukwehla okukhulu kwi-AA FE ngaxeshanye, ukusuka kwi-80% ukuya kwi-42%. Ukwehla kwi-FE kwii-potentials ezintle ngakumbi kungenxa yokhuphiswano lwe-OER. Ingakumbi kwi-1.7 VRHE, ukhuphiswano lwe-OER lukhokelela ekunciphiseni okukhulu kwi-AA FE, ngaloo ndlela kunciphisa kancinci ukusebenza kwe-AA ngokwanda koxinano lwangoku lulonke. Ngoko ke, nangona uxinano lwangoku oluyinxenye lwe-AA lunyuke ukusuka kwi-16 ukuya kwi-48 mA cm−2 kwaye imveliso ye-AA inyukile (ukusuka kwi-97 ukuya kwi-298 μmol cm−2 h−1), kwasetyenziswa amandla amaninzi ongezelelweyo (2.5 W h gAA−1 ngaphezulu ukusuka kwi-1.5 ukuya kwi-1.9 VRHE), okubangele ukwanda kokukhutshwa kwekhabhoni kwe-2.7 g CO2 gAA−1 (iinkcukacha zokubala zinikwe kwiNqaku elongezelelweyo 1). I-OER ekhankanyiweyo ngaphambili njengomncintisani nempendulo ye-COR kwi-anodic potentials ephezulu iyahambelana neengxelo zangaphambili kwaye imele umngeni ngokubanzi wokuphucula imveliso ye-AA14,17.
Ukuze siphuhlise i-catalyst ye-COR esebenza kakuhle kakhulu esekelwe kwi-Ni(OH)2-NS, siqale sahlalutya isigaba esisebenzayo. Sibone iincopho kwi-473 cm-1 kunye ne-553 cm-1 kwiziphumo zethu ze-in situ Raman spectroscopy (Umzobo oNcedisayo 4), ohambelana nokugoba kunye nokwelulwa kweebhondi ze-Ni3+-O kwi-NiOOH, ngokulandelelana. Kuye kwabhalwa ukuba i-NiOOH sisiphumo sokunciphisa i-Ni(OH)2 kunye nokuqokelelwa kwe-Ni(OH)O kwii-anodic potentials, kwaye ngokuyintloko sisigaba esisebenzayo kwi-electrocatalytic oxidation20,21. Ke ngoko, silindele ukuba ukukhawulezisa inkqubo yokwakha kwakhona isigaba se-Ni(OH)2 ukuya kwi-NiOOH kunokuphucula umsebenzi we-catalytic we-COR.
Sizamile ukuguqula i-Ni(OH)2 ngeentsimbi ezahlukeneyo kuba kwabonwa ukuba ukuguqulwa kwe-heteroatom kukhuthaza ukwakhiwa kwakhona kwesigaba kwii-oxides zesinyithi eziguqukayo/ii-hydroxides22,23,24. Iisampuli zenziwe ngokudityaniswa kwe-Ni kunye ne-precursor yesibini yesinyithi. Phakathi kweesampuli ezahlukeneyo eziguqulwe ngesinyithi, isampuli eguqulwe nge-V (V:Ni atomic ratio 1:8) (ebizwa ngokuba yi-NiV-LDH-NS) ibonise uxinano oluphezulu lwamandla kwi-COR (Umzobo oNcedisayo 5) kwaye okubaluleke ngakumbi, i-AA FE ephezulu kwifestile ebanzi enokubakho. Ngokukodwa, kwi-potential ephantsi (1.5 VRHE), uxinano lwamandla angoku lwe-NiV-LDH-NS lwaluphezulu ngokuphindwe kayi-1.9 kune-Ni(OH)2-NS (39 vs. 20 mA cm−2), kwaye i-AA FE yayifana kuzo zombini ii-catalysts (83% vs. 80%). Ngenxa yoxinano oluphezulu lwangoku kunye ne-FE AA efanayo, imveliso ye-NiV-LDH-NS iphezulu ngokuphindwe ka-2.1 kuneye-Ni(OH)2-NS (204 vs. 97 μmol cm−2 h−1), ebonisa isiphumo sokukhuthaza ukuguqulwa kwe-V kwixinano lwangoku kwi-potentials eziphantsi (Umfanekiso 2c).
Ngokukhula kwamandla asetyenziswayo (umz., i-1.9 VRHE), uxinano lwangoku kwi-NiV-LDH-NS luphezulu ngokuphindwe kayi-1.5 kunolo lukwi-Ni(OH)2-NS (170 vs. 114 mA cm−2), kwaye ukwanda kufana noko kukwi-potentials eziphantsi (ngokuphindwe kayi-1.9). Okuphawulekayo kukuba, i-NiV-LDH-NS igcine i-AA FE ephezulu (83%) kwaye i-OER yancitshiswa kakhulu (O2 FE 4%; Umfanekiso 2c), iphumelela ngaphezu kwe-Ni(OH)2-NS kunye nee-catalysts ezixeliweyo ngaphambili ezine-AA FE esezantsi kakhulu kwi-anodic potentials eziphezulu (Itheyibhile eyongezelelweyo 1). Ngenxa ye-FE ephezulu ye-AA kwifestile ebanzi enokubakho (1.5–1.9 VRHE), izinga lokuveliswa kwe-AA le-867 μmol cm−2 h−1 (elilingana ne-174.3 mmol g−1 h−1) lifikelelwe kwi-1.9 VRHE, nto leyo ebonisa ukusebenza kakuhle kwiinkqubo ze-electrocatalytic kunye ne-thermocatalytic xa umsebenzi wawuqhelekile ngokulayishwa kobunzima obupheleleyo beesampuli ze-NiV-LDH-NS (Umzobo oNcedisayo 6).
Ukuze siqonde uxinano oluphezulu lwangoku kunye ne-FE ephezulu kuluhlu olubanzi lwamandla emva kokuguqula i-Ni(OH)2 kunye ne-V, sichaze ulwakhiwo lwe-NiV-LDH-NS. Iziphumo ze-XRD zibonise ukuba utshintsho olune-V lubangele utshintsho lwesigaba ukusuka kwi-β-Ni(OH)2 ukuya kwi-α-Ni(OH)2, kwaye akukho ntlobo zekristale ezinxulumene ne-V ezifunyenweyo (Umzobo 2a). Iziphumo ze-HRTEM zibonisa ukuba i-NiV-LDH-NS ifumana ilifa lemo ye-nanosheets ze-Ni(OH)2-NS ezincinci kakhulu kwaye zinemilinganiselo efanayo ecaleni (Umzobo 2d). Ukulinganiswa kwe-AFM kutyhile ukuthambekela okunamandla kokuhlanganiswa kwee-nanosheets, okubangele ubukhulu obulinganiswayo obumalunga ne-7 nm (Umzobo ongezelelweyo 7), obukhulu kunobo be-Ni(OH)2-NS (ubukhulu: 2–3 nm). Uhlalutyo lwemephu ye-spectroscopy ye-X-ray esasazeka ngamandla (Umfanekiso 2e) lubonise ukuba izinto ze-V kunye ne-Ni zisasazwe kakuhle kwii-nanosheets. Ukuze sicacise isakhiwo se-elektroniki se-V kunye nefuthe laso kwi-Ni, sisebenzise i-X-ray photoelectron spectroscopy (XPS) (Umfanekiso 2f–h). I-Ni(OH)2-NS ibonise iincopho ze-spin-orbit ze-Ni2+ (incopho yabasetyhini kwi-855.6 eV, incopho yesathelayithi kwi-861.1 eV, Umfanekiso 2f)25. I-O1 s XPS spectrum ye-Ni(OH)2-NS inokwahlulwa ibe ziincopho ezintathu, phakathi kwazo iincopho kwi-529.9, 530.9 kunye ne-532.8 eV zibangelwa yi-lattice oxygen (OL), iqela le-hydroxyl (Ni-OH) kunye ne-oxygen efakwe kwi-surface defects (OAds), ngokwahlukeneyo (Umfanekiso 2g)26,27,28,29. Emva kokuguqulwa nge-V, kwavela incochoyi ye-V 2p3/2, enokwahlulwa ibe ziincochoyi ezintathu ezikwi-517.1 eV (V5+), 516.6 eV (V4+) kunye ne-515.8 eV (V3+), ngokulandelelana, nto leyo ebonisa ukuba iintlobo ze-V kwisakhiwo zikho ikakhulu kwiimeko ze-oxidation ephezulu (Umfanekiso 2h)25,30,31. Ukongeza, incochoyi ye-Ni 2p kwi-855.4 eV kwi-NiV-LDH-NS yatshintshwa kakubi (malunga ne-0.2 eV) xa kuthelekiswa naleyo ikwi-Ni(OH)2-NS, nto leyo ebonisa ukuba ii-electron zidluliselwe kwi-V ukuya kwi-Ni. Imeko ye-valence ephantsi kakhulu ye-Ni ebonwe emva kokuguqulwa kwe-V yayihambelana neziphumo ze-Ni K-edge X-ray absorption near-edge spectroscopy (XANES) (jonga icandelo elithi "V Modification Promotes Catalyst Reduction" ngezantsi ukuze ufumane iinkcukacha ezithe vetshe). I-NiV-LDH-NS emva konyango lwe-COR kangangeyure eli-1 yabizwa ngokuba yi-NiV-LDH-POST kwaye yachazwa ngokupheleleyo kusetyenziswa i-transmission electron microscopy, i-EDS mapping, i-X-ray diffraction, i-Raman spectroscopy, kunye nokulinganisa i-XPS (Iimifanekiso ezongezelelweyo 8 kunye ne-9). Ii-catalysts zahlala njengee-aggregates ezine-ultrathin nanosheet morphology (Umzobo ongezelelweyo 8a–c). Ubukhali beesampuli behlile kwaye umxholo we-V wehla ngenxa ye-V leaching kunye ne-catalyst reconstruction (Umzobo ongezelelweyo 8d–f). Ii-XPS spectra zibonise ukwehla kwi-V peak intensity (Umzobo ongezelelweyo 9), okwabangelwa yi-V leaching. Ukongeza, uhlalutyo lwe-spectrum ye-O1s (Umzobo oNcedisayo 9d) kunye nokulinganiswa kwe-electron paramagnetic resonance (EPR) (Umzobo oNcedisayo 10) kubonise ukuba ubungakanani bezithuba ze-oxygen kwi-NiV-LDH-NS zanda emva kweyure e-1 ye-electrolysis, nto leyo enokubangela utshintsho olubi kumandla okubopha e-Ni 2p (jonga iiMifanekiso eziNcedisayo 9 kunye ne-10 ukuze ufumane iinkcukacha ezithe vetshe)26,27,32,33. Ngoko ke, i-NiV-LDH-NS ibonise utshintsho oluncinci kwisakhiwo emva kweyure e-1 ye-COR.
Ukuqinisekisa indima ebalulekileyo ye-V ekukhuthazeni i-COR, senze ii-catalysts ze-NiV-LDH ezine-atomic ratios ezahlukeneyo ze-V:Ni (1:32, 1:16, kunye ne-1:4, ezibizwa ngokuba yi-NiV-32, NiV-16, kunye ne-NiV-4, ngokulandelelana) ngaphandle kwe-1:8 ngendlela efanayo ye-coprecipitation. Iziphumo zemephu ye-EDS zibonisa ukuba i-atomic ratio ye-V:Ni kwi-catalyst isondele kweyomphambili (Umzobo oNcedisayo 11a–e). Ngokunyuka kokuguqulwa kwe-V, amandla e-spectrum ye-V 2p ayanda, kwaye amandla okubopha engingqi ye-Ni 2p aqhubeka etshintsha aye kwicala elingalunganga (Umzobo oNcedisayo 12). Kwangaxeshanye, inani le-OL landa kancinci kancinci. Iziphumo zovavanyo lwe-catalytic zibonisa ukuba i-OER ingacinezelwa ngempumelelo nasemva kokuguqulwa okuncinci kwe-V (umlinganiselo we-atomic we-V:Ni we-1:32), kunye ne-O2 FE yehla ukusuka kwi-27% ukuya kwi-11% kwi-1.8 VRHE emva kokuguqulwa kwe-V (Umfanekiso oNcedisayo we-11f). Ngokunyuka komlinganiselo we-V:Ni ukusuka kwi-1:32 ukuya kwi-1:8, umsebenzi we-catalytic wanda. Nangona kunjalo, ngokunyuka okungakumbi kokuguqulwa kwe-V (umlinganiselo we-V:Ni we-1:4), uxinano lwangoku luyehla, esicinga ukuba lubangelwa kukwehla koxinano lweendawo ezisebenzayo ze-Ni (ingakumbi isigaba esisebenzayo se-NiOOH; Umfanekiso oNcedisayo we-11f). Ngenxa yesiphumo sokukhuthaza sokuguqulwa kwe-V kunye nokugcinwa kweendawo ezisebenzayo ze-Ni, i-catalyst enomlinganiselo we-V:Ni we-1:8 ibonise ukusebenza okuphezulu kwe-FE kunye ne-AA kuvavanyo lokuhlola umlinganiselo we-V:Ni. Ukuze kucaciswe ukuba umlinganiselo we-V:Ni uhlala ungaguquki emva kwe-electrolysis, ukwakheka kwee-catalysts ezisetyenzisiweyo kwachazwa. Iziphumo zibonisa ukuba kwii-catalysts ezine-V:Ni ratios zokuqala ukusuka kwi-1:16 ukuya kwi-1:4, i-V:Ni ratio yehle yaya kwi-1:22 emva kwe-reaction, enokuba ibangelwa kukutsalwa kwe-V ngenxa yokwakhiwa kwakhona kwe-catalyst (Umzobo oNcedisayo 13). Qaphela ukuba ii-AA FEs ezifanayo zibonwe xa i-V:Ni ratio yokuqala yayilingana okanye ingaphezulu kwe-1:16 (Umzobo oNcedisayo 11f), enokuchazwa yi-catalyst reconstruction ekhokelela kwi-V:Ni ratios ezifanayo kwii-catalysts ezibonisa ukusebenza okufanayo kwe-catalytic.
Ukuqinisekisa ngakumbi ukubaluleka kwe-V-modified Ni(OH)2 ekuphuculeni ukusebenza kwe-COR, siphuhlise ezinye iindlela ezimbini zokwenziwa ukuze singenise i-V kwizinto ze-Ni(OH)2-NS. Enye yindlela yokuxuba, kwaye isampuli ibizwa ngokuba yi-NiV-MIX; enye yindlela yokutshiza elandelelanayo, kwaye isampuli ibizwa ngokuba yi-NiV-SP. Iinkcukacha zokwenziwa zibonelelwe kwicandelo leeNdlela. Imephu ye-SEM-EDS ibonise ukuba i-V iguqulwe ngempumelelo kumphezulu we-Ni(OH)2-NS kuzo zombini iisampuli (Umzobo ongezelelweyo 14). Iziphumo ze-electrolysis zibonisa ukuba kwi-1.8 VRHE, ukusebenza kakuhle kwe-AA kwi-electrodes ze-NiV-MIX kunye ne-NiV-SP yi-78% kunye ne-79%, ngokwahlukeneyo, zombini zibonisa ukusebenza kakuhle kune-Ni(OH)2-NS (51%). Ngaphezu koko, i-OER kwi-electrodes ze-NiV-MIX kunye ne-NiV-SP yacinezelwa (FE O2: 7% kunye ne-2%, ngokwahlukeneyo) xa kuthelekiswa ne-Ni(OH)2-NS (FE O2: 27%). Ezi ziphumo ziqinisekisa isiphumo esihle sokuguqulwa kwe-V kwi-Ni(OH)2 ekucinezelweni kwe-OER (Umzobo oNcedisayo 14). Nangona kunjalo, ukuzinza kwee-catalysts kuye kwaphazamiseka, nto leyo eyabonakaliswa kukwehla kwe-FE AA kwi-NiV-MIX ukuya kwi-45% nakwi-NiV-SP ukuya kwi-35% emva kwemijikelo esixhenxe ye-COR, nto leyo ethetha ukuba kufuneka kusetyenziswe iindlela ezifanelekileyo zokuzinzisa iintlobo ze-V, ezifana nokuguqulwa kwe-V kwi-lattice ye-Ni(OH)2 kwi-NiV-LDH-NS, eyi-catalyst ephambili kulo msebenzi.
Sikwavavanye ukuzinza kweNi(OH)2-NS kunye neNiV-LDH-NS ngokufaka i-COR kwimijikelo emininzi. I-reaction yenziwe iyure e-1 ngomjikelo ngamnye kwaye i-electrolyte yatshintshwa emva komjikelo ngamnye. Emva komjikelo wesi-7, ukusebenza kwe-FE kunye ne-AA kwi-Ni(OH)2-NS kwehle ngama-50% kunye nama-60%, ngokulandelanayo, ngelixa ukwanda kwe-OER kwabonwa (Umzobo 2i, j). Emva komjikelo ngamnye, sihlalutye ii-cyclic voltammetry (CV) curves zee-catalysts saza sabona ukuba i-oxidation peak ye-Ni2+ yehla kancinci, nto leyo ebonisa ukwehla kwamandla e-redox e-Ni (Umzobo oNcedisayo 15a–c). Kunye nokwanda koxinzelelo lwe-Nication kwi-electrolyte ngexesha le-electrolysis (Umzobo oNcedisayo 15d), sibandakanya ukuwohloka kokusebenza (ukwehla kwemveliso ye-FE kunye ne-AA) ekutsaleni kwe-Ni kwi-catalyst, okubangela ukutyhileka okukhulu kwe-substrate ene-foam ye-Ni ebonisa umsebenzi we-OER. Ngokwahlukileyo koko, i-NiV-LDH-NS yehlise ukwehla kwemveliso ye-FE kunye ne-AA ukuya kwi-10% (Umzobo 2i, j), nto leyo ebonisa ukuba ukuguqulwa kwe-V kuthintele ngempumelelo i-Ni leaching (Umzobo ongezelelweyo 15d). Ukuze siqonde ukuzinza okuphuculweyo kokuguqulwa kwe-V, senze izibalo zethiyori. Ngokweencwadi zangaphambili34,35, utshintsho lwe-enthalpy lwenkqubo yokususwa kwe-metallization yee-athomu zesinyithi kumphezulu osebenzayo we-catalyst lungasetyenziswa njengenkcazo efanelekileyo yokuvavanya uzinzo lwe-catalyst. Ke ngoko, utshintsho lwe-enthalpy lwenkqubo yokususwa kwe-metallization yee-athomu ze-Ni kumphezulu (100) we-Ni(OH)2-NS eyakhiwe ngokutsha kunye ne-NiV-LDH-NS (i-NiOOH kunye ne-NiVOOH, ngokulandelelana) ziqikelelwe (iinkcukacha zokwakhiwa kwemodeli zichazwe kwiNqaku eliNgezelelweyo 2 kunye noMfanekiso oNgezelelweyo 16). Inkqubo yokususwa kwe-metallization ye-Ni evela kwi-NiOOH kunye ne-NiVOOH ibonisiwe (Umzobo oNgezelelweyo 17). Ixabiso lamandla le-Ni demetallization kwi-NiVOOH (0.0325 eV) liphezulu kunelo le-NiOOH (0.0005 eV), nto leyo ebonisa ukuba ukuguqulwa kwe-V kuphucula uzinzo lwe-NiOOH.
Ukuqinisekisa isiphumo sokuthintela i-OER kwi-NiV-LDH-NS, ngakumbi kwi-anodic potentials ephezulu, i-differential electrochemical mass spectrometry (DEMS) yenziwe ukuze kuphandwe ukwakheka kwe-O2 exhomekeke kwi-potential kwiisampuli ezahlukeneyo. Iziphumo zibonise ukuba xa kungekho cyclohexanone, i-O2 kwi-NiV-LDH-NS yabonakala kwi-potential yokuqala ye-1.53 ​​VRHE, eyayingaphantsi kancinci kune-O2 kwi-Ni(OH)2-NS (1.62 VRHE) (Umzobo oNcedisayo 18). Esi siphumo sibonisa ukuba i-OER inhibition ye-NiV-LDH-NS ngexesha le-COR isenokungabi ngenxa yomsebenzi wayo ophantsi we-OER, ohambelana noxinano oluphezulu kancinci kwi-linear sweep voltammetry (LSV) curves kwi-NiV-LDH-NS kunaleyo kwi-Ni(OH)2-NS ngaphandle kwe-cyclohexanone (Umzobo oNcedisayo 19). Emva kokwaziswa kwe-cyclohexanone, ukuvela kwe-O2 okulibazisekileyo (mhlawumbi ngenxa yenzuzo ye-thermodynamic ye-COR) kuchaza i-FE ephezulu ye-AA kummandla ophantsi we-potential. Okubaluleke ngakumbi, i-OER object potential kwi-NiV-LDH-NS (1.73 VRHE) ilibazisekile ngaphezu kwe-Ni(OH)2-NS (1.65 VRHE), ehambelana ne-FE ephezulu ye-AA kunye ne-FE ephantsi ye-O2 kwi-NiV-LDH-NS kwi-potentials ezintle ngakumbi (Umfanekiso 2c).
Ukuze siqonde ngakumbi isiphumo sokukhuthaza ukuguqulwa kwe-V, sihlalutye i-OER kunye ne-COR reaction kinetics kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS ngokulinganisa iithambeka zazo zeTafel. Kubalulekile ukuqaphela ukuba uxinano lwangoku kummandla weTafel lubangelwa yi-oxidation ye-Ni2+ ukuya kwi-Ni3+ ngexesha lovavanyo lwe-LSV ukusuka kwi-low potential ukuya kwi-high potential. Ukunciphisa isiphumo se-Ni2+ oxidation kumlinganiselo we-COR Tafel slope, siqale sayi-oxidation i-catalyst kwi-1.8 VRHE kangangemizuzu eli-10 saza senza iimvavanyo ze-LSV kwimodi yokuskena engasemva, oko kukuthi, ukusuka kwi-high potential ukuya kwi-low potential (Umfanekiso oNcedisayo 20). I-LSV curve yokuqala yalungiswa nge-100% iR compensation ukuze kufunyanwe i-Tafel slope. Ukuba akukho cyclohexanone, ithambeka likaTafel leNiV-LDH-NS (41.6 mV dec−1) lalingaphantsi kuneleNi(OH)2-NS (65.5 mV dec−1), nto leyo ebonisa ukuba i-OER kinetics inokuphuculwa yi-V modification (Supplementary Fig. 20c). Emva kokungeniswa kwe-cyclohexanone, ithambeka likaTafel leNiV-LDH-NS (37.3 mV dec−1) lalingaphantsi kuneleNi(OH)2-NS (127.4 mV dec−1), nto leyo ebonisa ukuba i-V modification yayinefuthe elicacileyo le-kinetic kwi-COR xa ithelekiswa ne-OER (Supplementary Fig. 20d). Ezi ziphumo zibonisa ukuba nangona i-V modification ikhuthaza i-OER ngandlela ithile, ikhawulezisa kakhulu i-COR kinetics, nto leyo ebangela ukwanda kwe-FE ye-AA.
Ukuze siqonde isiphumo sokukhuthaza sokuguqulwa kwe-V okungentla ekusebenzeni kwe-FE kunye ne-AA, sigxile kwisifundo sendlela yokusebenza. Ezinye iingxelo zangaphambili zibonise ukuba ukuguqulwa kwe-heteroatom kunokunciphisa ubukrelekrele bee-catalysts kwaye kwandise indawo yomphezulu esebenzayo nge-electrochemically (EAS), ngaloo ndlela kwandiswe inani leendawo ezisebenzayo kwaye ngaloo ndlela kuphuculwe umsebenzi we-catalytic36,37. Ukuphanda oku kunokwenzeka, senze imilinganiselo ye-ECSA ngaphambi nasemva kokusebenza kwe-electrochemical, kwaye iziphumo zibonise ukuba i-ECSA ye-Ni(OH)2-NS kunye ne-NiV-LDH-NS yayifana (Umzobo ongezelelweyo 21), ngaphandle kwempembelelo yoxinano lwendawo esebenzayo emva kokuguqulwa kwe-V ekuphuculweni kwe-catalytic.
Ngokolwazi olwamkelweyo ngokubanzi, kwi-electrooxidation ye-Ni(OH)2-catalyzed ye-alcohols okanye ezinye ii-substrates ze-nucleophilic, i-Ni(OH)2 iqala ilahlekelwe zii-electron kunye nee-protons ize incitshiswe ibe yi-NiOOH ngamanyathelo e-electrochemical kwi-anodic potential ethile38,39,40,41. I-NiOOH eyenziweyo emva koko isebenza njengohlobo lwe-COR olusebenzayo lokwenyani ukuya kwi-hydrogen kunye nee-electron ezithathwe kwi-nucleophilic substrate ngamanyathelo eekhemikhali ukwenza i-oxidized product20,41. Nangona kunjalo, kutshanje kuye kwaxelwa ukuba nangona ukunciphisa kwi-NiOOH kunokusebenza njengenyathelo lokumisela izinga (RDS) le-electrooxidation yotywala kwi-Ni(OH)2, njengoko kucetyisiwe kwiincwadi zakutshanje, i-oxidation ye-Ni3+ alcohols inokuba yinkqubo eyenzeka ngokungazenzekiyo ngokudluliselwa kwe-electron engeyiyo i-redox nge-orbitals ezingenamntu ze-Ni3+41,42. Siphefumlelwe luphando lwe-mechanistic olubikwe kwiincwadi ezifanayo, sisebenzise i-dimethylglyoxime disodium salt octahydrate (C4H6N2Na2O2 8H2O) njengemolekyuli ye-probe ukuze sibambe naluphi na ulwakhiwo lwe-Ni2+ oluvela ekunciphiseni kwe-Ni3+ ngexesha le-COR (Umzobo oNcedisayo 22 kunye neNqaku eliNcedisayo 3). Iziphumo zibonise ukwakheka kwe-Ni2+, ziqinisekisa ukuba ukunciphisa kweekhemikhali ze-NiOOH kunye ne-electrooxidation ye-Ni(OH)2 kwenzeke ngaxeshanye ngexesha lenkqubo ye-COR. Ke ngoko, umsebenzi we-catalytic unokuxhomekeka kakhulu kwi-kinetics yokunciphisa kwe-Ni(OH)2 ukuya kwi-NiOOH. Ngokusekelwe kulo mgaqo, siphinde saphanda ukuba ukuguqulwa kwe-V kuya kukhawulezisa ukuncipha kwe-Ni(OH)2 kwaye ngaloo ndlela kuphucule i-COR.
Siqale sasebenzisa iindlela zeRaman ezikwi-situ ukubonisa ukuba iNiOOH yinqanaba elisebenzayo le-COR kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS ngokujonga ukwakheka kwe-NiOOH kwi-potentials ezilungileyo kunye nokusetyenziswa kwayo emva kokungeniswa kwe-cyclohexanone, silandela inkqubo "ye-electrochemical-chemical" ekhankanyiweyo (Umfanekiso 3a). Ngaphezu koko, ukwenziwa kwe-NiV-LDH-NS eyakhiwe ngokutsha kudlule oko kwe-Ni(OH)2-NS, njengoko kungqinwa kukunyamalala okukhawulezileyo kwesignali ye-Ni3+–O Raman. Emva koko sabonisa ukuba i-NiV-LDH-NS ibonise amandla angaphantsi kwe-positive ekwakhiweni kwe-NiOOH xa kuthelekiswa ne-Ni(OH)2-NS xa kukho okanye kungekho i-cyclohexanone (Umfanekiso 3b, c kunye nomfanekiso ongezelelweyo 4c, d). Okuphawulekayo kukuba, ukusebenza okuphezulu kwe-OER ye-NiV-LDH-NS kubangela ukuba amaqamza amaninzi anamathele kwilensi engaphambili yenjongo yokulinganisa iRaman, nto leyo ebangela ukuba incochoyi yeRaman kwi-1.55 VRHE inyamalale (Umzobo oNcedisayo 4d). Ngokweziphumo ze-DEMS (Umzobo oNcedisayo 18), uxinano lwangoku kwi-potentials eziphantsi (i-VRHE < 1.58 ye-Ni(OH)2-NS kunye ne-VRHE < 1.53 ye-NiV-LDH-NS) lubangelwa kakhulu kukwakhiwa kwakhona kwee-ion ze-Ni2+ endaweni ye-OER xa kungekho cyclohexanone. Ngoko ke, incochoyi ye-oxidation ye-Ni2+ kwi-LSV curve inamandla kuneye-NiV-LDH-NS, nto leyo ebonisa ukuba ukuguqulwa kwe-V kunika i-NiV-LDH-NS amandla okuphucula ukuhlaziya (jonga uMfanekiso oNcedisayo 19 ukuze ufumane uhlalutyo oluneenkcukacha).
a I-In situ Raman spectra ye-Ni(OH)2-NS (ekhohlo) kunye ne-NiV-LDH-NS (ekunene) phantsi kweemeko ze-OCP emva kwe-preoxidation kwi-1.5 VRHE kwi-0.5 M KOH kunye ne-0.4 M cyclohexanone kangangemizuzwana engama-60. b I-In situ Raman spectra ye-Ni(OH)2-NS kunye ne-c NiV-LDH-NS kwi-0.5 M KOH + 0.4 M cyclohexanone kwii-potentials ezahlukeneyo. d I-In situ XANES spectra ye-Ni(OH)2-NS kunye ne-NiV-LDH-NS kwi-Ni K-edge kwi-0.5 M KOH kunye ne-e 0.5 M KOH kunye ne-0.4 M cyclohexanone. I-inset ibonisa ummandla we-spectral okhulisiweyo phakathi kwe-8342 kunye ne-8446 eV. f I-Valence states ye-Ni kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS kwii-potentials ezahlukeneyo. g Kwi-Ni situ EXAFS spectra ye-NiV-LDH-NS ngaphambi nasemva kokufakwa kwe-cyclohexanone kwii-potentials ezahlukeneyo. h Iimodeli zethiyori ze-Ni(OH)2-NS kunye ne-NiV-LDH-NS. Phezulu: Kwi-Ni(OH)2-NS, ukuhlaziywa okucothayo ukusuka kwi-Ni(OH)2-NS ukuya kwi-NiOOH kusebenza njenge-RDS, ngelixa i-cyclohexanone inciphisa iintlobo ze-Ni ezi-valent eziphezulu ngamanyathelo eekhemikhali ukugcina imeko ye-Ni e-valent ephantsi ukuvelisa i-AA. Ezantsi: Kwi-NiV-LDH-NS, inyathelo lokuhlaziywa liququzelelwa kukuguqulwa kwe-V, okubangela ukudluliselwa kwe-RDS ukusuka kwinyathelo lokuhlaziywa ukuya kwinyathelo leekhemikhali. i Utshintsho lwamandla asimahla e-Gibbs xa kwakhiwa kwakhona i-Ni(OH)2-NS kunye ne-NiV-LDH-NS. Idatha eluhlaza ye-aj kunye ne-i inikwe kwifayile yedatha eluhlaza.
Ukuze sihlolisise ukuguquka kwezakhiwo zeathomu neze-elektroniki ngexesha lokunciphisa i-catalyst, senze uvavanyo lwe-X-ray absorption spectroscopy (XAS) kwi-situ, olubonelele ngesixhobo esinamandla sokuhlola i-dynamics ye-Ni species ngamanyathelo amathathu alandelelanayo: i-OER, i-cyclohexanone injection, kunye ne-COR kwi-open circuit potential (OCP). Lo mfanekiso ubonisa i-K-edge XANES spectra ye-Ni ene-potential ekhulayo ngaphambi nasemva kwe-cyclohexanone injection (Umfanekiso 3d, e). Kwi-potential efanayo, amandla e-absorption edge e-NiV-LDH-NS angcono kakhulu kunalawo e-Ni(OH)2-NS (Umfanekiso 3d, e, inset). I-valence ephakathi ye-Ni phantsi kwemeko nganye iqikelelwe yi-linear combined fit ye-XANES spectra kunye ne-regression ye-Ni K-edge absorption energy shift (Umfanekiso 3f), kunye ne-reference spectrum ethathwe kwiincwadi ezipapashiweyo (Umfanekiso ongezelelweyo 23)43.
Kwinyathelo lokuqala (ngaphambi kokungeniswa kwe-cyclohexanone, ehambelana nenkqubo ye-OER; Umfanekiso 3f, ekhohlo), kwi-potential ye-catalyst engakhiwanga ngokutsha (<1.3 VRHE), imeko ye-valence ye-Ni kwi-NiV-LDH-NS (+1.83) iphantsi kancinci kune-Ni(OH)2-NS (+1.97), enokuthi ibangelwe kukudluliselwa kwe-electron ukusuka kwi-V ukuya kwi-Ni, ngokuhambelana neziphumo ze-XPS ezikhankanyiweyo apha ngasentla (Umfanekiso 2f). Xa i-potential idlula i-reduction point (1.5 VRHE), imeko ye-valence ye-Ni kwi-NiV-LDH-NS (+3.28) ibonisa ukwanda okucacileyo xa kuthelekiswa ne-Ni(OH)2-NS (+2.49). Kwi-potential ephezulu (1.8 VRHE), imeko ye-valence yamasuntswana e-Ni afunyenwe kwi-NiV-LDH-NS (+3.64) iphezulu kune-Ni(OH)2-NS (+3.47). Ngokweengxelo zakutshanje, le nkqubo ihambelana nokwakheka kweentlobo zeNi4+ ezixineneyo kwisakhiwo seNi3+xOOH1-x (iNi3+x luhlobo oluxutyiweyo lweNi3+ kunye neNi4+), oluye lwabonisa ngaphambili umsebenzi ophucukileyo we-catalytic kwi-alcohol dehydrogenation38,39,44. Ke ngoko, ukusebenza okuphezulu kweNiV-LDH-NS kwi-COR kunokubangelwa kukuncitshiswa okuphuculweyo kokwenza iintlobo zeNi ezixineneyo ezixineneyo.
Kwinyathelo lesibini (ukuqaliswa kwe-cyclohexanone emva kokuvulwa kweringi, Umfanekiso 3f), imeko ye-valence ye-Ni kuzo zombini ii-catalysts yehle kakhulu, nto leyo ehambelana nenkqubo yokunciphisa i-Ni3+xOOH1-x yi-cyclohexanone, ehambelana neziphumo ze-in situ Raman spectroscopy (Umfanekiso 3a), kwaye imeko ye-valence ye-Ni iphantse yabuyela kwimeko yokuqala (inyathelo lokuqala xa iphantsi kwamandla), nto leyo ebonisa ukuguquguquka kwenkqubo ye-redox ye-Ni ukuya kwi-Ni3+xOOH1-x.
Kwinyathelo lesithathu (inkqubo ye-COR) kwi-COR potentials (1.5 kunye ne-1.8 VRHE; Umfanekiso 3f, ekunene), imeko ye-valence ye-Ni kwi-Ni(OH)2-NS inyuke kancinci (+2.16 kunye ne-+2.40), ephantsi kakhulu kune-potential efanayo kwinyathelo lokuqala (+2.49 kunye ne-+3.47). Ezi ziphumo zibonisa ukuba emva kokufakwa kwe-cyclohexanone, i-COR incitshiswa yi-kinetically yi-oxidation ecothayo ye-Ni2+ ukuya kwi-Ni3+x (oko kukuthi, ukwakhiwa kwakhona kwe-Ni) endaweni yenyathelo leekhemikhali phakathi kwe-NiOOH kunye ne-cyclohexanone kwi-Ni(OH)2-NS, eshiya i-Ni kwimeko ye-valence ephantsi. Ke ngoko, sigqiba kwelokuba ukwakhiwa kwakhona kwe-Ni kunokusebenza njenge-RDS kwinkqubo ye-COR kwi-Ni(OH)2-NS. Ngokwahlukileyo koko, i-NiV-LDH-NS igcine i-valence ephezulu ye-Ni species (>3) ngexesha lenkqubo ye-COR, kwaye i-valence yehle kancinci kakhulu (ngaphantsi kwe-0.2) xa kuthelekiswa nenyathelo lokuqala kwi-potential efanayo (1.65 kunye ne-1.8 VRHE), nto leyo ebonisa ukuba ukuguqulwa kwe-V kukhuthaze i-oxidation ye-Ni2+ ukuya kwi-Ni3+x, nto leyo eyenza inkqubo yokunciphisa i-Ni ikhawuleze kunenyathelo lekhemikhali lokunciphisa i-cyclohexanone. Iziphumo zesakhiwo se-extended X-ray absorption fine structure (EXAFS) nazo zityhile utshintsho olupheleleyo lwe-Ni-O (ukusuka kwi-1.6 ukuya kwi-1.4 Å) kunye ne-Ni-Ni(V) (ukusuka kwi-2.8 ukuya kwi-2.4 Å) bonds xa kukho i-cyclohexanone. Oku kuhambelana nokwakhiwa kwakhona kwesigaba se-Ni(OH)2 ukuya kwisigaba se-NiOOH kunye nokunciphisa ikhemikhali kwesigaba se-NiOOH yi-cyclohexanone (Umzobo 3g). Nangona kunjalo, i-cyclohexanone yathintela kakhulu i-kinetics yokunciphisa i-Ni(OH)2-NS (jonga iNqaku elongezelelweyo 4 kunye neFig. elongezelelweyo 24 ukuze ufumane iinkcukacha ezithe vetshe).
Ngokubanzi, kwi-Ni(OH)2-NS (Umzobo 3h, phezulu), inyathelo lokunciphisa kancinci ukusuka kwisigaba se-Ni(OH)2 ukuya kwisigaba se-NiOOH linokusebenza njenge-RDS yenkqubo iyonke ye-COR endaweni yenyathelo lekhemikhali lokwakheka kwe-AA ukusuka kwi-cyclohexanone ngexesha lokunciphisa iikhemikhali ze-NiOOH. Kwi-NiV-LDH-NS (Umzobo 3h, ezantsi), ukuguqulwa kwe-V kuphucula i-oxidation kinetics ye-Ni2+ ukuya kwi-Ni3+x, ngaloo ndlela kukhawulezisa ukwakheka kwe-NiVOOH (endaweni yokusetyenziswa ngokunciphisa iikhemikhali), okutshintshela i-RDS ukuya kwinyathelo lekhemikhali. Ukuze siqonde ukwakhiwa kwakhona kwe-Ni okubangelwa kukuguqulwa kwe-V, senze izibalo ezongezelelweyo zethiyori. Njengoko kubonisiwe kwi-Fig. 3h, silingise inkqubo yokwakha kwakhona ye-Ni(OH)2-NS kunye ne-NiV-LDH-NS. Amaqela e-lattice hydroxyl kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS asuswa ngokukhupha i-OH- kwi-electrolyte ukuze kwenziwe i-lattice oxygen engenazo ii-electron. Iimpendulo zeekhemikhali ezifanelekileyo zezi zilandelayo:
Utshintsho lwamandla asimahla eGibbs lokwakhiwa kwakhona lubalwe (Umfanekiso 3i), kwaye iNiV-LDH-NS (0.81 eV) ibonise utshintsho lwamandla asimahla eGibbs oluncinci kakhulu kuneNi(OH)2-NS (1.66 eV), nto leyo ebonisa ukuba ukuguqulwa kweV kunciphisa i-voltage efunekayo ekwakheni kwakhona iNi. Sikholelwa ukuba ukukhuthaza ukwakhiwa kwakhona kunokunciphisa umqobo wamandla weCOR yonke (jonga uphando lwendlela yokusabela ngezantsi ukuze ufumane iinkcukacha), ngaloo ndlela kukhawuleziswe impendulo kubuninzi bamandla aphezulu.
Uhlalutyo olungasentla lubonisa ukuba ukuguqulwa kwe-V kubangela ukuhlelwa kwakhona kwesigaba okukhawulezayo kwe-Ni(OH)2, ngaloo ndlela kwandisa izinga lokuphendula kwaye, ngokwalo, uxinano lwangoku lwe-COR. Nangona kunjalo, iindawo ze-Ni3+x zinokukhuthaza umsebenzi we-OER. Ukusuka kwi-LSV curve ngaphandle kwe-cyclohexanone, kuyacaca ukuba uxinano lwangoku lwe-NiV-LDH-NS luphezulu kunolo lwe-Ni(OH)2-NS (Umzobo oNcedisayo 19), obangela ukuba iimpendulo ze-COR kunye ne-OER zenze iimpendulo ezikhuphisanayo. Ke ngoko, i-FE ephezulu kakhulu ye-AA kune-NiV-LDH-NS ayinakuchazwa ngokupheleleyo ngokuguqulwa kwe-V okukhuthaza ukuhlelwa kwakhona kwesigaba.
Kuyavunywa ngokubanzi ukuba kwi-alkaline media, ii-electrooxidation reactions ze-nucleophilic substrates zihlala zilandela imodeli yeLangmuir–Hinshelwood (LH). Ngokukodwa, i-substrate kunye ne-OH− anions zidityaniswa ngokukhuphisana kumphezulu we-catalyst, kwaye i-OH− efakwe kwi-adsorbed i-oxidized ukuya kumaqela e-hydroxyl asebenzayo (OH*), asebenza njengee-electrophiles ze-oxidation ye-nucleophiles, indlela ebonakaliswe ngaphambili yidatha yovavanyo kunye/okanye ukubalwa kwethiyori45,46,47. Ke ngoko, ukuxinana kwee-reactants kunye nomlinganiselo wazo (i-organic substrate kunye ne-OH−) kunokulawula ukugqunywa kwe-reactant kumphezulu we-catalyst, ngaloo ndlela kuchaphazela i-FE kunye nemveliso yemveliso ekujoliswe kuyo14,48,49,50. Kwimeko yethu, sicinga ukuba ukugqunywa okuphezulu kwe-cyclohexanone kumphezulu kwi-NiV-LDH-NS kuthanda inkqubo ye-COR, kwaye ngokuchaseneyo, ukugqunywa okuphantsi kwe-cyclohexanone kumphezulu kwi-Ni(OH)2-NS kuthanda inkqubo ye-OER.
Ukuvavanya le ngcamango ingasentla, siqale senza uthotho lwezilingo ezimbini ezinxulumene noxinzelelo lwee-reactants (C, cyclohexanone, kunye ne-COH−). Uvavanyo lokuqala lwenziwe nge-electrolysis kwi-constant potential (1.8 VRHE) kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS catalysts ezine-cyclohexanone C contents ezahlukeneyo (0.05 ~ 0.45 M) kunye nomxholo we-COH− osisigxina (0.5 M). Emva koko, imveliso ye-FE kunye ne-AA ibalwe. Kwi-catalyst ye-NiV-LDH-NS, ubudlelwane phakathi kwe-AA yield kunye ne-cyclohexanone C bubonise i-curve eqhelekileyo "yohlobo lwentaba-mlilo" kwimodi ye-LH (Umzobo 4a), nto leyo ebonisa ukuba ukugubungela okuphezulu kwe-cyclohexanone kukhuphisana ne-OH− adsorption. Ngelixa kwi-Ni(OH)2-NS, isivuno se-AA sanda ngokungaqhelekanga ngokunyuka kwe-C ye-cyclohexanone ukusuka kwi-0.05 ukuya kwi-0.45 M, okubonisa ukuba nangona uxinzelelo olukhulu lwe-cyclohexanone lwaluphezulu (0.45 M), ukugubungela kwayo umphezulu kwakusephantsi. Ukongeza, ngokunyuka kwe-COH− ukuya kwi-1.5 M, i-"type type volcanic" curve yabonwa kwi-Ni(OH)2-NS ngokuxhomekeke kwi-C ye-cyclohexanone, kwaye i-inflection point yokusebenza yalibaziseka xa ithelekiswa ne-NiV-LDH-NS, nto leyo ebonisa ngakumbi ukungenwa kwe-cyclohexanone kwi-Ni(OH)2-NS (Umzobo oNcedisayo 25a kunye neNqaku 5). Ukongeza, i-FE ye-AA kwi-NiV-LDH-NS yayinovelwano kakhulu kwi-C-cyclohexanone kwaye yanda ngokukhawuleza yaya ngaphezulu kwe-80% xa i-C-cyclohexanone yonyuswa ukusuka kwi-0.05 M ukuya kwi-0.3 M, nto leyo ebonisa ukuba i-cyclohexanone yayityebiswe lula kwi-NiV-LDH-NS (Umfanekiso 4b). Ngokwahlukileyo koko, ukonyusa uxinzelelo lwe-C-cyclohexanone akuzange kuyithintele kakhulu i-OER kwi-Ni(OH)2-NS, enokubangelwa kukungafakwa ngokwaneleyo kwe-cyclohexanone. Ngokwahlukileyo koko, uphando olongezelelweyo lokuxhomekeka kwe-COH− ekusebenzeni kakuhle kwe-catalytic luqinisekisile ukuba ukutsalwa kwe-cyclohexanone kuphuculwe xa kuthelekiswa ne-NiV-LDH-NS, enokunyamezela i-COH− ephezulu ngexesha lenkqubo ye-COR ngaphandle kokunciphisa i-FE ye-AA (Umfanekiso ongezelelweyo 25b, c kunye neNqaku 5).
Imveliso ye-AA kunye ne-EF ye-b Ni(OH)2-NS kunye ne-NiV-LDH-NS kwi-cyclohexanone ene-C eyahlukileyo kwi-0.5 M KOH. c Amandla okufunxa i-cyclohexanone kwi-NiOOH kunye ne-NiVOOH. d I-FE ye-AA kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS kwi-0.5 M KOH kunye ne-0.4 M cyclohexanone kwi-1.80 VRHE kusetyenziswa amaqhinga okungakwazi ukuqhubeka nokungaguquki. Iibha zempazamo zimele ukuphambuka okuqhelekileyo kwemilinganiselo emithathu ezimeleyo kusetyenziswa isampuli efanayo kwaye zingaphakathi kwe-10%. e Phezulu: Kwi-Ni(OH)2-NS, i-cyclohexanone enendawo ephantsi yomphezulu C ifunxwa kancinci yi-cyclohexanone, nto leyo ebangela ukhuphiswano olunamandla lwe-OER. Ezantsi: Kwi-NiV-LDH-NS, ukuxinana okuphezulu komphezulu we-cyclohexanone C kubonwa ngokufunxwa okwandisiweyo kwe-cyclohexanone, nto leyo ebangela ukucinywa kwe-OER. Idatha eluhlaza ye-a–d inikwe kwifayile yedatha eluhlaza.
Ukuvavanya ukunyuswa kwe-cyclohexanone kwi-NiV-LDH-NS, sisebenzise i-electrochemical coupled quartz crystal microbalance (E-QCM) ukujonga utshintsho olukhulu lweentlobo ezifakwe kwi-NiV-LDH-NS ngexesha langempela. Iziphumo zibonise ukuba amandla okuqala okufunxa i-cyclohexanone kwi-NiV-LDH-NS ayemakhulu ngokuphindwe kayi-1.6 kunalawo akwi-Ni(OH)2-NS kwimeko ye-OCP, kwaye lo mahluko kumandla okufunxa i-adsorption wanda ngakumbi njengoko amandla enyuka ukuya kwi-1.5 VRHE (Umzobo oNcedisayo 26). Ubalo lwe-DFT olujikelezisiweyo lwenziwe ukuphanda indlela yokuziphatha kwe-cyclohexanone kwi-NiOOH nakwi-NiVOOH (Umfanekiso 4c). I-Cyclohexanone ingena kwi-Ni-center kwi-NiOOH ngamandla okufunxa (ii-Eads) angama--0.57 eV, ngelixa i-cyclohexanone inokufunxa kwi-Ni-center okanye kwi-V-center kwi-NiVOOH, apho i-V-center inika ii-Eads eziphantsi kakhulu (-0.69 eV), ngokuhambelana nokufunxa okubonakalayo okunamandla kwe-cyclohexanone kwi-NiVOOH.
Ukuqinisekisa ngakumbi ukuba ukunyuswa okuphuculweyo kwe-cyclohexanone kunokukhuthaza ukwakheka kwe-AA kwaye kuthintele i-OER, sisebenzise icebo le-discontinuous potential ukutyebisa i-cyclohexanone kumphezulu we-catalyst (kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS), elaphefumlelwa ziingxelo zangaphambili. 51, 52 Ngokukodwa, sisebenzise i-potential ye-1.8 VRHE kwi-COR, emva koko sayitshintshela kwi-OCP state, saza sayitshintshela kwi-1.8 VRHE. Kule meko, i-cyclohexanone inokuqokelelana kumphezulu we-catalyst kwi-OCP state phakathi kwe-electrolyses (jonga icandelo leeNdlela ukuze ufumane iinkqubo ezineenkcukacha). Iziphumo zibonise ukuba kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS, ukusebenzisa i-discontinuous potential electrolysis kuphucule ukusebenza kwe-catalytic xa kuthelekiswa ne-constant potential electrolysis (Umfanekiso 4d). Okuphawulekayo kukuba, i-Ni(OH)2-NS ibonise ukuphucuka okubalulekileyo kwi-COR (AA FE: ukusuka kwi-51% ukuya kwi-82%) kunye nokuncitshiswa kwe-OER (O2 FE: ukusuka kwi-27% ukuya kwi-4%) kune-NiV-LDH-NS, nto leyo eyabangelwa kukuba ukuqokelelwa kwe-cyclohexanone kunokuphuculwa kakhulu kwi-catalyst enekhono elibuthathaka lokutsalwa kwe-adsorption (oko kukuthi, i-Ni(OH)2-NS) nge-extractive potential electrolysis.
Ngokubanzi, ukuthintelwa kwe-OER kwi-NiV-LDH-NS kunokubangelwa kukunyuswa kwe-cyclohexanone (Umfanekiso 4e). Kwi-Ni(OH)2-NS (Umfanekiso 4e, phezulu), ukunyuswa okubuthathaka kwe-cyclohexanone kubangele ukugutyungelwa kwe-cyclohexanone okuphantsi kunye nokugutyungelwa kwe-OH* okuphezulu kumphezulu we-catalyst. Ke ngoko, iintlobo ze-OH* ezingaphezulu ziya kukhokelela kukhuphiswano olukhulu lwe-OER kwaye zinciphise i-FE ye-AA. Ngokwahlukileyo koko, kwi-NiV-LDH-NS (Umfanekiso 4e, ezantsi), ukuguqulwa kwe-V kwandisa amandla okunyuswa kwe-cyclohexanone, ngaloo ndlela kwandisa umphezulu we-C we-cyclohexanone kwaye kusetyenziswe ngempumelelo iintlobo ze-OH* ezifakwe kwi-COR, kukhuthaza ukwakheka kwe-AA kunye nokuthintela i-OER.
Ukongeza ekuphononongeni impembelelo yokuguqulwa kwe-V ekwakhiweni kwakhona kweentlobo ze-Ni kunye nokunyuswa kwe-cyclohexanone, sikwaphande nokuba i-V iyayitshintsha na indlela yokwakheka kwe-AA ukusuka kwi-COR. Iindlela ezahlukeneyo ze-COR ziye zacetyiswa kwiincwadi, kwaye sihlalutye amathuba azo kwinkqubo yethu yokusabela (jonga uMzobo oNcedisayo 27 kunye neNqaku eliNcedisayo 6 ukuze ufumane iinkcukacha ezithe vetshe)13,14,26. Okokuqala, kuye kwaxelwa ukuba inyathelo lokuqala lendlela ye-COR linokubandakanya i-oxidation yokuqala ye-cyclohexanone ukwenza i-key intermediate 2-hydroxycyclohexanone (2)13,14. Ukuqinisekisa inkqubo, sisebenzise i-5,5-dimethyl-1-pyrrolidine N-oxide (DMPO) ukubamba ii-intermediate ezisebenzayo ezifakwe kumphezulu we-catalyst kwaye safunda i-EPR. Iziphumo ze-EPR zityhile ubukho be-radicals ezigxile kwi-C (R) kunye ne-hydroxyl radicals (OH) kuzo zombini ii-catalysts ngexesha lenkqubo ye-COR, nto leyo ebonisa ukuba i-Cα − H dehydrogenation ye-cyclohexanone yenza i-radical ephakathi ye-enolate (1), ethi emva koko i-oxidized yi-OH* ukuze yenze i-2 (Umzobo 5a kunye nomzobo ongezelelweyo 28). Nangona ii-intermediates ezifanayo zichongiwe kuzo zombini ii-catalysts, i-area fraction yesignali ye-R kwi-NiV-LDH-NS yayiphezulu kuneye-Ni(OH)2-NS, enokuba ibangelwa kukwanda kwamandla okunyuswa kwe-cyclohexanone (Itheyibhile eyongezelelweyo 3 kunye neNqaku 7). Sisebenzise kwakhona i-2 kunye ne-1,2-cyclohexanedione (3) njengee-reactants zokuqala ze-electrolysis ukuvavanya ukuba i-V iya kutshintsha na inyathelo elilandelayo le-oxidation. Iziphumo ze-electrolysis ze-potential intermediates (2 kunye ne-3) kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS zibonise ukukhethwa kwemveliso okufanayo, nto leyo ebonisa ukuba i-COR reaction kwi-Ni(OH)2-NS okanye kwi-NiV-LDH-NS iqhubekile ngeendlela ezifanayo (Umfanekiso 5b). Ngaphezu koko, i-AA yayiyimveliso ephambili kuphela xa i-2 isetyenziswa njenge-reactant, nto leyo ebonisa ukuba i-AA ifunyenwe ngenkqubo ye-oxidation ethe ngqo ngokuqhekeka kwe-Cα − Cβ bond ye-2 endaweni ye-oxidation elandelayo kwi-3 kuzo zombini ii-catalysts, kuba yaguqulwa kakhulu kwi-GA xa i-3 isetyenziswa njenge-reactant yokuqala (Imifanekiso eyongezelelweyo 29, 30).
Isignali ye-EPR ye-NiV-LDH-NS kwi-0.5 M KOH + 0.4 M cyclohexanone. b Iziphumo zohlalutyo lwe-electrocatalytic lwe-2-hydroxycyclohexanone (2) kunye ne-1,2-cyclohexanedione (3). I-Electrolysis yenziwe kwi-0.5 M KOH kunye ne-0.1 M 2 okanye 3 kwi-1.8 VRE iyure enye. Iibha zempazamo zimele ukuphambuka okuqhelekileyo kwemilinganiselo emibini ezimeleyo kusetyenziswa i-catalyst efanayo. c Iindlela zokusabela ezicetywayo ze-COR kwii-catalysts ezimbini. d Umzobo we-Schematic wendlela ye-COR kwi-Ni(OH)2-NS (ekhohlo) kunye ne-d NiV-LDH-NS (ekunene). Iintolo ezibomvu zibonisa amanyathelo akhuthazwa luhlengahlengiso lwe-V kwinkqubo ye-COR. Idatha eluhlaza ye-a kunye ne-b ibonelelwa kwifayile yedatha eluhlaza.
Lilonke, sibonise ukuba i-Ni(OH)2-NS kunye ne-NiV-LDH-NS zivuselela i-COR ngendlela efanayo: i-cyclohexanone ifunxwa kumphezulu we-catalyst, ikhutshwe i-hydrogen kwaye ilahlekelwe zii-electron ukuze yenze i-1, ethi emva koko i-OH* ifunxwe yi-2, ilandelwe ziinguqu ezininzi ukuvelisa i-AA (Umfanekiso 5c). Nangona kunjalo, xa i-cyclohexanone isetyenziswa njenge-reactant, ukhuphiswano lwe-OER lwabonwa kuphela kwi-Ni(OH)2-NS, ngelixa inani elincinci le-oxygen laqokelelwa xa i-2 kunye ne-3 zasetyenziswa njenge-reactants. Ke ngoko, umahluko obonweyo ekusebenzeni kwe-catalytic unokubangelwa lutshintsho kumqobo wamandla we-RDS kunye nomthamo we-cyclohexanone adsorption obangelwa kukuguqulwa kwe-V endaweni yotshintsho kwindlela yokusabela. Ke ngoko sihlalutye i-RDS yeendlela zokusabela kuzo zombini ii-catalysts. Iziphumo ze-X-ray acoustic spectroscopy ezikhankanyiweyo apha ngasentla zibonisa ukuba ukuguqulwa kwe-V kutshintsha i-RDS kwi-COR reaction ukusuka kwinqanaba lokwakha kwakhona ukuya kwinqanaba leekhemikhali, kugcina isigaba se-NiOOH kunye neentlobo ze-Ni eziphezulu zingasebenzi kwi-NiV-LDH-NS (Umzobo 3f, Umfanekiso ongezelelweyo 24, kunye neNqaku 4). Sihlalutye ngakumbi iinkqubo zempendulo ezimelwe yi-current density kwicandelo ngalinye leendawo ezahlukeneyo ezinokubakho ngexesha lokulinganisa i-CV (jonga Umfanekiso ongezelelweyo 31 kunye neNqaku 8 ngeenkcukacha) kwaye senze uvavanyo lwe-H/D kinetic isotope exchange, oluye lwabonisa ngokudibeneyo ukuba i-RDS ye-COR kwi-NiV-LDH-NS ibandakanya ukuqhekeka kwe-Cα − H bond kwinqanaba leekhemikhali kunenqanaba lokunciphisa (jonga Umfanekiso ongezelelweyo 32 kunye neNqaku 8 ngeenkcukacha ezithe vetshe).
Ngokusekelwe kuhlalutyo olungentla, isiphumo siphela sokuguqulwa kwe-V siboniswe kuMfanekiso 5d. Ii-catalysts ze-Ni(OH)2-NS kunye ne-NiV-LDH-NS zenzeka ukwakhiwa kwakhona komphezulu kwi-anodic potentials ephezulu kwaye zivuselela i-COR ngendlela efanayo. Kwi-Ni(OH)2-NS (Umfanekiso 5d, ekhohlo), inyathelo lokwakhiwa kwakhona yi-RDS ngexesha lenkqubo ye-COR; ngelixa kwi-NiV-LDH-NS (Umfanekiso 5d, ekunene), ukuguqulwa kwe-V kwakhawulezisa kakhulu inkqubo yokwakha kwakhona kwaye kwaguqula i-RDS yaba yi-Cα−H dehydrogenation ye-cyclohexanone ukuze ibe yi-1. Ukongeza, ukutsalwa kwe-cyclohexanone kwenzeke kwindawo ye-V kwaye kwaphuculwa kwi-NiV-LDH-NS, eyaba negalelo ekucinezelweni kwe-OER.
Ukuqwalasela ukusebenza kakuhle kwe-electrocatalytic ye-NiV-LDH-NS ene-FE ephezulu kuluhlu olubanzi lwamandla, siyile i-MEA ukuze sifezekise imveliso eqhubekayo ye-AA. I-MEA yahlanganiswa kusetyenziswa i-NiV-LDH-NS njenge-anode, i-PtRu/C yorhwebo njenge-cathode53 kunye ne-anion exchange membrane (uhlobo: FAA-3-50) (Umfanekiso 6a kunye nomfanekiso ongezelelweyo 33)54. Ekubeni i-voltage yeseli yehlile kwaye i-FE ye-AA yayifana ne-0.5 M KOH kwisifundo esingentla, uxinzelelo lwe-anolyte lwalungiswa ukuya kwi-1 M KOH (Umfanekiso ongezelelweyo 25c). Ii-LSV curves ezirekhodiweyo ziboniswe kwi-Supplementary Fig. 34, ebonisa ukuba ukusebenza kwe-COR kwe-NiV-LDH-NS kuphezulu kakhulu kune-Ni(OH)2-NS. Ukubonisa ukongama kweNiV-LDH-NS, i-electrolysis yamandla aqhubekayo yenziwe nge-step current density ukusuka kwi-50 ukuya kwi-500 mA cm−2 kwaye i-voltage yeseli ehambelanayo yarekhodwa. Iziphumo zibonise ukuba iNiV-LDH-NS ibonise i-voltage yeseli ye-1.76 V kwi-current density ye-300 mA cm−2, eyayingaphantsi nge-16% kuneyeNi(OH)2-NS (2.09 V), nto leyo ebonisa ukusebenza kwayo kwamandla aphezulu kwimveliso ye-AA (Umzobo 6b).
Umzobo weskematiki webhetri yokuhamba. b I-voltage yeseli ngaphandle kwembuyekezo ye-iR kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS kwi-1 M KOH kunye ne-0.4 M cyclohexanone kwiidensities ezahlukeneyo zangoku. c I-AA kunye ne-FE ziyavelisa kwi-Ni(OH)2-NS kunye ne-NiV-LDH-NS kwiidensities ezahlukeneyo zangoku. Iibha zempazamo zimele ukuphambuka okuqhelekileyo kwemilinganiselo emibini ezimeleyo kusetyenziswa i-catalyst efanayo. d Uthelekiso lokusebenza kwe-catalytic yomsebenzi wethu kunye nezinye iinkqubo zebhetri yokuhamba ezixeliweyo14,17,19. Iiparameter zempendulo kunye neempawu zempendulo zidweliswe ngokweenkcukacha kwiTheyibhile eyoNgezelelweyo 2. e I-voltage yeseli kunye ne-FE ye-AA kwi-NiV-LDH-NS kwi-200 kunye ne-300 mA cm−2 kuvavanyo lwexesha elide, ngokwahlukeneyo. Idatha eluhlaza ye-be inikezelwa njengefayile yedatha eluhlaza.
Okwangoku, njengoko kubonisiwe kwiFig. 6c, i-NiV-LDH-NS ngokusisiseko igcine i-FE elungileyo (83% ukuya kwi-61%) kuxinano oluphezulu lwamandla ombane (200 ukuya kwi-500 mA cm-2), ngaloo ndlela iphucula imveliso ye-AA (1031 ukuya kwi-1900 μmol cm-2 h-1). Okwangoku, yi-0.8% kuphela yee-anions ze-adipic acid ezibonwe kwindawo ye-cathode emva kwe-electrolysis, nto leyo ebonisa ukuba utshintsho lwe-cyclohexanone aluzange lubaluleke kwimeko yethu (Umzobo Ongezelelweyo 35). Ngokwahlukileyo koko, ngesantya esifanayo sokwanda koxinano lwamandla ombane, i-FE ye-AA kwi-Ni(OH)2-NS yehle ukusuka kwi-61% ukuya kwi-34%, nto leyo eyenza kwaba nzima ukuphucula imveliso ye-AA (762 ukuya kwi-1050 μmol cm-2 h-1). Ngokukodwa, ukusebenza kwe-AA kwehle kancinci ngenxa yokhuphiswano olunamandla oluvela kwi-OER, kwaye ngaloo ndlela i-FE ye-AA yehle kakhulu ngokonyuka koxinano lwangoku (ukusuka kwi-200 ukuya kwi-250 mA cm−2, umzobo ongezelelweyo 5). Ngokolwazi lwethu, iziphumo ze-catalytic ezisebenzisa i-MEA kunye nee-catalysts ze-NiV-LDH-NS zidlula kakhulu ukusebenza kwee-reactors zokuhamba ezixeliweyo ngaphambili ezinee-catalysts ezisekelwe kwi-Ni (Itheyibhile eyoNgezelelweyo 2). Ngaphezu koko, njengoko kubonisiwe kumzobo 6d, i-NiV-LDH-NS ibonise iingenelo ezibalulekileyo ngokubhekiselele kuxinano lwangoku, i-voltage yeseli, kunye ne-FE ye-AA xa kuthelekiswa ne-catalyst esekwe kwi-Co esebenza kakuhle, oko kukuthi, i-Co3O4 exhaswa yi-graphene (Co3O4/GDY)17. Ukongeza, sivavanye ukusetyenziswa kwamandla kwimveliso ye-AA saza sabonisa ukuba ukusetyenziswa kwe-AA bekuphantsi kakhulu, yi-2.4 W h gAA-1 kuphela kwi-current density ye-300 mA cm-2 kunye ne-voltage yeseli ye-1.76 V (izibalo ezineenkcukacha zibonelelwe kwiNqaku elongezelelweyo 1). Xa kuthelekiswa nesiphumo esingcono se-4.1 W h gAA-1 ye-Co3O4/GDY echazwe ngaphambili, ukusetyenziswa kwamandla kwimveliso ye-AA emsebenzini wethu kuncitshiswe yi-42% kwaye imveliso yonyuswe ngamaxesha ama-4 (1536 vs. 319 μmol cm-2 h-1)17.
Uzinzo lwe-catalyst ye-NiV-LDH-NS yokuveliswa kwe-AA yexesha elide kwi-MEA luvavanywe kuxinano lwangoku lwe-200 kunye ne-300 mA cm-2, ngokulandelanayo (Umfanekiso 6e). Ekubeni i-OH− isetyenziswa ngokukhawuleza kuxinano lwangoku oluphezulu, izinga lokuvuselelwa kwe-electrolyte kwi-300 mA cm-2 liphezulu kunelo likwi-200 mA cm-2 (jonga icandelo elithi "Ukulinganiswa kwe-Electrochemical" ukuze ufumane iinkcukacha). Kuxinano lwangoku lwe-200 mA cm-2, ukusebenza kakuhle kwe-COR okuqhelekileyo kwakuyi-93% kwiiyure ezi-6 zokuqala, emva koko kwehla kancinci ukuya kwi-81% emva kweeyure ezingama-60, ngelixa i-voltage yeseli inyuke kancinci nge-7% (ukusuka kwi-1.62 V ukuya kwi-1.73 V), nto leyo ebonisa uzinzo oluhle. Njengoko uxinano lwangoku lusanda ukuya kwi-300 mA cm−2, ukusebenza kakuhle kwe-AA kuhlala kungatshintshanga (kwehla ukusuka kwi-85% ukuya kwi-72%), kodwa i-voltage yeseli inyuke kakhulu (ukusuka kwi-1.71 ukuya kwi-2.09 V, ehambelana ne-22%) ngexesha lovavanyo lweeyure ezingama-46 (Umfanekiso 6e). Sicinga ukuba isizathu esiphambili sokuwohloka kokusebenza kukubola kwe-anion exchange membrane (AEM) yi-cyclohexanone, okukhokelela ekwandeni kokumelana kweseli kunye ne-voltage yeseli ye-electrolyzer (Umfanekiso oNcedisayo 36), okuhambisana nokuvuza okuncinci kwe-electrolyte ukusuka kwi-anode ukuya kwi-cathode, okubangela ukwehla komthamo we-anolyte kunye nesidingo sokumisa i-electrolysis. Ukongeza, ukwehla kwe-FE ye-AA kunokubangelwa kukutsalwa kwee-catalysts, okukhuthaza ukuvulwa kwe-Ni foam ye-OER. Ukubonisa impembelelo ye-AEM ebolileyo ekuwohlokeni kozinzo kwi-300 mA cm−2, siyitshintshile nge-AEM entsha emva kweeyure ezingama-46 ze-electrolysis. Njengoko bekulindelekile, ukusebenza kakuhle kwe-catalytic kwabuyiselwa ngokucacileyo, kunye ne-voltage yeseli yehla kakhulu ukuya kwixabiso lokuqala (ukusuka kwi-2.09 ukuya kwi-1.71 V) yaza yanda kancinci ngexesha leeyure ezili-12 ezilandelayo ze-electrolysis (ukusuka kwi-1.71 ukuya kwi-1.79 V, ukunyuka kwe-5%; Umfanekiso 6e).
Lilonke, sikwazile ukufikelela kwiiyure ezingama-60 zokuzinza kwemveliso ye-AA eqhubekayo kuxinano lwangoku lwe-200 mA cm−2, nto leyo ebonisa ukuba i-FE kunye ne-voltage yeseli ye-AA zigcinwa kakuhle. Sizame noxinano lwangoku oluphezulu lwe-300 mA cm−2 saza safikelela kuzinzo lwangoku lwe-58 h, sathatha indawo ye-AEM entsha emva kweeyure ezingama-46. Izifundo ezingasentla zibonisa uzinzo lwe-catalyst kwaye zibonisa ngokucacileyo imfuneko yophuhliso lwexesha elizayo lwe-AEMs ezinamandla aphezulu ukuphucula uzinzo lwexesha elide lwe-MEA kwimveliso ye-AA eqhubekayo kuxinano lwangoku olufanelekileyo kwimizi-mveliso.
Ngokusekelwe ekusebenzeni kwe-MEA yethu, sicebise inkqubo epheleleyo yemveliso ye-AA equka ukondla i-substrate, i-electrolysis, i-neutralization, kunye neeyunithi zokwahlula (Umfanekiso oNcedisayo 37). Uhlalutyo lokuqala lokusebenza lwenziwe ukuvavanya ukuba kunokwenzeka na inkqubo kusetyenziswa imodeli yemveliso ye-alkaline electrocatalytic carboxylate55. Kule meko, iindleko ziquka imali, imisebenzi, kunye nezixhobo (Umfanekiso 7a kunye nomfanekiso oNcedisayo 38), kwaye ingeniso ivela kwimveliso ye-AA kunye ne-H2. Iziphumo ze-TEA zibonisa ukuba phantsi kweemeko zethu zokusebenza (ubuninzi bangoku obuyi-300 mA cm-2, i-voltage yeseli eyi-1.76 V, i-FE 82%), iindleko zizonke kunye nengeniso yi-US $2429 kunye ne-US $2564, ngokwahlukeneyo, nto leyo eguqulela kwinzuzo eyi-US $135 ngetoni ye-AA eveliswayo (jonga iNqaku eliNcedisayo 9 ukuze ufumane iinkcukacha).
a Ixabiso lilonke lenkqubo ye-electrochemical ye-AA phantsi kwemeko yesiseko kunye ne-FE ye-82%, uxinano lwangoku lwe-300 mA cm−2, kunye ne-voltage yeseli ye-1.76 V. Uhlalutyo lovakalelo lweendleko ezintathu ukuya kwi-b FE kunye ne-c current density. Kuhlalutyo lovakalelo, kuphela iiparameter ezifundweyo ezahlukanisiweyo kwaye ezinye iiparameter zigcinwe zingaguquki ngokusekelwe kwimodeli ye-TEA. d Iziphumo ze-FE ezahlukeneyo kunye noxinano lwangoku kwinzuzo ye-electrosynthesis ye-AA kunye nenzuzo kusetyenziswa i-Ni(OH)2-NS kunye ne-NiV-LDH-NS, kucingelwa ukuba i-voltage yeseli igcinwa ingaguquki kwi-1.76 V. Idatha yokufaka ye-a–d inikwe kwifayile yedatha eluhlaza.
Ngokusekelwe kwesi sizathu, siqhubele phambili ngophando ngempembelelo ye-FE kunye noxinano lwangoku kwinzuzo ye-AA electrosynthesis. Sifumanise ukuba inzuzo ibuthathaka kakhulu kwi-FE ye-AA, kuba ukwehla kwe-FE kukhokelela ekunyukeni okukhulu kweendleko zokusebenza, ngaloo ndlela kunyusa kakhulu iindleko zizonke (Umfanekiso 7b). Ngokuphathelele uxinano lwangoku, uxinano lwangoku oluphezulu (>200 mA cm-2) lunceda ukunciphisa iindleko zemali kunye neendleko zokwakha izityalo, ikakhulu ngokunciphisa indawo yeseli ye-electrolytic, ngaloo ndlela negalelo ekwandeni kwenzuzo (Umfanekiso 7c). Xa kuthelekiswa noxinano lwangoku, i-FE inempembelelo enkulu kwinzuzo. Ngokuchaza impembelelo ye-FE kunye noxinano lwangoku kwinzuzo, sibona ngokucacileyo ukubaluleka kokufikelela kwi-FE ephezulu (>60%) kuxinano lwangoku olufanelekileyo kwimizi-mveliso (>200 mA cm-2) ukuqinisekisa inzuzo. Ngenxa yexabiso eliphezulu le-FE le-AA, inkqubo yokusabela ene-NiV-LDH-NS njenge-catalyst ihlala ilungile kuluhlu lwe-100–500 mA cm−2 (amachaphaza e-pentagram; Umfanekiso 7d). Nangona kunjalo, kwi-Ni(OH)2-NS, ukunciphisa i-FE kuxinano oluphezulu lwamandla ombane (>200 mA cm−2) kukhokelele kwiziphumo ezingalunganga (izangqa; Umfanekiso 7d), nto leyo egxininisa ukubaluleka kwee-catalysts ezine-FE ephezulu kuxinano oluphezulu lwamandla ombane.
Ukongeza ekubalulekeni kwezinto ezibangela ukonakala kwezakhamzimba ekunciphiseni iindleko zemali kunye nezokusebenza, uvavanyo lwethu lwe-TEA lubonisa ukuba inzuzo ingaphuculwa ngakumbi ngeendlela ezimbini. Eyokuqala kukuthengisa kunye i-potassium sulfate (K2SO4) kwimarike njengemveliso ephuma kwiyunithi yokunganyakazi, kodwa ngengeniso enokubakho ye-US$828/t AA-1 (Inqaku elongezelelweyo 9). Eyesibini kukuphucula itekhnoloji yokucubungula, kubandakanya ukuphinda kusetyenziswe izinto okanye uphuhliso lwetekhnoloji yokwahlula i-AA engabizi kakhulu (ezinye iindlela zokwahlula i-AA kunye neeyunithi zokwahlula). Inkqubo yokunganyakazi kwe-acid-base esetyenziswayo ngoku inokubangela iindleko eziphezulu zezinto (ezibangela isabelo esikhulu kwi-85.3%), apho i-94% yazo ibangelwa yi-cyclohexanone kunye ne-KOH ($2069/t AA-1; Umfanekiso 7a), kodwa njengoko kukhankanyiwe ngasentla, inkqubo isenenzuzo iyonke. Sicebisa ukuba iindleko zezinto ezibonakalayo zingancitshiswa ngakumbi ngeendlela eziphucukileyo zokubuyisela i-KOH kunye ne-cyclohexanone engaphendulwanga, ezifana ne-electrodialysis yokubuyisela ngokupheleleyo i-KOH14 (ixabiso eliqikelelweyo le-US$1073/t AA-1 nge-electrodialysis; Inqaku elongezelelweyo 9).
Ngamafutshane, sifikelele ekusebenzeni kakuhle kwe-electrolysis yeathomu ye-aluminiyam kwi-high current density ngokufaka i-V kwi-nanosheets ze-Ni(OH)2. Phantsi koluhlu olubanzi lwe-1.5–1.9 VRHE kunye ne-high current density ye-170 mA cm−2, i-AA FE kwi-NiV-LDH-NS ifikelele kwi-83–88%, ngelixa i-OER yancitshiswa ngempumelelo ukuya kwi-3%. Ukuguqulwa kwe-V kukhuthaze ukwehla kwe-Ni2+ ukuya kwi-Ni3+x kwaye kwaphucula ukutsalwa kwe-cyclohexanone. Idatha yovavanyo kunye neyethiyori ibonisa ukuba ukwakhiwa kwakhona okuvuselelekileyo kwandisa uxinano lwangoku lwe-cyclohexanone oxidation kwaye kutshintsha i-RDS ye-COR ukusuka ekulungisweni kwakhona ukuya ekususweni kwe-hydrogenation equka i-Cα − H scission, ngelixa ukutsalwa okuphuculweyo kwe-cyclohexanone kucinezela i-OER. Uphuhliso lwe-MEA lufikelele kwimveliso ye-AA eqhubekayo kuxinano lwamandla ombane we-300 mA cm−2, ukusebenza kakuhle kwe-AA eyirekhodi ye-82%, kunye nemveliso ye-1536 μmol cm−2 h−1. Uvavanyo lweeyure ezingama-50 lubonise ukuba i-NiV-LDH-NS inozinzo oluhle njengoko inokugcina i-AA FE ephezulu kwi-MEA (> 80% iiyure ezingama-60 kwi-200 mA cm−2; > 70% iiyure ezingama-58 kwi-300 mA cm−2). Kufuneka kuqatshelwe ukuba kukho imfuneko yokuphuhlisa ii-AEM ezinamandla ngakumbi ukuze kufezekiswe uzinzo lwexesha elide kuxinano lwamandla ombane olufanelekileyo kwimizi-mveliso. Ukongeza, i-TEA igxininisa iingenelo zoqoqosho zezicwangciso zokusabela kwimveliso ye-AA kunye nokubaluleka kwee-catalysts ezisebenzayo eziphezulu kunye nobuchwepheshe bokuhlukanisa obuphambili ukunciphisa iindleko.