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Kupanga kwa electrosynthesis ya adipic acid (yomwe imachokera ku nayiloni 66) kuchokera ku mafuta a CA (osakaniza cyclohexanone ndi cyclohexanol) ndi njira yokhazikika yomwe ingalowe m'malo mwa njira zachikhalidwe zomwe zimafuna mikhalidwe yovuta. Komabe, kuchuluka kwa mphamvu yamagetsi kochepa komanso kusintha kwa mpweya wopikisana kumachepetsa kwambiri ntchito zake zamafakitale. Mu ntchitoyi, tikusintha nickel double hydroxide ndi vanadium kuti tiwonjezere kuchuluka kwa mphamvu yamagetsi ndikusunga mphamvu ya faradaic (>80%) pamlingo wokulirapo (1.5–1.9 V vs. hydrogen electrode yosinthika). Kafukufuku woyesera ndi wamalingaliro adavumbulutsa maudindo awiri ofunikira a kusintha kwa V, kuphatikiza kukonzanso mwachangu kwa catalyst ndikuwongolera bwino kwa cyclohexanone. Monga umboni wa lingaliro, tidapanga msonkhano wa membrane-electrode womwe udapanga adipic acid yokhala ndi mphamvu ya faradaic (82%) komanso kupanga (1536 μmol cm-2 h-1) pa kuchuluka kwa mphamvu yamagetsi koyenera mafakitale (300 mA cm-2), pomwe tikupeza kukhazikika >50 h. Ntchitoyi ikuwonetsa chothandizira chogwira ntchito bwino cha kupanga ma electrolyte a adipic acid okhala ndi zokolola zambiri komanso mphamvu zamafakitale.
Adipic acid (AA) ndi imodzi mwa ma aliphatic dicarboxylic acid ofunikira kwambiri ndipo imagwiritsidwa ntchito kwambiri popanga nayiloni 66 ndi ma polyamides ena kapena ma polima1. M'mafakitale, AA imapangidwa mwa kusakaniza cyclohexanol ndi cyclohexanone (monga mafuta a AA) pogwiritsa ntchito 50–60 vol% nitric acid ngati oxidizing agent. Njirayi ili ndi nkhawa zokhudzana ndi chilengedwe zokhudzana ndi kutulutsa kwa nitric acid ndi nitrogen oxides (N2O ndi NOx) ngati mpweya wowonjezera kutentha2,3. Ngakhale H2O2 ingagwiritsidwe ntchito ngati njira ina yowonjezerera oxidizing agent wobiriwira, mtengo wake wokwera komanso mikhalidwe yovuta yopangira zimapangitsa kuti zikhale zovuta kugwiritsa ntchito, ndipo njira yotsika mtengo komanso yokhazikika ikufunika4,5,6.
M'zaka khumi zapitazi, njira zopangira mankhwala ndi mafuta pogwiritsa ntchito electrocatalytic zakhala zikukopa chidwi chowonjezeka kuchokera kwa asayansi chifukwa cha ubwino wawo wogwiritsa ntchito mphamvu zongowonjezedwanso komanso kugwira ntchito pansi pa mikhalidwe yofatsa (monga kutentha kwa chipinda ndi kupanikizika kwa malo)7,8,9,10. Pachifukwa ichi, chitukuko cha kusintha kwa mafuta a KA kukhala AA ndi electrocatalytic ndikofunikira kwambiri kuti tipeze zabwino zomwe zili pamwambapa komanso kuchotsa kugwiritsa ntchito nitric acid ndi nitrous oxide emissions zomwe zimapezeka popanga zinthu wamba (Chithunzi 1a). Ntchito yoyambirira idachitidwa ndi Petrosyan et al., omwe adanena kuti electrocatalytic oxidation reaction ya cyclohexanone (COR; cyclohexanone kapena cyclohexanol yaphunziridwa kawirikawiri ngati ikuyimira mafuta a KA) pa nickel oxyhydroxide (NiOOH), koma kuchuluka kwa mphamvu yamagetsi (6 mA cm-2) ndi zokolola zapakati za AA (52%) zidapezeka11,12. Kuyambira pamenepo, kupita patsogolo kwakukulu kwachitika pakupanga ma catalyst opangidwa ndi nickel kuti awonjezere ntchito ya COR. Mwachitsanzo, chothandizira cha nickel hydroxide (Cu-Ni(OH)2) chopangidwa ndi mkuwa chinapangidwa kuti chilimbikitse kugawanika kwa Cα-Cβ mu cyclohexanol13. Posachedwapa tanena za chothandizira cha Ni(OH)2 chosinthidwa ndi sodium dodecyl sulfonate (SDS) kuti chipange malo ozungulira omwe amawonjezera cyclohexanone14.
a Mavuto a kupanga AA pogwiritsa ntchito electrooxidation ya mafuta a KA. b Kuyerekeza kwa COR ya electrocatalytic ya ma catalyst omwe adanenedwa kale ndi Ni-based ndi catalyst yathu mu dongosolo la ma electrode atatu ndi dongosolo la batri yoyenda11,13,14,16,26. Zambiri zokhudzana ndi magawo a reaction ndi magwiridwe antchito aperekedwa mu Matebulo Owonjezera 1 ndi 2. c Catalytic performance ya ma catalyst athu a NiV-LDH-NS a COR mu H-cell reactor ndi MEA, omwe amagwira ntchito pamlingo wosiyanasiyana.
Ngakhale njira zomwe zili pamwambapa zidawongolera ntchito ya COR, ma catalyst omwe afotokozedwa a Ni adawonetsa mphamvu yayikulu ya AA Faraday (FE) (>80%) yokha pa potentials zochepa, nthawi zambiri pansi pa 1.6 V poyerekeza ndi hydrogen electrode yosinthika (RHE, chidule cha VRHE). Chifukwa chake, kuchuluka kwa mphamvu yamagetsi komwe kunanenedwa (monga, kuchuluka kwa mphamvu yamagetsi kochulukitsidwa ndi FE) kwa AA nthawi zonse kumakhala pansi pa 60 mA cm−2 (Chithunzi 1b ndi Table Yowonjezera 1). Kuchuluka kwa mphamvu yamagetsi komwe kuli kotsika kwambiri kuposa zofunikira zamafakitale (>200 mA cm−2)15, zomwe zimalepheretsa kwambiri ukadaulo wamagetsi wamagetsi kuti apange AA yapamwamba (Chithunzi 1a; pamwamba). Kuti muwonjezere kuchuluka kwa mphamvu yamagetsi, mphamvu yabwino kwambiri (yamagetsi atatu) kapena mphamvu yayikulu yamagetsi (yamagetsi awiri) ingagwiritsidwe ntchito, yomwe ndi njira yosavuta yosinthira magetsi ambiri, makamaka mpweya wosinthika (OER). Komabe, pa COR pa mphamvu zambiri za anodic, OER ikhoza kukhala mpikisano waukulu pochepetsa FE ya AA, motero kuchepetsa kugwiritsa ntchito mphamvu moyenera (Chithunzi 1a; pansi). Mwachitsanzo, poyang'ana momwe zinthu zinalili kale (Chithunzi 1b ndi Table Supplementary 1), tinakhumudwa kupeza kuti FE ya AA pa SDS-modified Ni(OH)2 inachepa kuchoka pa 93% kufika pa 76% powonjezera mphamvu yogwiritsidwa ntchito kuchokera pa 1.5 VRHE kufika pa 1.7 VRHE14, pomwe FE ya AA pa CuxNi1-x(OH)2/CF inachepa kuchoka pa 93% kufika pa 69% powonjezera mphamvu kuchokera pa 1.52 VRHE kufika pa 1.62 VRHE16. Chifukwa chake, kuchuluka kwa AA komwe kunanenedwa sikukwera mofanana pa mphamvu zambiri, zomwe zimalepheretsa kwambiri kusintha kwa magwiridwe antchito a AA, osatchulanso kugwiritsa ntchito mphamvu zambiri chifukwa cha FE yotsika ya AA. Kuwonjezera pa ma catalyst okhala ndi nickel, ma catalyst okhala ndi cobalt awonetsanso ntchito yothandiza mu COR17,18,19. Komabe, kugwira ntchito kwawo kumachepa pamlingo wapamwamba, ndipo poyerekeza ndi ma catalyst okhala ndi Ni, ali ndi zolepheretsa zambiri pakugwiritsa ntchito mafakitale, monga kusinthasintha kwamitengo komanso zinthu zazing'ono zomwe zili m'nyumba. Chifukwa chake, ndikofunikira kupanga ma catalyst okhala ndi Ni okhala ndi mphamvu zambiri zamagetsi ndi FE mu COR kuti zikhale zothandiza kupeza zokolola zambiri za AA.
Mu ntchito iyi, tikunena za ma nanosheet awiri a hydroxide (NiV-LDH-NS) a vanadium(V)-modified nickel layered double hydroxide nanosheets (NiV-LDH-NS) ngati ma electrocatalysts ogwira ntchito bwino popanga AA kudzera mu COR, omwe amagwira ntchito pamlingo waukulu wokhala ndi OER yochepetsedwa kwambiri, kukwaniritsa kuchuluka kwa FE ndi current mu ma H-cell ndi ma membrane electrode assemblies (MEAs; Chithunzi 1 b). Choyamba tikuwonetsa kuti mphamvu ya acetylene oxidation efficiency pa chothandizira cha Ni(OH)2 nanosheet (Ni(OH)2-NS) chachizolowezi (Ni(OH)2-NS) imachepa, monga momwe timayembekezera, pamlingo wapamwamba, kuchokera pa 80% pa 1.5 VRHE mpaka 42% pa 1.9 VRHE. Mosiyana kwambiri, titasintha Ni(OH)2 ndi V, NiV-LDH-NS idawonetsa kuchuluka kwa current pamlingo wina ndipo, chofunika kwambiri, idasunga FE pamlingo waukulu. Mwachitsanzo, pa 1.9 VRHE, idawonetsa kuchuluka kwa mphamvu yamagetsi ya 170 mA cm−2 ndi FE ya 83%, yomwe ndi chothandizira chabwino kwambiri cha COR mu dongosolo la ma electrode atatu (Chithunzi 1c ndi Table Supplementary 1). Deta yoyesera ndi yongopeka ikuwonetsa kuti kusintha kwa V kumalimbikitsa kinetics yochepetsera kuchokera ku Ni(OH)2 kupita ku ma oxyhydroxides a Ni okhala ndi valent (Ni3+xOOH1-x), omwe amagwira ntchito ngati gawo logwira ntchito la COR. Kuphatikiza apo, kusintha kwa V kudakulitsa kuyamwa kwa cyclohexanone pamwamba pa catalyst, komwe kudasewera gawo lofunikira pakuletsa OER pa anodic potentials yayikulu. Kuti tiwonetse kuthekera kwa NiV-LDH-NS muzochitika zenizeni, tidapanga reactor ya MEA flow ndikuwonetsa FE ya AA (82%) pa kuchuluka kwa mphamvu yamagetsi kofunikira m'mafakitale (300 mA cm−2), komwe kuli kwakukulu kwambiri kuposa zotsatira zathu zam'mbuyomu mu reactor ya membrane flow (Chithunzi 1b ndi Table Supplementary 2). Kuchuluka kwa AA (1536 μmol cm−2 h−1) kunali kwakukulu kuposa komwe kunapezeka pogwiritsa ntchito njira yotenthetsera (<30 mmol gcatalyst−1 h−1)4. Kuphatikiza apo, chothandiziracho chinawonetsa kukhazikika bwino pogwiritsa ntchito MEA, kusunga FE >80% AA kwa maola 60 pa 200 mA cm−2 ndi FE >70% AA kwa maola 58 pa 300 mA cm−2. Pomaliza, kafukufuku woyambirira wotsimikizira (FEA) unawonetsa momwe njira zamagetsi zamagetsi zopangira AA zimagwirira ntchito.
Malinga ndi mabuku akale, Ni(OH)2 ndi chothandizira chomwe chimasonyeza ntchito yabwino ya COR, kotero Ni(OH)2-NS13,14 idapangidwa koyamba kudzera mu njira ya coprecipitation. Zitsanzozo zinawonetsa kapangidwe ka β-Ni(OH)2, komwe kunatsimikiziridwa ndi X-ray diffraction (XRD; Chithunzi 2a), ndipo ma nanosheets owonda kwambiri (makulidwe: 2–3 nm, kukula kwa lateral: 20–50 nm) adawonedwa pogwiritsa ntchito high-resolution transmission electron microscopy (HRTEM; Chithunzi Chowonjezera 1) ndi atomic force microscopy (AFM) muyeso (Chithunzi Chowonjezera 2). Kuphatikizika kwa ma nanosheets kudawonedwanso chifukwa cha mtundu wawo wowonda kwambiri.
Mawonekedwe a X-ray diffraction a Ni(OH)2-NS ndi NiV-LDH-NS. FE, throughput, ndi AA current density pa b Ni(OH)2-NS ndi c NiV-LDH-NS pa potentials zosiyanasiyana. Mipiringidzo yolakwika ikuyimira kupotoka kwa muyezo wa miyeso itatu yodziyimira payokha pogwiritsa ntchito catalyst yomweyo. d Chithunzi cha HRTEM cha NV-LDH-NS. Mipiringidzo yocheperako: 20 nm. Chithunzi cha HAADF-STEM cha NiV-LDH-NS ndi mapu ofanana oyambira omwe akuwonetsa kufalikira kwa Ni (wobiriwira), V (wachikasu), ndi O (buluu). Mipiringidzo yocheperako: 100 nm. f Ni 2p3/2, g O 1 s, ndi h V 2p3/2 XPS data ya Ni(OH)2-NS (pamwamba) ndi NiV-LDH-NS (pansi). i FE ndi j ndi machitidwe a AA pa ma catalyst awiri pa ma cycle 7. Mipiringidzo yolakwika ikuyimira kupotoka kwa muyezo wa miyeso itatu yodziyimira payokha pogwiritsa ntchito catalyst yomweyo ndipo ili mkati mwa 10%. Deta yosaphika ya a–c ndi f–j imaperekedwa m'mafayilo osaphika a data.
Kenako tinayesa momwe Ni(OH)2-NS imakhudzira COR. Pogwiritsa ntchito electrolysis yokhazikika, tinapeza 80% FE ya AA pa low potential (1.5 VRHE) popanda OER (Chithunzi 2b), zomwe zikusonyeza kuti COR ndi yabwino kwambiri kuposa OER pa low anodic potentials. Chopangidwa chachikulu chinapezeka kuti ndi glutaric acid (GA) yokhala ndi FE ya 3%. Kupezeka kwa kuchuluka kwa succinic acid (SA), malonic acid (MA), ndi oxalic acid (OA) kunayesedwanso ndi HPLC (onani Chithunzi Chowonjezera 3 cha kugawa kwa mankhwala). Palibe formic acid yomwe idapezeka mu mankhwalawa, zomwe zikusonyeza kuti carbonate ikhoza kupangidwa ngati C1 by-product. Kuti tiyese lingaliro ili, electrolyte kuchokera ku electrolysis yonse ya 0.4 M cyclohexanone idasinthidwa acid ndipo zinthu za gaseous zidadutsa mu yankho la Ca(OH)2. Zotsatira zake, yankholo linakhala lopanda madzi, kutsimikizira kupangidwa kwa carbonate pambuyo pa electrolysis. Komabe, chifukwa cha magetsi ochepa omwe amapangidwa panthawi ya electrolysis (Chithunzi 2b, c), kuchuluka kwa carbonate ndi kochepa ndipo n'kovuta kuwerengera. Kuphatikiza apo, zinthu zina za C2-C5 zitha kupangidwanso, koma kuchuluka kwake sikungathe kuwerengedwa. Ngakhale kuchuluka kwa zinthu zonse n'kovuta kuwerengera, 90% ya kuchuluka kwa electrochemical kukuwonetsa kuti njira zambiri zamagetsi zapezeka, zomwe zimapereka maziko omvetsetsa kwathu kwamakina. Chifukwa cha kuchuluka kochepa kwamagetsi (20 mA cm−2), phindu la AA linali 97 μmol cm−2 h−1 (Chithunzi 2b), lofanana ndi 19 mmol h−1 g−1 kutengera kuchuluka kwa catalyst (5 mg cm−2), komwe ndi kotsika kuposa mphamvu ya kutentha (~30 mmol h−1 g−1)1. Pamene mphamvu yogwiritsidwa ntchito inakwera kuchokera pa 1.5 mpaka 1.9 VRHE, ngakhale kuti kuchuluka kwa mphamvu yonse kunakwera (kuchokera pa 20 mpaka 114 mA cm−2), nthawi yomweyo panali kuchepa kwakukulu kwa AA FE, kuchokera pa 80% mpaka 42%. Kuchepa kwa FE pa mphamvu zabwino kwambiri kumachitika makamaka chifukwa cha mpikisano wa OER. Makamaka pa 1.7 VRHE, mpikisano wa OER umapangitsa kuti AA FE ichepe kwambiri, motero kuchepetsa pang'ono magwiridwe antchito a AA ndi kuchuluka kwa mphamvu yonse. Chifukwa chake, ngakhale kuchuluka kwa mphamvu pang'ono kwa AA kunakwera kuchokera pa 16 mpaka 48 mA cm−2 ndipo kupanga kwa AA kunakwera (kuchokera pa 97 mpaka 298 μmol cm−2 h−1), mphamvu yowonjezera yambiri idagwiritsidwa ntchito (2.5 W h gAA−1 yowonjezera kuchokera pa 1.5 mpaka 1.9 VRHE), zomwe zinapangitsa kuti mpweya wa kaboni utuluke 2.7 g CO2 gAA−1 (tsatanetsatane wa kuwerengera waperekedwa mu Supplementary Note 1). OER yomwe yatchulidwa kale ngati mpikisano wa COR reaction pa anodic potentials yayikulu ikugwirizana ndi malipoti am'mbuyomu ndipo ikuyimira vuto lalikulu pakukweza kupanga kwa AA14,17.
Kuti tipange chothandizira cha Ni(OH)2-NS chogwira ntchito bwino kwambiri cha COR, choyamba tidasanthula gawo logwira ntchito. Tinawona nsonga pa 473 cm-1 ndi 553 cm-1 mu zotsatira zathu za in situ Raman spectroscopy (Chithunzi Chowonjezera 4), chogwirizana ndi kupindika ndi kutambasula kwa ma bond a Ni3+-O mu NiOOH, motsatana. Zalembedwa kuti NiOOH ndi zotsatira za kuchepetsa kwa Ni(OH)2 ndi kusonkhanitsa kwa Ni(OH)O pa anodic potentials, ndipo kwenikweni ndi gawo logwira ntchito mu electrocatalytic oxidation20,21. Chifukwa chake, tikuyembekeza kuti kufulumizitsa njira yokonzanso gawo la Ni(OH)2 kupita ku NiOOH kungapangitse ntchito yothandiza ya COR.
Tinayesa kusintha Ni(OH)2 ndi zitsulo zosiyanasiyana popeza zidawonedwa kuti kusintha kwa heteroatom kumalimbikitsa kukonzanso gawo mu transition metal oxides/hydroxides22,23,24. Zitsanzozo zinapangidwa pogwiritsa ntchito co-deposition ya Ni ndi precursor yachiwiri yachitsulo. Pakati pa zitsanzo zosiyanasiyana zosinthidwa ndi zitsulo, chitsanzo cha V-modified (V:Ni atomic ratio 1:8) (chotchedwa NiV-LDH-NS) chinawonetsa kuchuluka kwa mphamvu yamagetsi mu COR (Chithunzi Chowonjezera 5) ndipo chofunika kwambiri, AA FE yapamwamba pawindo lalikulu la mphamvu. Makamaka, pa mphamvu yamagetsi yochepa (1.5 VRHE), kuchuluka kwa mphamvu yamagetsi ya NiV-LDH-NS kunali kokwera nthawi 1.9 kuposa kwa Ni(OH)2-NS (39 vs. 20 mA cm−2), ndipo AA FE inali yofanana pa ma catalyst onse awiri (83% vs. 80%). Chifukwa cha kuchuluka kwa mphamvu zamagetsi ndi FE AA yofanana, kupanga kwa NiV-LDH-NS ndikokwera nthawi 2.1 kuposa kwa Ni(OH)2-NS (204 vs. 97 μmol cm−2 h−1), kusonyeza zotsatira zolimbikitsa za kusintha kwa V pa mphamvu zamagetsi zamagetsi pa mphamvu zochepa (Chithunzi 2c).
Ndi mphamvu yogwiritsidwa ntchito ikuwonjezeka (monga 1.9 VRHE), kuchuluka kwa mphamvu pa NiV-LDH-NS kuli kokwera nthawi 1.5 kuposa kwa Ni(OH)2-NS (170 vs. 114 mA cm−2), ndipo kuwonjezekako kuli kofanana ndi kwa mphamvu zotsika (nthawi 1.9 kuposa). Chodziwika bwino n'chakuti, NiV-LDH-NS idasunga AA FE yapamwamba (83%) ndipo OER idachepetsedwa kwambiri (O2 FE 4%; Chithunzi 2c), ikuposa Ni(OH)2-NS yogwira ntchito komanso ma catalyst omwe adanenedwa kale omwe ali ndi AA FE yotsika kwambiri pa mphamvu zotsika kwambiri (Table Supplementary 1). Chifukwa cha kuchuluka kwa FE kwa AA muwindo lalikulu (1.5–1.9 VRHE), kuchuluka kwa AA komwe kunachitika pa 867 μmol cm−2 h−1 (kofanana ndi 174.3 mmol g−1 h−1) kunapezeka pa 1.9 VRHE, zomwe zinawonetsa magwiridwe antchito abwino mu machitidwe a electrocatalytic komanso thermocatalytic pamene ntchitoyo inakhazikika ndi kuchuluka kwa ma samples a NiV-LDH-NS (Chithunzi Chowonjezera 6).
Kuti timvetse kuchuluka kwa mphamvu zamagetsi ndi FE yapamwamba pamlingo waukulu pambuyo posintha Ni(OH)2 ndi V, tinafotokoza kapangidwe ka NiV-LDH-NS. Zotsatira za XRD zinasonyeza kuti kusintha ndi V kunayambitsa kusintha kwa gawo kuchokera ku β-Ni(OH)2 kupita ku α-Ni(OH)2, ndipo palibe mitundu yokhudzana ndi V yomwe inapezeka (Chithunzi 2a). Zotsatira za HRTEM zikusonyeza kuti NiV-LDH-NS imalandira mawonekedwe a ma nanosheets a Ni(OH)2-NS owonda kwambiri ndipo ali ndi miyeso yofanana ya mbali (Chithunzi 2d). Kuyeza kwa AFM kunawonetsa chizolowezi champhamvu cha ma nanosheets, zomwe zimapangitsa kuti makulidwe oyezeka akhale pafupifupi 7 nm (Chithunzi Chowonjezera 7), chomwe ndi chachikulu kuposa cha Ni(OH)2-NS (makulidwe: 2–3 nm). Kusanthula kwa ma X-ray spectroscopy (EDS) mapping (Chithunzi 2e) kunasonyeza kuti zinthu za V ndi Ni zinali zogawidwa bwino mu ma nanosheets. Kuti timvetse bwino kapangidwe ka magetsi ka V ndi momwe imakhudzira Ni, tinagwiritsa ntchito X-ray photoelectron spectroscopy (XPS) (Chithunzi 2f–h). Ni(OH)2-NS inawonetsa mapiri a spin-orbit a Ni2+ (phiri lachikazi pa 855.6 eV, phiri la satellite pa 861.1 eV, Chithunzi 2f)25. O1 s XPS spectrum ya Ni(OH)2-NS ikhoza kugawidwa m'magulu atatu, omwe mapiri a 529.9, 530.9 ndi 532.8 eV amagwirizanitsidwa ndi lattice oxygen (OL), hydroxyl group (Ni-OH) ndi oxygen absorbed on surface defects (OAds), motsatana (Chithunzi 2g)26,27,28,29. Pambuyo pa kusintha kwa V, nsonga ya V 2p3/2 inaonekera, yomwe imatha kugawidwa m'magawo atatu omwe ali pa 517.1 eV (V5+), 516.6 eV (V4+) ndi 515.8 eV (V3+), motsatana, kusonyeza kuti mitundu ya V m'kapangidwe kake imapezeka makamaka m'malo okhala ndi okosijeni wambiri (Chithunzi 2h) 25,30,31. Kuphatikiza apo, nsonga ya Ni 2p pa 855.4 eV mu NiV-LDH-NS inasinthidwa molakwika (ndi pafupifupi 0.2 eV) poyerekeza ndi yomwe ili mu Ni(OH)2-NS, kusonyeza kuti ma elekitironi anasamutsidwa kuchokera ku V kupita ku Ni. Mkhalidwe wotsika wa valence wa Ni womwe unawonedwa pambuyo pa kusintha kwa V unali wogwirizana ndi zotsatira za Ni K-edge X-ray absorption near-edge spectroscopy (XANES) (onani gawo la "V Modification Promotes Catalyst Reduction" pansipa kuti mudziwe zambiri). NiV-LDH-NS pambuyo pa chithandizo cha COR kwa ola limodzi idatchulidwa kuti NiV-LDH-POST ndipo idadziwika bwino pogwiritsa ntchito ma microscopy a ma electron otumizira, mapping a EDS, X-ray diffraction, Raman spectroscopy, ndi muyeso wa XPS (Zithunzi Zowonjezera 8 ndi 9). Ma catalyst adatsalira ngati ma aggregates okhala ndi mawonekedwe a nanosheet owonda kwambiri (Zithunzi Zowonjezera 8a–c). Kuchuluka kwa zitsanzo kunachepa ndipo kuchuluka kwa V kunachepa chifukwa cha V leaching ndi catalyst reconstruction (Zithunzi Zowonjezera 8d–f). Ma XPS spectra adawonetsa kuchepa kwa V peak intensity (Zithunzi Zowonjezera 9), zomwe zidachitika chifukwa cha V leaching. Kuphatikiza apo, kusanthula kwa O1s spectrum (Chithunzi Chowonjezera 9d) ndi muyeso wa electron paramagnetic resonance (EPR) (Chithunzi Chowonjezera 10) kunawonetsa kuti kuchuluka kwa mpweya woipa pa NiV-LDH-NS kunawonjezeka pambuyo pa ola limodzi la electrolysis, zomwe zingayambitse kusintha koyipa kwa mphamvu yomangira Ni 2p (onani Zithunzi Zowonjezera 9 ndi 10 kuti mudziwe zambiri)26,27,32,33. Chifukwa chake, NiV-LDH-NS sinasinthe kwambiri kapangidwe kake pambuyo pa ola limodzi la COR.
Kuti titsimikizire udindo wofunika wa V pakukweza COR, tinapanga ma catalyst a NiV-LDH okhala ndi ma atomu a V:Ni osiyanasiyana (1:32, 1:16, ndi 1:4, omwe amatchedwa NiV-32, NiV-16, ndi NiV-4, motsatana) kupatula 1:8 pogwiritsa ntchito njira yomweyo yolumikizirana. Zotsatira za mapu a EDS zikuwonetsa kuti chiŵerengero cha atomu cha V:Ni mu catalyst chili pafupi ndi cha precursor (Chithunzi Chowonjezera 11a–e). Ndi kuwonjezeka kwa kusintha kwa V, mphamvu ya V 2p spectrum imawonjezeka, ndipo mphamvu yomangira ya dera la Ni 2p imasinthasintha mosalekeza kupita ku mbali yoyipa (Chithunzi Chowonjezera 12). Nthawi yomweyo, gawo la OL linawonjezeka pang'onopang'ono. Zotsatira za mayeso a catalytic zikusonyeza kuti OER ikhoza kuchepetsedwa bwino ngakhale mutasintha pang'ono V (chiŵerengero cha atomiki cha V:Ni cha 1:32), pomwe O2 FE ikutsika kuchokera pa 27% mpaka 11% pa 1.8 VRHE mutasintha V (Chithunzi Chowonjezera 11f). Ndi kuwonjezeka kwa chiŵerengero cha V:Ni kuchokera pa 1:32 mpaka 1:8, ntchito ya catalytic inakula. Komabe, ndi kuwonjezeka kwina kwa kusintha kwa V (chiŵerengero cha V:Ni cha 1:4), kuchuluka kwa mphamvu yamagetsi kumachepa, komwe timaganiza kuti kumachitika chifukwa cha kuchepa kwa kuchuluka kwa malo omwe amagwira ntchito a Ni (makamaka gawo logwira ntchito la NiOOH; Chithunzi Chowonjezera 11f). Chifukwa cha zotsatira zolimbikitsa za kusintha kwa V ndi kusunga malo omwe amagwira ntchito a Ni, catalyst yokhala ndi chiŵerengero cha V:Ni cha 1:8 inawonetsa magwiridwe antchito apamwamba kwambiri a FE ndi AA mu mayeso owunikira chiŵerengero cha V:Ni. Pofuna kufotokoza bwino ngati chiŵerengero cha V:Ni chikukhalabe chokhazikika pambuyo pa electrolysis, kapangidwe ka ma catalyst omwe adagwiritsidwa ntchito kanadziwika. Zotsatira zake zikusonyeza kuti pa ma catalyst omwe ali ndi ma V:Ni ratios oyamba kuyambira 1:16 mpaka 1:4, chiŵerengero cha V:Ni chinachepa kufika pa 1:22 pambuyo pa reaction, zomwe zitha kukhala chifukwa cha leaching ya V chifukwa cha catalyst reconstruction (Chithunzi Chowonjezera 13). Dziwani kuti ma AA FE ofanana adawonedwa pamene chiŵerengero choyamba cha V:Ni chinali chofanana kapena chapamwamba kuposa 1:16 (Chithunzi Chowonjezera 11f), chomwe chingafotokozedwe ndi catalyst reconstruction yomwe imabweretsa ma V:Ni ratios ofanana mu ma catalyst omwe akuwonetsa magwiridwe antchito ofanana.
Kuti titsimikizire kufunika kwa V-modified Ni(OH)2 pakukweza magwiridwe antchito a COR, tinapanga njira zina ziwiri zopangira kuti tilowetse V mu zinthu za Ni(OH)2-NS. Imodzi ndi njira yosakanizira, ndipo chitsanzocho chimatchedwa NiV-MIX; china ndi njira yotsatizana yothira madzi, ndipo chitsanzocho chimatchedwa NiV-SP. Tsatanetsatane wa kapangidwe kake waperekedwa mu gawo la Njira. Mapu a SEM-EDS adawonetsa kuti V idasinthidwa bwino pamwamba pa Ni(OH)2-NS ya zitsanzo zonse ziwiri (Chithunzi Chowonjezera 14). Zotsatira za electrolysis zikuwonetsa kuti pa 1.8 VRHE, mphamvu ya AA pa ma electrode a NiV-MIX ndi NiV-SP ndi 78% ndi 79%, motsatana, zonse zikuwonetsa mphamvu yapamwamba kuposa Ni(OH)2-NS (51%). Kuphatikiza apo, OER pa ma electrode a NiV-MIX ndi NiV-SP idachepetsedwa (FE O2: 7% ndi 2%, motsatana) poyerekeza ndi Ni(OH)2-NS (FE O2: 27%). Zotsatirazi zikutsimikizira zotsatira zabwino za kusintha kwa V mu Ni(OH)2 pa kuletsa kwa OER (Chithunzi Chowonjezera 14). Komabe, kukhazikika kwa ma catalyst kunasokonekera, zomwe zinawonetsedwa ndi kuchepa kwa FE AA pa NiV-MIX kufika pa 45% ndi pa NiV-SP kufika pa 35% pambuyo pa ma COR cycles asanu ndi awiri, zomwe zikutanthauza kufunika kogwiritsa ntchito njira zoyenera zokhazikitsira mitundu ya V, monga kusintha kwa V mu lattice ya Ni(OH)2 mu NiV-LDH-NS, yomwe ndi chothandizira chachikulu pantchitoyi.
Tinayesanso kukhazikika kwa Ni(OH)2-NS ndi NiV-LDH-NS mwa kuyika COR m'ma cycle angapo. Kuchitapo kanthu kunachitika kwa ola limodzi pa cycle ndipo electrolyte inasinthidwa pambuyo pa cycle iliyonse. Pambuyo pa cycle ya 7, magwiridwe antchito a FE ndi AA pa Ni(OH)2-NS adatsika ndi 50% ndi 60%, motsatana, pomwe kuwonjezeka kwa OER kudawonedwa (Chithunzi 2i, j). Pambuyo pa cycle iliyonse, tidasanthula ma curve a cyclic voltammetry (CV) a ma catalyst ndipo tidawona kuti peak ya okosijeni ya Ni2+ idatsika pang'onopang'ono, zomwe zikusonyeza kuchepa kwa mphamvu ya redox ya Ni (Chithunzi Chowonjezera 15a-c). Pamodzi ndi kuwonjezeka kwa kuchuluka kwa Nication mu electrolyte panthawi ya electrolysis (Chithunzi Chowonjezera 15d), tidanena kuti kuchepa kwa magwiridwe antchito (kuchepa kwa FE ndi AA productivity) kudachitika chifukwa cha leaching ya Ni kuchokera ku catalyst, zomwe zimapangitsa kuti substrate yokhala ndi thovu ya Ni iwonetse ntchito ya OER. Mosiyana ndi zimenezi, NiV-LDH-NS inachepetsa kuchepa kwa kupanga kwa FE ndi AA kufika pa 10% (Chithunzi 2i, j), zomwe zikusonyeza kuti kusintha kwa V kunaletsa bwino kutuluka kwa Ni (Chithunzi Chowonjezera 15d). Kuti timvetse kukhazikika kwa kusintha kwa V, tinachita mawerengedwe a chiphunzitso. Malinga ndi mabuku am'mbuyomu34,35, kusintha kwa enthalpy kwa njira yochotsera metallization ya maatomu achitsulo pamwamba pa chothandizira kungagwiritsidwe ntchito ngati kufotokozera koyenera kuti tiwunikire kukhazikika kwa chothandizira. Chifukwa chake, kusintha kwa enthalpy kwa njira yochotsera metallization ya maatomu a Ni pamwamba pa (100) pa Ni(OH)2-NS yomangidwanso ndi NiV-LDH-NS (NiOOH ndi NiVOOH, motsatana) kunayesedwa (tsatanetsatane wa kapangidwe ka chitsanzocho wafotokozedwa mu Supplementary Note 2 ndi Supplementary Fig. 16). Njira yochotsera metallization ya Ni kuchokera ku NiOOH ndi NiVOOH inawonetsedwa (Chithunzi Chowonjezera 17). Mtengo wa mphamvu wa Ni demetallization pa NiVOOH (0.0325 eV) ndi wokwera kuposa wa NiOOH (0.0005 eV), zomwe zikusonyeza kuti kusintha kwa V kumawonjezera kukhazikika kwa NiOOH.
Pofuna kutsimikizira zotsatira za OER zoletsa NiV-LDH-NS, makamaka pa ma anodic potentials ambiri, differential electrochemical mass spectrometry (DEMS) idachitidwa kuti ifufuze kapangidwe ka O2 komwe kamadalira mphamvu pa zitsanzo zosiyanasiyana. Zotsatira zake zidawonetsa kuti popanda cyclohexanone, O2 pa NiV-LDH-NS idawonekera pa mphamvu yoyamba ya 1.53 VRHE, yomwe inali yotsika pang'ono kuposa ya O2 pa Ni(OH)2-NS (1.62 VRHE) (Chithunzi Chowonjezera 18). Zotsatirazi zikusonyeza kuti kuletsa kwa OER kwa NiV-LDH-NS panthawi ya COR sikungakhale chifukwa cha ntchito yake yotsika ya OER, yomwe imagwirizana ndi kuchuluka kwamphamvu kwamagetsi mu ma curve a linear sweep voltammetry (LSV) pa NiV-LDH-NS kuposa pa Ni(OH)2-NS yopanda cyclohexanone (Chithunzi Chowonjezera 19). Pambuyo poyambitsa cyclohexanone, kusintha kwa O2 komwe kwachedwa (mwina chifukwa cha ubwino wa thermodynamic wa COR) kumafotokoza za FE yapamwamba ya AA m'dera lotsika kwambiri. Chofunika kwambiri, mphamvu yoyambira ya OER pa NiV-LDH-NS (1.73 VRHE) imachedwa kwambiri kuposa ya Ni(OH)2-NS (1.65 VRHE), zomwe zikugwirizana ndi FE yapamwamba ya AA ndi FE yochepa ya O2 pa NiV-LDH-NS pamphamvu zabwino kwambiri (Chithunzi 2c).
Kuti timvetse bwino momwe kusintha kwa V kumathandizira, tinasanthula momwe OER ndi COR reaction kinetics zimagwirira ntchito pa Ni(OH)2-NS ndi NiV-LDH-NS poyesa malo awo otsetsereka a Tafel. Ndikofunikira kudziwa kuti kuchuluka kwa magetsi komwe kulipo m'dera la Tafel kumachitika chifukwa cha okosijeni wa Ni2+ kupita ku Ni3+ panthawi yoyeserera ya LSV kuchokera ku mphamvu yotsika kupita ku mphamvu yokwera. Kuti tichepetse mphamvu ya okosijeni wa Ni2+ pa muyeso wa malo otsetsereka a COR Tafel, choyamba tinayika okosijeni pa 1.8 VRHE kwa mphindi 10 kenako tinachita mayeso a LSV mu reverse scan mode, mwachitsanzo, kuchokera ku mphamvu yokwera kupita ku mphamvu yotsika (Chithunzi Chowonjezera 20). Mzere woyambirira wa LSV unakonzedwa ndi 100% iR compensation kuti tipeze malo otsetsereka a Tafel. Popanda cyclohexanone, malo otsetsereka a Tafel a NiV-LDH-NS (41.6 mV dec−1) anali otsika kuposa a Ni(OH)2-NS (65.5 mV dec−1), zomwe zikusonyeza kuti kinetics ya OER ikhoza kukulitsidwa ndi kusintha kwa V (Chithunzi Chowonjezera 20c). Pambuyo poyambitsa cyclohexanone, malo otsetsereka a Tafel a NiV-LDH-NS (37.3 mV dec−1) anali otsika kuposa a Ni(OH)2-NS (127.4 mV dec−1), zomwe zikusonyeza kuti kusintha kwa V kunali ndi mphamvu yodziwikiratu ya kinetic pa COR poyerekeza ndi OER (Chithunzi Chowonjezera 20d). Zotsatirazi zikusonyeza kuti ngakhale kusintha kwa V kumalimbikitsa OER pamlingo wina, kumathandizira kwambiri kinetics ya COR, zomwe zimapangitsa kuti FE ya AA iwonjezereke.
Kuti timvetse momwe kusintha kwa V komwe kwatchulidwa pamwambapa kumakhudzira magwiridwe antchito a FE ndi AA, tinayang'ana kwambiri pa kafukufuku wa makina. Malipoti ena am'mbuyomu awonetsa kuti kusintha kwa heteroatom kumatha kuchepetsa kupangika kwa ma catalyst ndikuwonjezera malo ogwirira ntchito zamagetsi (EAS), motero kuonjezera kuchuluka kwa malo ogwira ntchito ndikukweza ntchito yothandiza36,37. Kuti tifufuze kuthekera kumeneku, tinachita muyeso wa ECSA isanayambe komanso itatha kuyambitsa magetsi, ndipo zotsatira zake zinawonetsa kuti ECSA ya Ni(OH)2-NS ndi NiV-LDH-NS inali yofanana (Chithunzi Chowonjezera 21), kupatula mphamvu ya kuchuluka kwa malo ogwira ntchito pambuyo pa kusintha kwa V pakukula kwa mphamvu yothandiza.
Malinga ndi chidziwitso chovomerezeka, mu Ni(OH)2-catalyzed electrooxidation ya alcohols kapena ma substrates ena a nucleophilic, Ni(OH)2 poyamba imataya ma elekitironi ndi ma protoni kenako imachepetsedwa kukhala NiOOH kudzera mu masitepe a electrochemical pa anodic potential38,39,40,41. NiOOH yopangidwayo imagwira ntchito ngati mtundu weniweni wa COR womwe umagwira ntchito kuti uchotse hydrogen ndi ma elekitironi kuchokera ku nucleophilic substrate kudzera mu masitepe a mankhwala kuti upange oxidized product20,41. Komabe, posachedwapa zanenedwa kuti ngakhale kuchepetsa kwa NiOOH kungakhale ngati sitepe yodziwira liwiro (RDS) ya electrooxidation ya mowa pa Ni(OH)2, monga momwe zanenedwera m'mabuku aposachedwa, oxidation ya Ni3+ alcohols ikhoza kukhala njira yodzidzimutsa kudzera mu non-redox electron transfer kudzera mu ma orbitals osagwira ntchito a Ni3+41,42. Motsogozedwa ndi kafukufuku wamakina omwe adanenedwa m'mabuku omwewo, tidagwiritsa ntchito dimethylglyoxime disodium salt octahydrate (C4H6N2Na2O2 8H2O) ngati molekyulu yofufuzira kuti igwire mapangidwe aliwonse a Ni2+ omwe amachokera ku kuchepa kwa Ni3+ panthawi ya COR (Chithunzi Chowonjezera 22 ndi Chidziwitso Chowonjezera 3). Zotsatira zake zidawonetsa kupangika kwa Ni2+, kutsimikizira kuti kuchepa kwa mankhwala a NiOOH ndi electrooxidation ya Ni(OH)2 zidachitika nthawi imodzi panthawi ya COR. Chifukwa chake, ntchito yothandiza ikhoza kudalira kwambiri kinetics ya kuchepa kwa Ni(OH)2 kukhala NiOOH. Kutengera mfundo iyi, tidafufuzanso ngati kusintha kwa V kungafulumizitse kuchepa kwa Ni(OH)2 ndikupangitsa COR kukhala yabwino.
Choyamba tidagwiritsa ntchito njira za Raman zomwe zili mu situ kuti tisonyeze kuti NiOOH ndiye gawo logwira ntchito la COR pa Ni(OH)2-NS ndi NiV-LDH-NS powona kupangika kwa NiOOH pa mphamvu zabwino ndi kugwiritsidwa ntchito kwake pambuyo poyambitsa cyclohexanone, kutsatira njira ya "electrochemical-chemical" yomwe yatchulidwa pamwambapa (Chithunzi 3a). Kuphatikiza apo, reactivity ya NiV-LDH-NS yomangidwanso idaposa ya Ni(OH)2-NS, monga momwe zasonyezedwera ndi kutha msanga kwa chizindikiro cha Ni3+–O Raman. Kenako tidawonetsa kuti NiV-LDH-NS idawonetsa mphamvu zochepa zopangira NiOOH poyerekeza ndi Ni(OH)2-NS pakakhala kapena kusakhalapo kwa cyclohexanone (Chithunzi 3b, c ndi Chithunzi Chowonjezera 4c, d). Chochititsa chidwi n'chakuti, mphamvu ya OER ya NiV-LDH-NS imapangitsa kuti thovu zambiri ziume pa lenzi yakutsogolo ya cholinga choyezera cha Raman, zomwe zimapangitsa kuti nsonga ya Raman pa 1.55 VRHE izimiririke (Chithunzi Chowonjezera 4d). Malinga ndi zotsatira za DEMS (Chithunzi Chowonjezera 18), kuchuluka kwa mphamvu zomwe zilipo pa mphamvu zochepa (VRHE < 1.58 ya Ni(OH)2-NS ndi VRHE < 1.53 ya NiV-LDH-NS) makamaka kumachitika chifukwa cha kumangidwanso kwa ma ioni a Ni2+ m'malo mwa OER popanda cyclohexanone. Chifukwa chake, nsonga ya okosijeni ya Ni2+ mu LSV curve ndi yamphamvu kuposa ya NiV-LDH-NS, zomwe zikusonyeza kuti kusintha kwa V kumapatsa NiV-LDH-NS mphamvu yowonjezera yokonzanso (onani Chithunzi Chowonjezera 19 kuti mudziwe zambiri).
a Ma spectra a Raman omwe ali mu situ a Ni(OH)2-NS (kumanzere) ndi NiV-LDH-NS (kumanja) pansi pa mikhalidwe ya OCP pambuyo pa preoxidation pa 1.5 VRHE mu 0.5 M KOH ndi 0.4 M cyclohexanone kwa masekondi 60. b Ma spectra a Raman omwe ali mu situ a Ni(OH)2-NS ndi c NiV-LDH-NS mu 0.5 M KOH + 0.4 M cyclohexanone pa potentials zosiyanasiyana. d Ma spectra a XANES omwe ali mu situ a Ni(OH)2-NS ndi NiV-LDH-NS pa Ni K-edge mu 0.5 M KOH ndi e 0.5 M KOH ndi 0.4 M cyclohexanone. Chithunzichi chikuwonetsa dera la ma spectral lomwe lakulitsidwa pakati pa 8342 ndi 8446 eV. f Ma Valence states a Ni mu Ni(OH)2-NS ndi NiV-LDH-NS pa potentials zosiyanasiyana. g In situ Ni EXAFS spectra ya NiV-LDH-NS isanayambe komanso itatha kuikidwa kwa cyclohexanone pamlingo wosiyanasiyana. h Zitsanzo za chiphunzitso cha Ni(OH)2-NS ndi NiV-LDH-NS. Pamwamba: Pa Ni(OH)2-NS, kusintha pang'onopang'ono kuchokera ku Ni(OH)2-NS kupita ku NiOOH kumagwira ntchito ngati RDS, pomwe cyclohexanone imachepetsa mtundu wa Ni-valent wapamwamba kudzera mu njira zamakemikolo kuti isunge mkhalidwe wa Ni-valent wotsika kuti ipange AA. Pansi: Pa NiV-LDH-NS, gawo lokonzanso limathandizidwa ndi kusintha kwa V, zomwe zimapangitsa kuti RDS isamutsidwe kuchokera ku gawo lokonzanso kupita ku gawo la mankhwala. i Kusintha kwa mphamvu ya Gibbs pakusintha kwa Ni(OH)2-NS ndi NiV-LDH-NS. Deta yaiwisi ya aj ndi i imaperekedwa mu fayilo ya data yaiwisi.
Kuti tifufuze kusintha kwa kapangidwe ka atomu ndi zamagetsi panthawi yochepetsa mphamvu ya catalyst, tinachita mayeso a in situ X-ray absorption spectroscopy (XAS), omwe adapereka chida champhamvu chofufuzira mphamvu za mitundu ya Ni m'magawo atatu otsatizana: OER, injection ya cyclohexanone, ndi COR at open circuit potential (OCP). Chithunzichi chikuwonetsa ma K-edge XANES spectra a Ni okhala ndi mphamvu yowonjezera isanafike komanso itatha injection ya cyclohexanone (Chithunzi 3d, e). Pa mphamvu yomweyo, mphamvu ya absorption edge ya NiV-LDH-NS ndi yabwino kwambiri kuposa ya Ni(OH)2-NS (Chithunzi 3d, e, inset). Valence yapakati ya Ni pansi pa chikhalidwe chilichonse idayesedwa ndi linear combined fit ya ma XANES spectra ndi regression ya Ni K-edge absorption energy shift (Chithunzi 3f), ndi reference spectrum yotengedwa kuchokera m'mabuku ofalitsidwa (Chithunzi Chowonjezera 23)43.
Mu gawo loyamba (musanayambe kugwiritsa ntchito cyclohexanone, yogwirizana ndi njira ya OER; Chithunzi 3f, kumanzere), pa mphamvu ya chothandizira chosamangidwanso (<1.3 VRHE), mkhalidwe wa valence wa Ni mu NiV-LDH-NS (+1.83) ndi wocheperako pang'ono kuposa wa Ni(OH)2-NS (+1.97), womwe ungatchulidwe ndi kusamutsa kwa ma elekitironi kuchokera ku V kupita ku Ni, mogwirizana ndi zotsatira za XPS zomwe zatchulidwa pamwambapa (Chithunzi 2f). Pamene mphamvuyo yapitirira mfundo yochepetsera (1.5 VRHE), mkhalidwe wa valence wa Ni mu NiV-LDH-NS (+3.28) umasonyeza kuwonjezeka koonekeratu poyerekeza ndi kwa Ni(OH)2-NS (+2.49). Pa mphamvu yapamwamba (1.8 VRHE), mkhalidwe wa valence wa tinthu ta Ni tomwe timapezeka pa NiV-LDH-NS (+3.64) ndi wokwera kuposa wa Ni(OH)2-NS (+3.47). Malinga ndi malipoti aposachedwa, njira imeneyi ikugwirizana ndi kupangidwa kwa mitundu ya Ni4+ yokhala ndi valent yapamwamba m'mapangidwe a Ni3+xOOH1-x (Ni3+x ndi mitundu yosakanikirana ya Ni3+ ndi Ni4+), yomwe yawonetsa kale ntchito yowonjezera ya catalytic mu dehydrogenation ya mowa38,39,44. Chifukwa chake, magwiridwe antchito apamwamba a NiV-LDH-NS mu COR akhoza kukhala chifukwa cha kuchepetsedwa kwamphamvu kuti apange mitundu ya Ni yokhala ndi valent yapamwamba.
Mu gawo lachiwiri (kuyambitsa cyclohexanone pambuyo potsegula mphete, Chithunzi 3f), mkhalidwe wa valence wa Ni pa ma catalyst onse awiri unachepa kwambiri, zomwe zikugwirizana ndi njira yochepetsera ya Ni3+xOOH1-x ndi cyclohexanone, zomwe zikugwirizana ndi zotsatira za in situ Raman spectroscopy (Chithunzi 3a), ndipo mkhalidwe wa valence wa Ni unatsala pang'ono kubwerera ku mkhalidwe woyambirira (gawo loyamba pa mphamvu yotsika), kusonyeza kusinthika kwa njira ya redox ya Ni3+xOOH1-x.
Mu gawo lachitatu (njira ya COR) pa COR potentials (1.5 ndi 1.8 VRHE; Chithunzi 3f, kumanja), mkhalidwe wa valence wa Ni mu Ni(OH)2-NS unakwera pang'ono (+2.16 ndi +2.40), womwe ndi wotsika kwambiri kuposa mphamvu yomweyo mu gawo loyamba (+2.49 ndi +3.47). Zotsatirazi zikusonyeza kuti pambuyo pa jakisoni wa cyclohexanone, COR imachepetsedwa ndi kinetically ndi oxidation pang'onopang'ono ya Ni2+ kupita ku Ni3+x (mwachitsanzo, kukonzanso kwa Ni) m'malo mwa sitepe ya mankhwala pakati pa NiOOH ndi cyclohexanone pa Ni(OH)2-NS, zomwe zimasiya Ni mu mkhalidwe wotsika wa valence. Chifukwa chake, tikuganiza kuti kukonzanso kwa Ni kumatha kugwira ntchito ngati RDS mu njira ya COR pa Ni(OH)2-NS. Mosiyana ndi zimenezi, NiV-LDH-NS inasunga valence yayikulu ya mitundu ya Ni (>3) panthawi ya COR, ndipo valence inachepa pang'ono (zosakwana 0.2) poyerekeza ndi sitepe yoyamba pa mphamvu yomweyo (1.65 ndi 1.8 VRHE), zomwe zikusonyeza kuti kusintha kwa V kunalimbikitsa okosijeni wa Ni2+ kukhala Ni3+x, zomwe zinapangitsa kuti njira yochepetsera Ni ikhale yofulumira kuposa sitepe ya mankhwala yochepetsera cyclohexanone. Zotsatira za Extended X-ray absorption fine structure (EXAFS) zinawonetsanso kusintha kwathunthu kwa ma bond a Ni–O (kuchokera pa 1.6 mpaka 1.4 Å) ndi Ni–Ni(V) (kuchokera pa 2.8 mpaka 2.4 Å) pamaso pa cyclohexanone. Izi zikugwirizana ndi kumangidwanso kwa gawo la Ni(OH)2 kupita ku gawo la NiOOH ndi kuchepetsa kwa mankhwala kwa gawo la NiOOH ndi cyclohexanone (Chithunzi 3g). Komabe, cyclohexanone inalepheretsa kwambiri kuchepa kwa Ni(OH)2-NS (onani Supplementary Note 4 ndi Supplementary Fig. 24 kuti mudziwe zambiri).
Ponseponse, pa Ni(OH)2-NS (Chithunzi 3h, pamwamba), gawo lochepetsa pang'onopang'ono kuchokera ku gawo la Ni(OH)2 kupita ku gawo la NiOOH lingagwiritsidwe ntchito ngati RDS ya njira yonse ya COR m'malo mwa gawo la mankhwala la kapangidwe ka AA kuchokera ku cyclohexanone panthawi yochepetsa mankhwala a NiOOH. Pa NiV-LDH-NS (Chithunzi 3h, pansi), kusintha kwa V kumawonjezera kinetics ya okosijeni ya Ni2+ kukhala Ni3+x, motero kumafulumizitsa kupanga kwa NiVOOH (m'malo mogwiritsa ntchito mankhwala ochepetsa), zomwe zimasuntha RDS kupita ku gawo la mankhwala. Kuti timvetse kukonzanso kwa Ni komwe kumayambitsidwa ndi kusintha kwa V, tinachita mawerengedwe ena a chiphunzitso. Monga momwe tawonetsera pa Chithunzi 3h, tinatsanzira njira yokonzanso ya Ni(OH)2-NS ndi NiV-LDH-NS. Magulu a lattice hydroxyl pa Ni(OH)2-NS ndi NiV-LDH-NS amachotsedwa potulutsa OH- mu electrolyte kuti apange mpweya wa lattice wopanda ma electron. Machitidwe ofanana a mankhwala ndi awa:
Kusintha kwa mphamvu ya Gibbs yopanda mphamvu pakukonzanso kunawerengedwa (Chithunzi 3i), ndipo NiV-LDH-NS (0.81 eV) inawonetsa kusintha kochepa kwambiri kwa mphamvu ya Gibbs yopanda mphamvu kuposa Ni(OH)2-NS (1.66 eV), zomwe zikusonyeza kuti kusintha kwa V kunachepetsa mphamvu yamagetsi yofunikira pakukonzanso kwa Ni. Tikukhulupirira kuti kulimbikitsa kukonzanso kungachepetse chotchinga cha mphamvu cha COR yonse (onani kafukufuku wa reaction mechanism pansipa kuti mudziwe zambiri), motero kufulumizitsa reaction pa kuchuluka kwa mphamvu yamagetsi.
Kusanthula komwe kwatchulidwa pamwambapa kukuwonetsa kuti kusintha kwa V kumayambitsa kukonzanso mwachangu kwa Ni(OH)2, motero kumawonjezera kuchuluka kwa reaction komanso, kuchuluka kwa COR current. Komabe, malo a Ni3+x amathanso kulimbikitsa ntchito ya OER. Kuchokera ku LSV curve yopanda cyclohexanone, zikuwoneka kuti kuchuluka kwa NiV-LDH-NS ndi kwakukulu kuposa kwa Ni(OH)2-NS (Chithunzi Chowonjezera 19), zomwe zimapangitsa kuti zochita za COR ndi OER zipange zochitika zopikisana. Chifukwa chake, FE yayikulu kwambiri ya AA kuposa ya NiV-LDH-NS siyingathe kufotokozedwa mokwanira ndi kusintha kwa V komwe kumalimbikitsa kukonzanso gawo.
Kawirikawiri amavomerezedwa kuti mu alkaline media, ma electrooxidation reactions a nucleophilic substrates nthawi zambiri amatsatira chitsanzo cha Langmuir-Hinshelwood (LH). Makamaka, substrate ndi OH− anions zimagwirizanitsidwa bwino pamwamba pa catalyst, ndipo OH− yolumikizidwa imasinthidwa kukhala magulu a hydroxyl (OH*), omwe amagwira ntchito ngati ma electrophiles oxidation a nucleophiles, njira yomwe yawonetsedwa kale ndi deta yoyesera ndi/kapena mawerengedwe a theoretical45,46,47. Chifukwa chake, kuchuluka kwa ma reactants ndi chiŵerengero chawo (organic substrate ndi OH−) kumatha kuwongolera kuphimba kwa reactant pamwamba pa catalyst, motero kumakhudza FE ndi zokolola za chinthu chomwe chikufunidwa14,48,49,50. Pankhani yathu, tikuganiza kuti kuphimba kwakukulu kwa cyclohexanone mu NiV-LDH-NS kumakonda njira ya COR, ndipo mosiyana, kuphimba kochepa kwa cyclohexanone mu Ni(OH)2-NS kumakonda njira ya OER.
Kuti tiyese lingaliro lomwe lili pamwambapa, choyamba tinachita mayeso awiri okhudzana ndi kuchuluka kwa ma reactants (C, cyclohexanone, ndi COH−). Kuyesa koyamba kunachitika ndi electrolysis pa mphamvu yokhazikika (1.8 VRHE) pa ma catalyst a Ni(OH)2-NS ndi NiV-LDH-NS okhala ndi zinthu zosiyanasiyana za cyclohexanone C (0.05 ~ 0.45 M) ndi COH− yokhazikika (0.5 M). Kenako, kupanga kwa FE ndi AA kunawerengedwa. Pa catalyst ya NiV-LDH-NS, ubale pakati pa AA yield ndi cyclohexanone C unawonetsa "mtundu wa volcanic" curve wamba mu LH mode (Chithunzi 4a), zomwe zikusonyeza kuti kufalikira kwa cyclohexanone kwakukulu kumapikisana ndi OH− adsorption. Ngakhale pa Ni(OH)2-NS, phindu la AA linawonjezeka pang'onopang'ono ndi kuwonjezeka kwa C ya cyclohexanone kuchokera pa 0.05 mpaka 0.45 M, zomwe zikusonyeza kuti ngakhale kuchuluka kwa cyclohexanone kunali kwakukulu (0.45 M), kuphimba kwake pamwamba kunali kotsika. Kuphatikiza apo, ndi kuwonjezeka kwa COH− mpaka 1.5 M, "mtundu wa volcanic" curve idawonedwa pa Ni(OH)2-NS kutengera C ya cyclohexanone, ndipo inflection point ya magwiridwe antchito idachedwa poyerekeza ndi NiV-LDH-NS, zomwe zikuwonetsanso kuti cyclohexanone imayamwa pang'ono pa Ni(OH)2-NS (Chithunzi Chowonjezera 25a ndi Chidziwitso 5). Kuphatikiza apo, FE ya AA pa NiV-LDH-NS inali yovuta kwambiri ku C-cyclohexanone ndipo inawonjezeka mofulumira kufika pa 80% pamene C-cyclohexanone inawonjezeka kuchoka pa 0.05 M kufika pa 0.3 M, zomwe zikusonyeza kuti cyclohexanone inali yowonjezereka mosavuta pa NiV-LDH-NS (Chithunzi 4b). Mosiyana ndi zimenezi, kuwonjezera kuchuluka kwa C-cyclohexanone sikunalepheretse kwambiri OER pa Ni(OH)2-NS, zomwe zingakhale chifukwa cha kusakwanira kwa cyclohexanone. Mosiyana ndi zimenezi, kufufuza kwina kokhudza kudalira kwa COH− pa mphamvu ya catalytic kunatsimikiziranso kuti kusamutsa kwa cyclohexanone kunakula poyerekeza ndi NiV-LDH-NS, yomwe ingathe kupirira COH− yambiri panthawi ya COR popanda kuchepetsa FE ya AA (Chithunzi Chowonjezera 25b, c ndi Zindikirani 5).
Kupanga kwa AA ndi EF ya b Ni(OH)2-NS ndi NiV-LDH-NS pa cyclohexanone yokhala ndi C yosiyana mu 0.5 M KOH. c Mphamvu zokoka za cyclohexanone pa NiOOH ndi NiVOOH. d FE ya AA pa Ni(OH)2-NS ndi NiV-LDH-NS mu 0.5 M KOH ndi 0.4 M cyclohexanone pa 1.80 VRHE pogwiritsa ntchito njira zokhazikika komanso zosasinthika. Mipiringidzo yolakwika ikuyimira kupotoka kwa miyezo itatu yodziyimira payokha pogwiritsa ntchito chitsanzo chomwecho ndipo ili mkati mwa 10%. e Pamwamba: Pa Ni(OH)2-NS, cyclohexanone yokhala ndi malo otsika C imakokedwa pang'ono ndi cyclohexanone, zomwe zimapangitsa kuti pakhale mpikisano wamphamvu wa OER. Pansi: Pa NiV-LDH-NS, kuchuluka kwa cyclohexanone C pamalo okwera kumawonedwa ndi kuchuluka kwa cyclohexanone, zomwe zimapangitsa kuti OER ichepetse. Deta yosaphika ya a–d imaperekedwa mu fayilo yosaphika ya data.
Kuti tiyese kukwezedwa kwa cyclohexanone pa NiV-LDH-NS, tinagwiritsa ntchito electrochemical coupled quartz crystal microbalance (E-QCM) kuti tiwone kusintha kwa mitundu ya adsorbed nthawi yeniyeni. Zotsatira zake zinasonyeza kuti mphamvu yoyamba ya adsorption ya cyclohexanone pa NiV-LDH-NS inali yayikulu nthawi 1.6 kuposa ya pa Ni(OH)2-NS mu mkhalidwe wa OCP, ndipo kusiyana kumeneku kwa mphamvu ya adsorption kunakula kwambiri pamene mphamvuyo inakula kufika pa 1.5 VRHE (Chithunzi Chowonjezera 26). Mawerengedwe a DFT ozungulira-polarized adachitidwa kuti afufuze momwe cyclohexanone imakwezera pa NiOOH ndi NiVOOH (Chithunzi 4c). Cyclohexanone imalowa mu Ni-center pa NiOOH ndi mphamvu ya adsorption (Eads) ya -0.57 eV, pomwe cyclohexanone imatha kulowa mu Ni-center kapena V-center pa NiVOOH, komwe V-center imapereka Eads yotsika kwambiri (-0.69 eV), mogwirizana ndi adsorption yamphamvu ya cyclohexanone pa NiVOOH.
Kuti titsimikizire kuti kukwezedwa kwa cyclohexanone kungathandize kupanga AA ndikuletsa OER, tinagwiritsa ntchito njira yochepetsera mphamvu kuti tiwonjezere cyclohexanone pamwamba pa catalyst (ya Ni(OH)2-NS ndi NiV-LDH-NS), zomwe zidachokera ku malipoti am'mbuyomu. 51, 52 Mwachindunji, tinagwiritsa ntchito mphamvu ya 1.8 VRHE ku COR, kenako tinasintha kukhala OCP state, kenako tinasintha kukhala 1.8 VRHE. Pankhaniyi, cyclohexanone imatha kudziunjikira pamwamba pa catalyst mu OCP state pakati pa electrolyses (onani gawo la Njira kuti mudziwe zambiri). Zotsatira zake zasonyeza kuti pa Ni(OH)2-NS ndi NiV-LDH-NS, kugwiritsa ntchito discontinuous potential electrolysis kunathandiza kuti catalytic performance iyende bwino poyerekeza ndi constant potential electrolysis (Chithunzi 4d). Chodziwika bwino n'chakuti, Ni(OH)2-NS inasonyeza kusintha kwakukulu mu COR (AA FE: kuchokera pa 51% mpaka 82%) ndi kuletsa OER (O2 FE: kuchokera pa 27% mpaka 4%) kuposa NiV-LDH-NS, zomwe zinayambitsidwa ndi mfundo yakuti kuchuluka kwa cyclohexanone kumatha kukonzedwa bwino kwambiri pa catalyst yokhala ndi mphamvu yofooka ya adsorption (monga, Ni(OH)2-NS) pogwiritsa ntchito electrolysis yokhazikika.
Ponseponse, kuletsa kwa OER pa NiV-LDH-NS kungayambitsidwe ndi kuwonjezeka kwa kulowetsedwa kwa cyclohexanone (Chithunzi 4e). Pa Ni(OH)2-NS (Chithunzi 4e, pamwamba), kulowetsedwa kochepa kwa cyclohexanone kunapangitsa kuti cyclohexanone ikhale yochepa komanso kuti OH* ikhale yochuluka pamwamba pa catalyst. Chifukwa chake, mitundu ya OH* yochulukirapo idzapangitsa kuti pakhale mpikisano waukulu wa OER ndikuchepetsa FE ya AA. Mosiyana ndi zimenezi, pa NiV-LDH-NS (Chithunzi 4e, pansi), kusintha kwa V kunawonjezera mphamvu ya cyclohexanone yolowetsedwa, motero kuwonjezera pamwamba pa C ya cyclohexanone ndikugwiritsa ntchito bwino mitundu ya OH* yolowetsedwa ya COR, kulimbikitsa kupanga kwa AA ndikuletsa OER.
Kuwonjezera pa kufufuza momwe kusintha kwa V kumakhudzira kukonzanso kwa mitundu ya Ni ndi cyclohexanone adsorption, tinafufuzanso ngati V imasintha njira yopangira AA kuchokera ku COR. Njira zingapo zosiyanasiyana za COR zaperekedwa m'mabuku, ndipo tinasanthula kuthekera kwawo mu dongosolo lathu la reaction (onani Supplementary Fig. 27 ndi Supplementary Note 6 kuti mudziwe zambiri)13,14,26. Choyamba, zanenedwa kuti gawo loyamba la njira ya COR lingakhale ndi okosijeni yoyamba ya cyclohexanone kuti ipange key intermediate 2-hydroxycyclohexanone (2)13,14. Kuti titsimikizire njirayi, tinagwiritsa ntchito 5,5-dimethyl-1-pyrrolidine N-oxide (DMPO) kuti tigwire intermediates yogwira ntchito yomwe imakhudzidwa pamwamba pa catalyst ndikuphunzira EPR. Zotsatira za EPR zidawonetsa kukhalapo kwa ma radicals a C-centered (R) ndi ma hydroxyl radicals (OH) pa ma catalyst onse awiri panthawi ya COR, zomwe zikusonyeza kuti Cα − H dehydrogenation ya cyclohexanone imapanga radical yapakati ya enolate (1), yomwe imawonjezedwanso ndi OH* kuti ipange 2 (Chithunzi 5a ndi Chithunzi Chowonjezera 28). Ngakhale kuti ma intermediates omwewo adapezeka pa ma catalyst onse awiri, gawo la dera la chizindikiro cha R pa NiV-LDH-NS linali lalikulu kuposa la Ni(OH)2-NS, lomwe lingakhale chifukwa cha mphamvu yowonjezera ya cyclohexanone (Table Yowonjezera 3 ndi Chidziwitso 7). Tinagwiritsanso ntchito 2 ndi 1,2-cyclohexanedione (3) ngati ma reactants oyambira a electrolysis kuti tiyese ngati V ingasinthe gawo lotsatira la oxidation. Zotsatira za electrolysis za potential intermediates (2 ndi 3) pa Ni(OH)2-NS ndi NiV-LDH-NS zasonyeza kusankhidwa kofanana kwa zinthu, zomwe zikusonyeza kuti COR reaction pa Ni(OH)2-NS kapena NiV-LDH-NS idapitilira m'njira zofanana (Chithunzi 5b). Komanso, AA inali chinthu chachikulu pokhapokha 2 itagwiritsidwa ntchito ngati reactant, zomwe zikusonyeza kuti AA idapezeka kudzera mu njira yowongoka mwachindunji kudzera mu kugawanika kwa Cα − Cβ bond ya 2 m'malo mwa oxidation yotsatira ku 3 pa ma catalyst onse awiri, popeza idasinthidwa kwambiri kukhala GA pomwe 3 idagwiritsidwa ntchito ngati reactant yoyambira (Zithunzi Zowonjezera 29, 30).
Chizindikiro cha EPR cha NiV-LDH-NS mu 0.5 M KOH + 0.4 M cyclohexanone. b Zotsatira za kusanthula kwa electrocatalytic kwa 2-hydroxycyclohexanone (2) ndi 1,2-cyclohexanedione (3). Electrolysis idachitika mu 0.5 M KOH ndi 0.1 M 2 kapena 3 pa 1.8 VRE kwa ola limodzi. Mipiringidzo yolakwika ikuyimira kupotoka kwa muyezo wa miyeso iwiri yodziyimira payokha pogwiritsa ntchito chothandizira chomwecho. c Njira zoyeserera za COR pa zothandizila ziwirizi. d Chithunzi chojambulidwa cha njira ya COR pa Ni(OH)2-NS (kumanzere) ndi d NiV-LDH-NS (kumanja). Mivi yofiira ikuwonetsa masitepe omwe kusintha kwa V kumathandizira mu njira ya COR. Deta yaiwisi ya a ndi b imaperekedwa mu fayilo ya data yaiwisi.
Ponseponse, tawonetsa kuti Ni(OH)2-NS ndi NiV-LDH-NS zimathandizira COR kudzera munjira yofanana: cyclohexanone imayamwa pamwamba pa catalyst, imachotsedwa mu hydrogen ndikutaya ma elekitironi kuti apange 1, yomwe kenako imasungunuka ndi OH* kuti ipange 2, kutsatiridwa ndi kusintha kwa magawo ambiri kuti ipange AA (Chithunzi 5c). Komabe, pamene cyclohexanone idagwiritsidwa ntchito ngati reactant, mpikisano wa OER unkawonedwa pa Ni(OH)2-NS yokha, pomwe mpweya wochepa kwambiri unasonkhanitsidwa pamene 2 ndi 3 zidagwiritsidwa ntchito ngati reactants. Chifukwa chake, kusiyana komwe kudawonedwa mu catalytic performance kungakhale chifukwa cha kusintha kwa RDS energy barrier ndi cyclohexanone adsorption capacity komwe kumachitika chifukwa cha kusintha kwa V m'malo mwa kusintha kwa reaction pathway. Chifukwa chake tidasanthula RDS ya reaction pathway pa catalysts zonse ziwiri. Zotsatira za X-ray acoustic spectroscopy zomwe zatchulidwa pamwambapa zikusonyeza kuti kusintha kwa V kumasintha RDS mu COR reaction kuchokera pa sitepe yokonzanso kupita ku sitepe ya mankhwala, kusunga gawo la NiOOH ndi mitundu ya Ni yapamwamba kwambiri pa NiV-LDH-NS (Chithunzi 3f, Chithunzi Chowonjezera 24, ndi Chidziwitso 4). Tinafufuzanso njira zochitira zomwe zimayimiridwa ndi kuchuluka kwa current mu gawo lililonse la madera osiyanasiyana omwe angatheke panthawi yoyezera CV (onani Chithunzi Chowonjezera 31 ndi Chidziwitso 8 kuti mudziwe zambiri) ndipo tinachita zoyeserera za H/D kinetic isotope exchange, zomwe zinawonetsa pamodzi kuti RDS ya COR pa NiV-LDH-NS imaphatikizapo kugawanika kwa Cα − H bond mu sitepe ya mankhwala osati gawo lochepetsera (onani Chithunzi Chowonjezera 32 ndi Chidziwitso 8 kuti mudziwe zambiri).
Kutengera ndi kusanthula komwe kwatchulidwa pamwambapa, zotsatira zonse za kusintha kwa V zawonetsedwa mu Chithunzi 5d. Ma catalyst a Ni(OH)2-NS ndi NiV-LDH-NS amapangidwanso pamwamba pa mphamvu zambiri za anodic ndipo amayendetsa COR kudzera munjira yofanana. Pa Ni(OH)2-NS (Chithunzi 5d, kumanzere), gawo lokonzanso ndi RDS panthawi ya COR; pomwe pa NiV-LDH-NS (Chithunzi 5d, kumanja), kusintha kwa V kunafulumizitsa kwambiri njira yokonzanso ndikusintha RDS kukhala Cα−H dehydrogenation ya cyclohexanone kuti ipange 1. Kuphatikiza apo, kulowetsedwa kwa cyclohexanone kunachitika pamalo a V ndipo kunakulitsidwa pa NiV-LDH-NS, zomwe zinathandizira kuletsa OER.
Poganizira za mphamvu yabwino kwambiri ya NiV-LDH-NS yokhala ndi FE yayikulu pamlingo wosiyanasiyana, tinapanga MEA kuti tikwaniritse kupanga kosalekeza kwa AA. MEA idasonkhanitsidwa pogwiritsa ntchito NiV-LDH-NS ngati anode, PtRu/C yamalonda ngati cathode53 ndi nembanemba yosinthira anion (mtundu: FAA-3-50) (Chithunzi 6a ndi Chithunzi Chowonjezera 33)54. Popeza magetsi a selo adachepa ndipo FE ya AA inali yofanana ndi 0.5 M KOH mu kafukufuku wapamwambawu, kuchuluka kwa anolyte kunakonzedwa kukhala 1 M KOH (Chithunzi Chowonjezera 25c). Ma curve a LSV olembedwa akuwonetsedwa mu Chithunzi Chowonjezera 34, zomwe zikusonyeza kuti mphamvu ya COR ya NiV-LDH-NS ndi yayikulu kwambiri kuposa ya Ni(OH)2-NS. Pofuna kusonyeza kupambana kwa NiV-LDH-NS, electrolysis yamagetsi yokhazikika idachitika ndi kuchuluka kwamagetsi kuyambira 50 mpaka 500 mA cm−2 ndipo magetsi ofanana ndi a cell adalembedwa. Zotsatira zake zidawonetsa kuti NiV-LDH-NS idawonetsa magetsi a cell a 1.76 V pa kuchuluka kwamagetsi a 300 mA cm−2, omwe anali otsika pafupifupi 16% kuposa a Ni(OH)2-NS (2.09 V), zomwe zikusonyeza kuti imagwiritsa ntchito mphamvu zambiri popanga AA (Chithunzi 6b).
Chithunzi cha batire yoyendera. b Voltage ya selo yopanda iR yolipirira pa Ni(OH)2-NS ndi NiV-LDH-NS mu 1 M KOH ndi 0.4 M cyclohexanone pa kachulukidwe kosiyanasiyana ka current. c AA ndi FE zimachokera pa Ni(OH)2-NS ndi NiV-LDH-NS pa kachulukidwe kosiyanasiyana ka current. Mipiringidzo yolakwika ikuyimira kupotoka kwa muyezo wa miyeso iwiri yodziyimira payokha pogwiritsa ntchito chothandizira chomwecho. d Kuyerekeza magwiridwe antchito a catalytic a ntchito yathu ndi machitidwe ena a batire yoyendera omwe anenedwa14,17,19. Ma parameter a reaction ndi makhalidwe a reaction alembedwa mwatsatanetsatane mu Supplementary Table 2. e Voltage ya selo ndi FE ya AA pa NiV-LDH-NS pa 200 ndi 300 mA cm−2 mu mayeso a nthawi yayitali, motsatana. Deta yaiwisi ya be imaperekedwa ngati fayilo ya data yaiwisi.
Pakadali pano, monga momwe zasonyezedwera mu Chithunzi 6c, NiV-LDH-NS kwenikweni idasunga FE yabwino (83% mpaka 61%) pamlingo wapamwamba wamagetsi (200 mpaka 500 mA cm-2), motero idakweza kupanga kwa AA (1031 mpaka 1900 μmol cm-2 h-1). Pakadali pano, 0.8% yokha ya anions a adipic acid idawonedwa mu cathode compartment pambuyo pa electrolysis, zomwe zikusonyeza kuti kusintha kwa cyclohexanone sikunali kofunikira kwambiri kwa ife (Chithunzi Chowonjezera 35). Mosiyana ndi izi, ndi kuchuluka komweko kwa kuchuluka kwamagetsi, FE ya AA pa Ni(OH)2-NS idatsika kuchoka pa 61% mpaka 34%, zomwe zidapangitsa kuti zikhale zovuta kukonza kupanga kwa AA (762 mpaka 1050 μmol cm-2 h-1). Makamaka, magwiridwe antchito a AA adachepa pang'ono chifukwa cha mpikisano wamphamvu wochokera ku OER, motero FE ya AA idatsika kwambiri ndi kuwonjezeka kwa kuchuluka kwa mphamvu zamagetsi (kuchokera pa 200 mpaka 250 mA cm−2, Chithunzi Chowonjezera 5). Monga momwe tikudziwira, zotsatira za catalytic pogwiritsa ntchito MEA ndi ma catalyst a NiV-LDH-NS zimaposa kwambiri magwiridwe antchito a ma flow reactors omwe adanenedwa kale ndi ma catalyst okhala ndi Ni (Table Yowonjezera 2). Komanso, monga momwe zasonyezedwera mu Chithunzi 6d, NiV-LDH-NS idawonetsa zabwino zazikulu pankhani ya kuchuluka kwa mphamvu zamagetsi zamagetsi, magetsi a maselo, ndi FE ya AA poyerekeza ndi catalyst yochokera ku Co yomwe imagwira ntchito bwino kwambiri, mwachitsanzo, Co3O4 yothandizidwa ndi graphene (Co3O4/GDY)17. Kuphatikiza apo, tinayesa momwe mphamvu imagwiritsidwira ntchito popanga AA ndipo tinawonetsa kuti mphamvu ya AA inali yotsika kwambiri, 2.4 W h gAA-1 yokha pamlingo wamakono wa 300 mA cm-2 ndi voteji ya selo ya 1.76 V (kuwerengera mwatsatanetsatane kwaperekedwa mu Supplementary Note 1). Poyerekeza ndi zotsatira zabwino kwambiri za 4.1 W h gAA-1 za Co3O4/GDY zomwe zanenedwa kale, mphamvu yogwiritsira ntchito popanga AA pantchito yathu idachepetsedwa ndi 42% ndipo zokolola zidawonjezeka ndi nthawi 4 (1536 vs. 319 μmol cm-2 h-1)17.
Kukhazikika kwa chothandizira cha NiV-LDH-NS cha kupanga AA kwa nthawi yayitali mu MEA kunayesedwa pa kuchuluka kwa 200 ndi 300 mA cm-2, motsatana (Chithunzi 6e). Popeza OH− imadyedwa mwachangu pa kuchuluka kwa current, kuchuluka kwa electrolyte pa 300 mA cm-2 ndi kwakukulu kuposa komwe kuli pa 200 mA cm-2 (onani gawo la "Kuyeza kwa Electrochemical" kuti mudziwe zambiri). Pa kuchuluka kwa 200 mA cm-2, kuchuluka kwa COR kunali 93% m'maola 6 oyamba, kenako kunatsika pang'ono kufika pa 81% pambuyo pa maola 60, pomwe magetsi a cell adakwera pang'ono ndi 7% (kuchokera pa 1.62 V mpaka 1.73 V), zomwe zikusonyeza kukhazikika kwabwino. Pamene kuchuluka kwa magetsi kukukwera kufika pa 300 mA cm−2, mphamvu ya AA sinasinthe kwenikweni (inatsika kuchoka pa 85% mpaka 72%), koma mphamvu ya magetsi ya selo inakwera kwambiri (kuchokera pa 1.71 mpaka 2.09 V, yofanana ndi 22%) panthawi ya mayeso a maola 46 (Chithunzi 6e). Tikuganiza kuti chifukwa chachikulu cha kuwonongeka kwa magwiridwe antchito ndi kuwonongeka kwa nembanemba yosinthira anion (AEM) ndi cyclohexanone, zomwe zimapangitsa kuti kukana kwa maselo ndi mphamvu ya magetsi ya selo ya electrolyzer kuchuluke (Chithunzi Chowonjezera 36), limodzi ndi kutuluka pang'ono kwa electrolyte kuchokera ku anode kupita ku cathode, zomwe zimapangitsa kuti kuchuluka kwa anolyte kuchepe komanso kufunika koyimitsa electrolysis. Kuphatikiza apo, kuchepa kwa FE kwa AA kungakhalenso chifukwa cha kuchotsedwa kwa ma catalyst, komwe kumathandizira kutsegulidwa kwa thovu la Ni la OER. Kuti tisonyeze momwe AEM yozimiririka imakhudzira kuwonongeka kwa kukhazikika pa 300 mA cm−2, tinayisintha ndi AEM yatsopano titatha maola 46 a electrolysis. Monga momwe tinkayembekezera, mphamvu ya catalytic inabwezeretsedwa bwino, ndi mphamvu ya selo ikuchepa kwambiri kufika pamtengo woyambirira (kuchokera pa 2.09 mpaka 1.71 V) kenako nkuwonjezeka pang'ono mkati mwa maola 12 otsatira a electrolysis (kuchokera pa 1.71 mpaka 1.79 V, kuwonjezeka kwa 5%; Chithunzi 6e).
Ponseponse, tinatha kupeza kukhazikika kwa AA kwa maola 60 pa kachulukidwe ka mphamvu ya 200 mA cm−2, zomwe zikusonyeza kuti FE ndi magetsi a maselo a AA zimasungidwa bwino. Tinayesanso kuchuluka kwa mphamvu ya 300 mA cm−2 ndipo tinapeza kukhazikika kwa mphamvu ya 58 h, m'malo mwa AEM ndi ina pambuyo pa maola 46. Maphunziro omwe ali pamwambawa akuwonetsa kukhazikika kwa chothandizira ndipo akuwonetsa momveka bwino kufunikira kwa chitukuko cha mtsogolo cha ma AEM amphamvu kwambiri kuti akonze kukhazikika kwa nthawi yayitali kwa MEA pakupanga kwa mphamvu ya AC kopitilira pa kachulukidwe ka mphamvu ya AC koyenera kwambiri.
Kutengera momwe MEA yathu imagwirira ntchito, tinapereka njira yonse yopangira AA kuphatikiza kudyetsa substrate, electrolysis, neutralization, ndi mayunitsi olekanitsa (Chithunzi Chowonjezera 37). Kusanthula koyambirira kwa magwiridwe antchito kunachitika kuti tiwone kuthekera kwachuma kwa dongosololi pogwiritsa ntchito chitsanzo cha alkaline electrolyte electrocatalytic carboxylate production 55. Pankhaniyi, ndalama zimaphatikizapo ndalama, ntchito, ndi zipangizo (Chithunzi 7a ndi Chithunzi Chowonjezera 38), ndipo ndalama zimachokera ku kupanga AA ndi H2. Zotsatira za TEA zikuwonetsa kuti pansi pa mikhalidwe yathu yogwirira ntchito (kuchuluka kwamakono 300 mA cm-2, voliyumu ya selo 1.76 V, FE 82%), ndalama zonse ndi ndalama ndi US $2429 ndi US $2564, motsatana, zomwe zimapangitsa kuti phindu likhale US $135 pa tani ya AA yopangidwa (onani Zowonjezera Chidziwitso 9 kuti mudziwe zambiri).
a Mtengo wonse wa njira yamagetsi ya AA pansi pa maziko a FE ya 82%, kuchuluka kwa current kwa 300 mA cm−2, ndi voliyumu ya selo ya 1.76 V. Kusanthula kwa sensitivity kwa ndalama zitatu ku b FE ndi c kuchuluka kwa current. Mu kusanthula kwa sensitivity, magawo ophunziridwa okha ndi omwe adasinthidwa ndipo magawo ena adasungidwa nthawi zonse kutengera chitsanzo cha TEA. d Zotsatira za FE yosiyana ndi kuchuluka kwa current pa phindu la AA electrosynthesis ndi phindu pogwiritsa ntchito Ni(OH)2-NS ndi NiV-LDH-NS, poganiza kuti voliyumu ya selo imasungidwa nthawi zonse pa 1.76 V. Deta yolowera ya a–d imaperekedwa mu fayilo ya data yaiwisi.
Kutengera ndi mfundo imeneyi, tinafufuzanso momwe FE ndi kuchuluka kwa magetsi zimakhudzira phindu la AA electrosynthesis. Tapeza kuti phindu limakhudzidwa kwambiri ndi FE ya AA, chifukwa kuchepa kwa FE kumabweretsa kuwonjezeka kwakukulu kwa mtengo wogwirira ntchito, motero kumawonjezera kwambiri mtengo wonse (Chithunzi 7b). Ponena za kuchuluka kwa magetsi, kuchuluka kwa magetsi (>200 mA cm-2) kumathandiza kuchepetsa mtengo wa ndalama zogwirira ntchito komanso mtengo womanga fakitale, makamaka pochepetsa dera la selo lamagetsi, motero kumathandizira kuwonjezeka kwa phindu (Chithunzi 7c). Poyerekeza ndi kuchuluka kwa magetsi, FE imakhudza kwambiri phindu. Pofotokoza momwe FE ndi kuchuluka kwa magetsi zimakhudzira phindu, tikuona bwino kufunika kopeza FE yapamwamba (>60%) pa kuchuluka kwa magetsi komwe kumafunikira m'mafakitale (>200 mA cm-2) kuti tiwonetsetse kuti phindu ndi lofunika. Chifukwa cha kuchuluka kwa FE kwa AA, njira yochitira zinthu ndi NiV-LDH-NS ngati chothandizira imakhalabe yabwino pakati pa 100–500 mA cm−2 (madontho a pentagram; Chithunzi 7d). Komabe, pa Ni(OH)2-NS, kuchepetsa FE pa kuchuluka kwa mphamvu zamagetsi (>200 mA cm−2) kunapangitsa kuti pakhale zotsatira zoyipa (mabwalo; Chithunzi 7d), zomwe zikuwonetsa kufunika kwa ma catalyst okhala ndi FE yapamwamba pa kuchuluka kwa mphamvu zamagetsi zamagetsi.
Kuwonjezera pa kufunika kwa zinthu zoyambitsa mavuto pochepetsa ndalama zogwirira ntchito ndi ndalama zogwirira ntchito, kuwunika kwathu kwa TEA kukuwonetsa kuti phindu likhoza kuwonjezeredwa m'njira ziwiri. Choyamba ndikugulitsa pamodzi potaziyamu sulfate (K2SO4) pamsika ngati chinthu chochokera ku unit yoletsa kuwononga, koma ndi ndalama zomwe zingabwereke za US$828/t AA-1 (Supplementary Note 9). Chachiwiri ndikukonza ukadaulo wokonza zinthu, kuphatikizapo kubwezeretsanso zinthu kapena kupanga ukadaulo wochepetsa kuwononga AA (njira zina zochepetsera kuwononga ndi kugawa). Njira yochepetsera kuwononga acid-base yomwe ikugwiritsidwa ntchito pano ikhoza kubweretsa ndalama zambiri pazinthu (zomwe zimawerengera gawo lalikulu pa 85.3%), zomwe 94% yake ndi chifukwa cha cyclohexanone ndi KOH ($2069/t AA-1; Chithunzi 7a), koma monga tafotokozera pamwambapa, njirayi ikadali yopindulitsa kwambiri. Tikupereka lingaliro lakuti ndalama zogulira zinthu zitha kuchepetsedwa kwambiri pogwiritsa ntchito njira zapamwamba kwambiri zobwezeretsera KOH ndi cyclohexanone yosakhudzidwa, monga electrodialysis kuti KOH14 ibwezeretsedwe kwathunthu (mtengo woyerekeza wa US$1073/t AA-1 kudzera mu electrodialysis; Zowonjezera 9).
Mwachidule, tinapeza mphamvu yayikulu ya electrolysis ya atomu ya aluminiyamu pamlingo wapamwamba wamagetsi poika V mu ma nanosheets a Ni(OH)2. Pansi pa 1.5–1.9 VRHE ndi kuchuluka kwamagetsi kwa 170 mA cm−2, AA FE pa NiV-LDH-NS inafika pa 83–88%, pomwe OER inachepetsedwa bwino kufika pa 3%. Kusintha kwa V kunathandizira kuchepetsa Ni2+ kukhala Ni3+x ndikuwonjezera kulowetsedwa kwa cyclohexanone. Deta yoyesera ndi yongopeka ikuwonetsa kuti kumangidwanso komwe kunalimbikitsidwa kumawonjezera kuchuluka kwamagetsi kwa cyclohexanone oxidation ndikusuntha RDS ya COR kuchokera pakumangidwanso kupita ku kuchotsedwa kwamadzimadzi komwe kumakhudzana ndi Cα − H scission, pomwe kulowetsedwa kwa cyclohexanone kumaletsa OER. Kukula kwa MEA kunapangitsa kuti AA ipangidwe mosalekeza pamlingo wamagetsi wa mafakitale wa 300 mA cm−2, mphamvu ya AA yodziwika bwino ya 82%, komanso kupanga kwa 1536 μmol cm−2 h−1. Kuyesa kwa maola 50 kunawonetsa kuti NiV-LDH-NS ili ndi kukhazikika kwabwino chifukwa imatha kusunga AA FE yapamwamba mu MEA (> 80% kwa maola 60 pa 200 mA cm−2; > 70% kwa maola 58 pa 300 mA cm−2). Tiyenera kudziwa kuti pakufunika kupanga ma AEM amphamvu kwambiri kuti akwaniritse kukhazikika kwanthawi yayitali pamlingo wamagetsi woyenera mafakitale. Kuphatikiza apo, TEA ikuwonetsa zabwino zachuma za njira zochitira zinthu popanga AA komanso kufunika kwa ma catalyst apamwamba komanso ukadaulo wapamwamba wolekanitsa kuti achepetse ndalama.