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Okusengejja asidi wa adipic (ekisookerwako kya nayirooni 66) okuva mu mafuta ga CA (omutabula gwa cyclohexanone ne cyclohexanol) nkola ya lubeerera eyinza okudda mu kifo ky’enkola ez’ennono ezeetaaga embeera enkambwe. Naye, density ya current entono n’ensengekera z’enkulaakulana ya okisigyeni ezivuganya zikoma nnyo ku nkola zaayo mu makolero. Mu mulimu guno, tukyusa nickel double hydroxide ne vanadium okutumbula density ya current n’okukuuma efficiency ya faradaic eya waggulu (>80%) ku potential range empanvu (1.5–1.9 V vs. reversible hydrogen electrode). Okunoonyereza okw’okugezesa n’okulowooza kwalaga emirimu ebiri emikulu egy’okukyusa V, omuli okuddamu okuzimba amangu ekirungo ekiziyiza n’okulongoosa mu kuyungibwa kwa cyclohexanone. Nga obukakafu bw’endowooza, twazimba ekibiina kya membrane-electrode ekyakola asidi wa adipic n’obulungi bwa faradaic obw’amaanyi (82%) n’obulungi (1536 μmol cm-2 h-1) ku density ya kasasiro ekwatagana n’amakolero (300 mA cm-2), ate nga tutuuka ku butebenkevu >50 h. Omulimu guno gulaga ekirungo ekikola obulungi eky’okusengejja amasannyalaze mu asidi wa adipic nga kirimu ebibala bingi n’obusobozi bw’amakolero.
Adipic acid (AA) y’emu ku asidi za aliphatic dicarboxylic ezisinga obukulu era esinga kukozesebwa mu kukola nayirooni 66 ne polyamides oba polymers endala1. Mu makolero, AA ekolebwa nga efuumuula omutabula gwa cyclohexanol ne cyclohexanone (kwe kugamba, amafuta ga AA) nga tukozesa 50–60 vol% nitric acid nga oxidizing agent. Enkola eno erina okweraliikirira kw’obutonde bw’ensi okukwatagana n’okufulumya asidi wa nayitiriki omungi ne nayitrojeni okisayidi (N2O ne NOx) nga ggaasi ezifuula obutonde bw’ensi2,3. Newankubadde nga H2O2 esobola okukozesebwa ng’ekirungo ekirala ekifuula omukka gwa green oxidizing agent, ssente zaayo ennene n’embeera zaayo enkambwe ez’okusengejja zikaluubiriza okukozesebwa mu nkola, era enkola esinga okukekkereza ssente n’okuwangaala yeetaagibwa4,5,6.
Mu myaka kkumi egiyise, enkola z’okusengejja eddagala n’amafuta mu masanyalaze zisikiriza okweyongera okuva mu bannassaayansi olw’ebirungi byabwe eby’okukozesa amaanyi agazzibwawo n’okukola mu mbeera enzibu (okugeza, ebbugumu ly’ekisenge ne puleesa y’ekifo)7,8,9,10. Mu nsonga eno, okukulaakulanya okukyusa amafuta ga KA okudda mu AA mu ngeri y’amasannyalaze kikulu nnyo okufuna ebirungi ebyo waggulu awamu n’okumalawo okukozesa asidi wa nitric acid ne nitrous oxide ebifulumizibwa ebisangibwa mu kukola okwa bulijjo (Ekifaananyi 1a). Omulimu gwa pioneering gwakolebwa Petrosyan et al., abaategeeza nti electrocatalytic oxidation reaction ya cyclohexanone (COR; cyclohexanone oba cyclohexanol ebadde emanyiddwa nnyo nga ekiikirira amafuta ga KA) ku nickel oxyhydroxide (NiOOH), naye density ya current entono (6 mA cm-2) n’amakungula ga AA ag’ekigero (52%) byali yafunibwa11,12. Okuva olwo, enkulaakulana ey’amaanyi ekoleddwa mu kukola ebirungo ebikola ebirungo ebiyitibwa nickel-based catalysts okutumbula emirimu gya COR. Okugeza, ekirungo ekiyitibwa copper-doped nickel hydroxide (Cu-Ni(OH)2) catalyst kyakolebwa okutumbula Cα–Cβ cleavage mu cyclohexanol13. Gye buvuddeko twategeeza ku Ni(OH)2 catalyst ekyakyusibwa ne sodium dodecyl sulfonate (SDS) okukola microenvironment etali ya mazzi egaggawaza cyclohexanone14.
a Okusoomoozebwa kw’okukola AA nga tuyita mu electrooxidation y’amafuta ga KA. b Okugerageranya electrocatalytic COR ya electrocatalytic COR ya Ni-based catalysts ezaategeezebwa emabegako ne catalyst yaffe mu nkola ya electrode ssatu n’enkola ya flow battery11,13,14,16,26. Amawulire mu bujjuvu ku bipimo by’ensengekera n’enkola y’ensengekera biweereddwa mu bipande eby’okugattako 1 ne 2. c Omulimu gw’okutabula (catalytic performance) ogw’ebirungo byaffe ebya NiV-LDH-NS ebya COR mu riyakita y’obutoffaali bwa H ne MEA, ebikola ku bbanga erigazi ery’obusobozi.
Newankubadde enkola ezo waggulu zalongoosa emirimu gya COR, ebirungo ebiyitibwa Ni-based catalysts ebyogeddwako byalaga obulungi bwa AA Faraday obw’amaanyi (FE) (>80%) ku potentials entono zokka, mu ngeri entuufu wansi wa 1.6 V bw’ogeraageranya n’ekyuma ekikyusa haidrojeni (RHE, ekifunze VRHE). Bwe kityo, density ya kasasiro ey’ekitundu eyaloopebwa (kwe kugamba, density ya current yonna ekubisibwamu FE) eya AA bulijjo eri wansi wa 60 mA cm−2 (Figure 1b and Supplementary Table 1). Densite ya current entono eri wansi nnyo w’ebyetaago by’amakolero (>200 mA cm−2)15, ekiziyiza ennyo tekinologiya wa electrocatalytic for high-throughput AA synthesis (Figure 1a; top). Okwongera ku density ya kasasiro, potensiya esingako obulungi (ku nkola ya obusannyalazo busatu) oba vvulovumenti y’obutoffaali eya waggulu (ku nkola ya busannyalazo bubiri) esobola okukozesebwa, nga eno nkola nnyangu eri enkyukakyuka nnyingi ez’obusannyalazo naddala enkola ya oxygen evolution reaction (OER). Naye ku COR ku busobozi bwa anodic obw’amaanyi, OER esobola okufuuka omuvuganya omukulu mu kukendeeza FE ya AA, bwe kityo n’ekendeeza ku kukozesa amaanyi amalungi (Ekifaananyi 1a; wansi). Okugeza, nga twetegereza enkulaakulana eyasooka (Figure 1b ne Supplementary Table 1), twaggwaamu essuubi okukizuula nti FE ya AA ku SDS-modified Ni(OH)2 yakendeera okuva ku 93% okutuuka ku 76% nga eyongera ku busobozi obukozesebwa okuva ku 1.5 VRHE okutuuka ku 1.7 VRHE14, ate FE ya AA ku CuxNi1-x(OH)2/CF yakendeera okuva ku 93% okutuuka ku 69% nga kwongera ku busobozi okuva ku 1.52 VRHE okutuuka ku 1.62 VRHE16. Bwe kityo, density ya kasasiro ey’ekitundu eyaloopebwa eya AA teyongera mu kigerageranyo ku potentials eza waggulu, ekisinga okukomya okulongoosa omulimu gwa AA, nga tetugambye ku nkozesa y’amasoboza amangi olw’FE entono eya AA. Ng’oggyeeko ebirungo ebikola nickel, ebirungo ebikola kobalti nabyo biraga omulimu gw’okutabula mu COR17,18,19. Naye, obulungi bwazo bukendeera ku busobozi obusingako, era bw’ogeraageranya n’ebiziyiza ebikolebwa mu Ni, zirina obuzibu obusingako mu kukola mu makolero, gamba ng’okukyukakyuka kw’emiwendo okunene n’ebintu ebitono. N’olwekyo, kyetaagisa okukola ebiziyiza ebisinziira ku Ni ebirina density ya current enkulu ne FE mu COR okukifuula eky’omugaso okutuuka ku makungula ga AA amangi.
Mu mulimu guno, tutegeeza vanadium (V)-modified nickel layered double hydroxide nanosheets (NiV-LDH-NS) nga efficient electrocatalysts for AA production nga bayita mu COR, ezikola ku wide potential range ne significantly suppressed OER, okutuuka ku high FE ne current density mu byombi H-obutoffaali ne membrane electrode assemblies (MEAs; Ekifaananyi 1 b). Tusooka kulaga nti obulungi bwa acetylene oxidation ku typical Ni(OH)2 nanosheet catalyst (Ni(OH)2-NS) bukendeera, nga bwe kisuubirwa, ku potentials eza waggulu, okuva ku 80% ku 1.5 VRHE okutuuka ku 42% ku 1.9 VRHE. Mu njawulo nnyo, oluvannyuma lw’okukyusa Ni(OH)2 ne V, NiV-LDH-NS yalaga density ya current esingako ku potential eweereddwa era, ekisinga obukulu, yakuuma FE waggulu ku potential range empanvu. Okugeza, ku 1.9 VRHE, yalaga density ya current eya 170 mA cm−2 ne FE ya 83%, nga eno ye catalyst esinga obulungi eri COR mu nkola ya electrode ssatu (Fig. 1c ne Supplementary Table 1). Ebiwandiiko eby’okugezesa n’eby’enzikiriziganya biraga nti enkyukakyuka ya V etumbula kinetics y’okukendeeza okuva ku Ni(OH)2 okutuuka ku Ni oxyhydroxides eza valenti enkulu (Ni3+xOOH1-x), ezikola nga ekitundu ekikola ku COR. Ekirala, enkyukakyuka ya V yayongera okusikiriza kwa cyclohexanone ku ngulu w’ekirungo ekiziyiza, ekyakola kinene mu kunyigiriza OER ku busobozi bwa anodic obw’amaanyi. Okulaga obusobozi bwa NiV-LDH-NS mu mbeera esinga okuba entuufu, twakola dizayini ya MEA flow reactor era ne tulaga FE ya AA (82%) ku makolero agakwatagana current density (300 mA cm−2), nga eno esinga nnyo ku bivudde mu kunoonyereza kwaffe emabega mu membrane flow reactor (Fig. 1b ne Supplementary Table 2). Amakungula agakwatagana aga AA (1536 μmol cm−2 h−1) gaali gasinga n’ago agafunibwa nga tukozesa enkola ya thermal catalytic (<30 mmol gcatalyst−1 h−1)4. Ekirala, ekirungo ekiziyiza (catalyst) kyalaga obutebenkevu obulungi nga kikozesa MEA, nga kikuuma FE >80% AA okumala essaawa 60 ku 200 mA cm−2 ne FE >70% AA okumala essaawa 58 ku 300 mA cm−2. Mu kusembayo, okunoonyereza okusooka okukolebwa (FEA) kwalaga nti enkola ya electrocatalytic ekola AA ekendeeza ku nsimbi ezisaasaanyizibwa.
Okusinziira ku biwandiiko eby’emabega, Ni(OH)2 ye catalyst eya bulijjo eraga omulimu omulungi eri COR, kale Ni(OH)2-NS13,14 yasengekebwa omulundi ogwasooka nga tuyita mu nkola ya coprecipitation. Sampuli zalaga ensengekera ya β-Ni (OH) 2, eyakakasibwa n’okuwunyiriza kwa X-ray (XRD; Ekifaananyi 2a), era nanosheets ezigonvu ennyo (obugumu: 2-3 nm, obunene obw’ebbali: 20-50 nm) zaalabibwa n’okupima obusannyalazo obutambuza obusannyalazo obw’obulungi obw’amaanyi (HRTEM; Supplementary Fig. 1) n’okupima amaanyi ga atomu (AFM). (Ekifaananyi eky’okugattako. 2). Okugatta kwa nanosheets nakyo kyalabiddwa olw’obutonde bwazo obugonvu ennyo.
a enkola z’okuwunyiriza kwa X-ray eza Ni(OH)2-NS ne NiV-LDH-NS. FE, okuyita, ne AA density ya kasasiro ku b Ni(OH)2-NS ne c NiV-LDH-NS ku potentials ez’enjawulo. Embaawo z’ensobi zikiikirira okukyama okutuufu okw’ebipimo bisatu ebyetongodde nga tukozesa ekirungo kye kimu. d Ekifaananyi kya HRTEM ekya NV-LDH-NS. Ebbaala ya minzaani: 20 nm. Ekifaananyi kya HAADF-STEM ekya NiV-LDH-NS ne maapu ya elementi ekwatagana eraga ensaasaanya ya Ni (kijanjalo), V (emmyufu), ne O (bbulu). Ebbaala ya minzaani: 100 nm. f Ni 2p3/2, g O 1 s, ne h V 2p3/2 XPS data ya Ni(OH)2-NS (waggulu) ne NiV-LDH-NS (wansi). i FE ne j ze nkola za AA ku biziyiza ebibiri mu nsengekera 7. Embaawo z’ensobi zikiikirira okukyama okutuufu okw’ebipimo bisatu ebyetongodde nga tukozesa ekirungo kye kimu era nga biri mu bitundu 10%. Data embisi eya a–c ne f–j eweebwa mu fayiro za data embisi.
Olwo ne twekenneenya enkola ya Ni(OH)2-NS ku COR. Nga tukozesa constant potential electrolysis, twafuna 80% FE ya AA ku potential entono (1.5 VRHE) awatali OER (Figure 2b), ekiraga nti COR esinga amaanyi mu maanyi okusinga OER ku low anodic potentials. Ekikulu ekivaamu kyazuulibwa nga glutaric acid (GA) nga FE ya 3%. Okubeerawo kw’obungi obutonotono obwa asidi wa succinic (SA), asidi maloniki (MA), ne asidi oxalic (OA) nakyo kyapimibwa mu bungi mu HPLC (laba ekifaananyi eky’okugattako 3 okumanya engabanya y’ebintu). Tewali asidi ya formic yazuulibwa mu kivaamu, ekiraga nti kaboni ayinza okutondebwa ng’ekirungo kya C1. Okugezesa endowooza eno, ekisengejjero okuva mu kusengejja amasannyalaze okujjuvu okwa 0.4 M cyclohexanone kyafuulibwa asidi era ebiva mu ggaasi ne biyisibwa mu kisoolo kya Ca(OH)2. N’ekyavaamu, ekisengejjero kyafuuka ekiwujjo, ne kikakasa okutondebwa kwa kaboni oluvannyuma lw’okusengejja amasannyalaze. Naye olw’amasannyalaze omugatte amatono agakolebwa mu nkola y’okusengejja amasannyalaze (Ekifaananyi 2b, c), ekirungo kya kaboni kitono era kizibu okugera obungi. Okugatta ku ekyo, ebintu ebirala ebya C2-C5 nabyo biyinza okutondebwa, naye obungi bwabyo tebisobola kupimibwa. Newankubadde omuwendo gwonna ogw’ebintu kizibu okugera obungi, ebitundu 90% ku muwendo gwonna ogw’amasannyalaze ogw’enkanankana kiraga nti enkola z’amasannyalaze ezisinga obungi zizuuliddwa, ekituwa omusingi gw’okutegeera kwaffe okw’enkola. Olw’obuzito bwa kasasiro obutono (20 mA cm−2), amakungula ga AA gaali 97 μmol cm−2 h−1 (Ekifaananyi 2b), ekyenkana 19 mmol h−1 g−1 okusinziira ku kutikka obuzito bw’ekirungo ekiziyiza (5 mg cm−2), nga kino kiri wansi okusinga ebivaamu eby’ebbugumu (~30 mmol h−1 g−1)1. Bwe obusobozi obukozesebwa bweyongera okuva ku 1.5 okutuuka ku 1.9 VRHE, wadde nga density ya kasasiro okutwalira awamu yeeyongera (okuva ku 20 okutuuka ku 114 mA cm−2), mu kiseera kye kimu waaliwo okukendeera okw’amaanyi mu AA FE, okuva ku 80% okutuuka ku 42%. Okukendeera kwa FE ku potentials ezisingako obulungi okusinga kuva ku kuvuganya ku OER. Naddala ku 1.7 VRHE, okuvuganya kwa OER kuleeta okukendeera okw’amaanyi mu AA FE, bwe kityo ne kikendeeza katono ku mutindo gwa AA nga gweyongera ku density ya kasasiro okutwalira awamu. Bwe kityo, newankubadde nga ekitundu kya kasasiro density ya AA yeeyongera okuva ku 16 okutuuka ku 48 mA cm−2 era AA productivity yeeyongera (okuva ku 97 okutuuka ku 298 μmol cm−2 h−1), omuwendo omunene ogw’amasoboza ag’enjawulo gwakozesebwa (2.5 W h gAA−1 more okuva ku 1.5 okutuuka ku 1.9 VRHE), ekivaamu okweyongera mu carbon emissions ya 2.7 g CO2 gAA−1 (ebikwata ku kubala biweereddwa mu Supplementary Note 1). OER eyayogerwako emabegako ng’evuganya ne COR reaction ku high anodic potentials ekwatagana ne lipoota ezaaliwo emabega era ekiikirira okusoomoozebwa okwawamu okulongoosa AA productivity14,17.
Okukola ekintu ekikola obulungi ennyo ekya Ni(OH)2-NS-based COR catalyst, twasooka kwekenneenya ekitundu ekikola. Twalaba entikko ku 473 cm-1 ne 553 cm-1 mu bivudde mu Raman spectroscopy yaffe mu kifo (Supplementary Fig. 4), ebikwatagana n’okubeebalama n’okugolola ebiyungo bya Ni3 +-O mu NiOOH, mu kulondako. Kiwandiikiddwa nti NiOOH kiva mu kukendeera kwa Ni(OH)2 n’okukuŋŋaanyizibwa kwa Ni(OH)O ku potentials za anodic, era mu bukulu ye active phase mu electrocatalytic oxidation20,21. Nolwekyo, tusuubira nti okwanguya enkola y’okuddamu okuzimba phase ya Ni(OH)2 okutuuka ku NiOOH kiyinza okutumbula omulimu gw’okutabula COR.
Twagezaako okukyusa Ni(OH)2 n’ebyuma eby’enjawulo okuva lwe kyazuulibwa nti okukyusa heteroatomu kutumbula okuddamu okuzimba phase mu oxides/hydroxides ebyuma ebikyukakyuka22,23,24. Sampuli zasengekebwa nga ziteekebwa wamu ne Ni n’ekyuma ekyokubiri ekisookerwako. Mu sampuli ez’enjawulo ezikyusiddwa ebyuma, sampuli eyakyusiddwa V (V:Ni atomic ratio 1:8) (eyitibwa NiV-LDH-NS) yalaga density ya current esingako mu COR (Supplementary Fig. 5) ate ekisinga obukulu, AA FE waggulu ku ddirisa lya potential egazi. Okusingira ddala, ku potential entono (1.5 VRHE), density ya NiV-LDH-NS eya kati yali waggulu emirundi 1.9 okusinga eya Ni(OH)2-NS (39 vs. 20 mA cm−2), era AA FE yali egeraageranyizibwa ku catalysts zombi (83% vs. 80%). Olw’obungi bwa kasasiro obusingako n’okufaananako FE AA, ebibala bya NiV-LDH-NS biri waggulu emirundi 2.1 okusinga ebya Ni(OH)2-NS (204 vs. 97 μmol cm−2 h−1), ekiraga okutumbula ekikolwa ky’okukyusa V ku density ya kasasiro ku buziba obutono (Ekifaananyi 2c).
Nga eyongera ku potential ekozesebwa (okugeza, 1.9 VRHE), density ya current ku NiV-LDH-NS eri waggulu emirundi 1.5 okusinga ku Ni(OH)2-NS (170 vs. 114 mA cm−2), era okweyongera kufaananako n’okwo ku potentials eza wansi (emirundi 1.9 waggulu). Ekikulu, NiV-LDH-NS yasigaza AA FE enkulu (83%) era OER yali enyigirizibwa nnyo (O2 FE 4%; Ekifaananyi 2c), okusinga Ni (OH)2-NS era emabegako yaloopebwa catalysts ne AA FE wansi ennyo ku anodic potentials waggulu (Supplementary Table 1). Olw’okuba FE enkulu eya AA mu ddirisa ery’obusobozi obugazi (1.5–1.9 VRHE), omuwendo gw’okuzaala AA ogwa 867 μmol cm−2 h−1 (ogwenkana 174.3 mmol g−1 h−1) gwatuukibwako ku 1.9 VRHE, nga kiraga omulimu omulungi mu nkola za electrocatalytic ne wadde thermocatalytic ng’omulimu gufuuse gwa bulijjo olw’okutikka kw’amasasi kwonna okwa Sampuli za NiV-LDH-NS (Ekifaananyi eky’okugattako. 6).
Okutegeera density ya current enkulu ne FE enkulu ku potential range empanvu oluvannyuma lw’okukyusa Ni(OH)2 ne V, twalaga ensengeka ya NiV-LDH-NS. Ebivudde mu XRD biraga nti enkyukakyuka ne V yaleeta enkyukakyuka ya phase okuva ku β-Ni(OH)2 okudda mu α-Ni(OH)2, era tewali bika bya kirisitaalo ebikwatagana ne V byazuulibwa (Fig. 2a). Ebivudde mu HRTEM biraga nti NiV-LDH-NS esikira enkula ya ultrathin Ni(OH)2-NS nanosheets era erina ebipimo by’ebbali ebifaanagana (Fig. 2d). Ebipimo bya AFM byalaga omuze gw’okugatta ogw’amaanyi ogwa nanosheets, ekivaamu obuwanvu obupimibwa nga 7 nm (Supplementary Fig. 7), obunene okusinga obwa Ni(OH)2-NS (obugumu: 2-3 nm). Okwekenenya maapu ya Energy-dispersive X-ray spectroscopy (EDS) (Ekifaananyi 2e) kwalaga nti elementi za V ne Ni zasaasaanyizibwa bulungi mu nanosheets. Okusobola okunnyonnyola ensengekera y’obusannyalazo bwa V n’engeri gye kikwata ku Ni, twakozesa X-ray photoelectron spectroscopy (XPS) (Ekifaananyi 2f–h). Ni(OH)2-NS yalaga entikko z’enkulungo ez’enjawulo eza Ni2+ (entikko y’ekikazi ku 855.6 eV, entikko ya setilayiti ku 861.1 eV, Ekifaananyi 2f)25. O 1 s XPS spectrum ya Ni(OH)2-NS esobola okwawulwamu entikko ssatu, nga mu zino entikko eziri ku 529.9, 530.9 ne 532.8 eV ziteekebwa ku lattice oxygen (OL), hydroxyl group (Ni-OH) ne oxygen adsorbed on surface defects (OAds), respectively (Figure 2g)26,27,28,29. Oluvannyuma lw’okukyusa ne V, entikko ya V 2p3/2 yalabika, eyinza okuvunda mu ntikko ssatu ezisangibwa ku 517.1 eV (V5+), 516.6 eV (V4+) ne 515.8 eV (V3+), okusinziira ku, ekiraga nti ekika kya V mu nsengekera okusinga kiri mu mbeera za oxidation enkulu (Ekifaananyi 2h)25,30,31. Okugatta ku ekyo, entikko ya Ni 2p ku 855.4 eV mu NiV-LDH-NS yakyusibwa obubi (nga 0.2 eV) bw’ogeraageranya n’eyo mu Ni(OH)2-NS, ekiraga nti obusannyalazo bwakyusibwa okuva ku V okudda ku Ni. Embeera ya valensi entono ennyo eya Ni eyatunuuliddwa oluvannyuma lw’okukyusa V yali ekwatagana n’ebivudde mu Ni K-edge X-ray absorption near-edge spectroscopy (XANES) (laba ekitundu “V Modification Promotes Catalyst Reduction” wansi okumanya ebisingawo). NiV-LDH-NS oluvannyuma lw’okujjanjabwa COR okumala essaawa emu yategekebwa nga NiV-LDH-POST era yamanyibwa mu bujjuvu nga tukozesa transmission electron microscopy, EDS mapping, X-ray diffraction, Raman spectroscopy, n’okupima kwa XPS (Supplementary Figs. 8 and 9). Ebiziyiza byasigala nga ebikuŋŋaanyiziddwa nga birina enkula ya nanosheet ennyogovu ennyo (Supplementary Fig. 8a–c). Obuwundo bwa sampuli bwakendeera ate V ne bukendeera olw’okukulukuta kwa V n’okuddamu okuzimba ekirungo ekiziyiza (Supplementary Fig. 8d–f). XPS spectra zalaga okukendeera mu V peak intensity (Supplementary Fig. 9), nga kino kyava ku V leaching. Okugatta ku ekyo, okwekenneenya O 1s spectrum (Supplementary Fig. 9d) n’okupima electron paramagnetic resonance (EPR) (Supplementary Fig. 10) byalaga nti obungi bw’ebifo bya oxygen ku NiV-LDH-NS gweyongera oluvannyuma lwa 1 h of electrolysis, ekiyinza okuvaako enkyukakyuka embi mu Ni 2p binding energy (laba Supplementary Figs. 9 ne 10 okumanya ebisingawo ebikwata ku nsonga eno)26,27,32,33. Bwe kityo, NiV-LDH-NS yalaga enkyukakyuka entono mu nsengekera oluvannyuma lwa 1 h ya COR.
Okukakasa omulimu omukulu ogwa V mu kutumbula COR, twasengejja ebirungo ebiziyiza NiV-LDH ebirina emigerageranyo gya atomu egy’enjawulo egya V:Ni (1:32, 1:16, ne 1:4, egyalagirwa nga NiV-32, NiV-16, ne NiV-4, mu kulondako) okuggyako 1:8 mu nkola y’emu ey’okutonnya. Ebivudde mu kukola maapu ya EDS biraga nti omugerageranyo gwa atomu gwa V:Ni mu kiziyiza guli kumpi n’ogw’ekisookerwako (Supplementary Fig. 11a–e). Nga enkyukakyuka ya V yeeyongera, amaanyi g’ekisengejjo kya V 2p geeyongera, era amasoboza ag’okusiba ag’ekitundu kya Ni 2p gakyuka buli kiseera okudda ku ludda olubi (Ekifaananyi eky’okugattako 12). Mu kiseera kye kimu, ekitundu kya OL kyagenda kyeyongera mpolampola. Ebivudde mu kugezesebwa kwa catalytic biraga nti OER esobola okunyigirizibwa obulungi ne bwe kiba nga kikyusiddwa V ekitono (V:Ni atomic ratio of 1:32), nga O2 FE ekendeera okuva ku 27% okutuuka ku 11% ku 1.8 VRHE oluvannyuma lw’okukyusa V (Supplementary Fig. 11f). Olw’okweyongera kw’omugerageranyo gwa V:Ni okuva ku 1:32 okutuuka ku 1:8, omulimu gw’okutabula gweyongera. Naye, nga okwongera okweyongera kw’okukyusa V (V:Ni ratio of 1:4), density ya current ekendeera, kye tuteebereza nti kiva ku kukendeera mu density y’ebifo ebikola Ni (naddala NiOOH active phase; Supplementary Fig. 11f). Olw’okutumbula ekikolwa ky’okukyusa V n’okukuuma ebifo ebikola Ni, ekirungo ekiziyiza omugerageranyo gwa V:Ni 1:8 kyalaga omulimu gwa FE ne AA ogusinga obunene mu kugezesebwa okw’okukebera omugerageranyo gwa V:Ni. Okusobola okunnyonnyola oba omugerageranyo gwa V:Ni gusigala nga tegukyukakyuka oluvannyuma lw’okusengejja amasannyalaze, ebitonde by’ebirungo ebikozesebwa byalambikibwa. Ebivuddemu biraga nti ku biwujjo ebirina emigerageranyo gya V:Ni egyasooka okuva ku 1:16 okutuuka ku 1:4, omugerageranyo gwa V:Ni gwakendeera okutuuka ku nga 1:22 oluvannyuma lw’ensengekera, ekiyinza okuba nga kiva ku kukulukuta kwa V olw’okuddamu okuzimba ekirungo ekiziyiza (Supplementary Fig. 13). Weetegereze nti AA FEs ezigeraageranyizibwa zaalabibwa nga omugerageranyo gwa V: Ni ogwasooka gwenkana oba nga gusinga 1:16 (Supplementary Fig. 11f), ekiyinza okunnyonnyolwa okuddamu okuzimba ekirungo ekivaamu emigerageranyo gya V:Ni egy’enjawulo mu biwujjo ebiraga omulimu gw’okutabula ogugeraageranyizibwa.
Okwongera okukakasa obukulu bwa V-modified Ni(OH)2 mu kwongera ku mutindo gwa COR, twakola enkola endala bbiri ez’obutonde okuyingiza V mu bintu bya Ni(OH)2-NS. Emu nkola ya kutabula, era sampuli eyitibwa NiV-MIX; endala nkola ya kufuuwa amazzi mu mutendera, era sampuli eyitibwa NiV-SP. Ebikwata ku kugatta biweereddwa mu kitundu ky’Enkola. SEM-EDS mapping yalaga nti V yakyusibwa bulungi ku Ni(OH)2-NS surface ya samples zombi (Supplementary Fig. 14). Ebivudde mu kusengejja amasannyalaze biraga nti ku 1.8 VRHE, obulungi bwa AA ku busannyalazo bwa NiV-MIX ne NiV-SP buli 78% ne 79%, nga byombi biraga obulungi okusinga Ni(OH)2-NS (51%). Ekirala, OER ku NiV-MIX ne NiV-SP electrodes yanyigirizibwa (FE O2: 7% ne 2%, okusinziira ku) bw’ogeraageranya ne Ni(OH)2-NS (FE O2: 27%). Ebivuddemu bino bikakasa ekikolwa ekirungi eky’okukyusa V mu Ni(OH)2 ku kunyigirizibwa kwa OER (Supplementary Fig. 14). Naye, okutebenkera kw’ebirungo ebiziyiza (catalysts) kwali mu kabi, ekyalagibwa okukendeera kwa FE AA ku NiV-MIX okutuuka ku bitundu 45% ne ku NiV-SP okutuuka ku bitundu 35% oluvannyuma lw’enzirukanya za COR musanvu, ekitegeeza obwetaavu bw’okutwala enkola ezisaanidde okutebenkeza ebika bya V, gamba ng’okukyusa V mu lattice ya Ni(OH)2 mu NiV-LDH-NS, nga kino kye kisumuluzo ekikulu mu kino okukola.
Twekenneenya n’obutebenkevu bwa Ni(OH)2-NS ne NiV-LDH-NS nga tussa COR mu nsengekera eziwera. Enzirukanya yakolebwa okumala essaawa emu buli nsengekera era ekisengejjero kyakyusibwa oluvannyuma lwa buli nsengekera. Oluvannyuma lw’omutendera ogw’omusanvu, omulimu gwa FE ne AA ku Ni(OH)2-NS gwakendeera ebitundu 50% ne 60%, ate nga okweyongera mu OER kwalabiddwa (Fig. 2i, j). Oluvannyuma lwa buli cycle, twekenneenya cyclic voltammetry (CV) curves za catalysts ne tulaba nti oxidation peak ya Ni2+ yakendeera mpolampola, ekiraga okukendeera mu redox obusobozi bwa Ni (Supplementary Fig. 15a–c). Ng’oggyeeko okweyongera kw’obungi bwa Ni cation mu electrolyte mu kiseera ky’okusaanuusa (Supplementary Fig. 15d), tukwata ku kukendeera kw’omulimu (okukendeera kwa FE ne AA productivity) ku leaching ya Ni okuva mu catalyst, ekivaamu okubikkulwa okusingawo kwa Ni foamed substrate eyoleka OER activity. Okwawukana ku ekyo, NiV-LDH-NS yakendeeza ku kukendeera mu bibala bya FE ne AA okutuuka ku bitundu 10% (Fig. 2i, j), ekiraga nti enkyukakyuka ya V yaziyiza bulungi okukulukuta kwa Ni (Supplementary Fig. 15d). Okutegeera obutebenkevu obwongezeddwa mu nkyukakyuka ya V, twakola okubalirira okw’enzikiriziganya. Okusinziira ku biwandiiko eby’emabega34,35, enkyukakyuka ya entalpi y’enkola y’okuggya ekyuma mu atomu z’ebyuma ku ngulu ekola eya katalisi esobola okukozesebwa ng’ennyonnyola entuufu okwekenneenya obutebenkevu bw’ekirungo ekiziyiza. Nolwekyo, enkyukakyuka za entalpi y’enkola y’okuggya ebyuma mu atomu za Ni ku (100) kungulu kwa Ni(OH)2-NS ne NiV-LDH-NS (NiOOH ne NiVOOH, respectively) ezizzeemu okuzimbibwa zaali zibalirirwa (ebikwata ku nzimba y’ekyokulabirako byogerwako mu Supplementary Note 2 ne Supplementary Fig. 16). Enkola y’okuggya ebyuma mu Ni okuva mu NiOOH ne NiVOOH yalagibwa (Supplementary Fig. 17). Omuwendo gw’amasoboza ag’okuggya ekyuma ku NiVOOH (0.0325 eV) guli waggulu okusinga ku NiOOH (0.0005 eV), ekiraga nti okukyusa V kwongera ku butebenkevu bwa NiOOH.
Okukakasa OER inhibitory effect ku NiV-LDH-NS, naddala ku anodic potentials enkulu, differential electrochemical mass spectrometry (DEMS) yakolebwa okunoonyereza ku potential-dependent O2 formation ku sampuli ez’enjawulo. Ebivuddemu biraga nti mu butabeerawo cyclohexanone, O2 ku NiV-LDH-NS yalabika ku potential eyasooka eya 1.53 VRHE, nga eno yali wansi katono okusinga eya O2 ku Ni(OH)2-NS (1.62 VRHE) (Supplementary Fig. 18). Ekivaamu kino kiraga nti okuziyiza OER kwa NiV-LDH-NS mu kiseera kya COR kuyinza obutaba kuva ku mirimu gyayo egya OER emitono egy’omunda, ekikwatagana n’obungi bwa kasasiro obusingako katono mu linear sweep voltammetry (LSV) curves ku NiV-LDH-NS okusinga ku Ni(OH)2-NS awatali cyclohexanone (Supplementary Fig. 19). Oluvannyuma lw’okuleetebwa kwa cyclohexanone, okulwawo kw’enkulaakulana ya O2 (kiyinzika okuba nga kiva ku nkizo ya thermodynamic eya COR) kunnyonnyola FE enkulu eya AA mu kitundu eky’obusobozi obutono. Ekisinga obukulu, obusobozi bw’okutandika OER ku NiV-LDH-NS (1.73 VRHE) bulwawo okusinga obwo ku Ni(OH)2-NS (1.65 VRHE), ekikwatagana ne FE enkulu eya AA ne FE entono eya O2 ku NiV-LDH-NS ku busobozi obusingako obulungi (Figure 2c).
Okwongera okutegeera okutumbula ekikolwa ky’okukyusa V, twekenneenya OER ne COR reaction kinetics ku Ni(OH)2-NS ne NiV-LDH-NS nga tupima Tafel slopes zaabwe. Kinajjukirwa nti density eriwo kati mu kitundu kya Tafel eva ku oxidation ya Ni2+ okudda mu Ni3+ mu kiseera ky’okugezesa LSV okuva ku potential entono okudda ku potential eya waggulu. Okukendeeza ku bikolwa bya Ni2 + oxidation ku COR Tafel slope okupima, twasooka oxidized catalyst ku 1.8 VRHE okumala edakiika 10 n’oluvannyuma okukola LSV okugezesebwa mu reverse scan mode, kwe kugamba, okuva ku high potential okutuuka ku low potential (Supplementary Fig. 20). Enkokola ya LSV eyasooka yatereezebwa n’okuliyirira kwa iR 100% okusobola okufuna omusenyu gwa Tafel. Mu butabeerawo cyclohexanone, Tafel slope ya NiV-LDH-NS (41.6 mV dec−1) yali wansi okusinga eya Ni(OH)2-NS (65.5 mV dec−1), ekiraga nti OER kinetics yali esobola okunywezebwa V modification (Supplementary Fig. 20c). Oluvannyuma lw’okuleeta cyclohexanone, Tafel slope ya NiV-LDH-NS (37.3 mV dec−1) yali wansi okusinga eya Ni(OH)2-NS (127.4 mV dec−1), ekiraga nti V okukyusa yalina kinetic effect esinga okweyoleka ku COR bw’ogeraageranya ne OER (Supplementary Fig. 20d). Ebivudde mu kunoonyereza kuno biraga nti wadde ng’enkyukakyuka ya V etumbula OER okutuuka ku ddaala eritali limu, eyanguya nnyo entambula ya COR, ekivaamu okweyongera mu FE ya AA.
Okusobola okutegeera okutumbula ekikolwa ky’okukyusa V waggulu ku nkola ya FE ne AA, essira twaliteeka ku kunoonyereza ku nkola. Lipoota ezimu ezaaliwo emabega ziraga nti okukyusakyusa kwa heteroatomu kuyinza okukendeeza ku buziba bw’ebirungo ebiziyiza (crystallinity) n’okwongera ku kitundu ky’okungulu (EAS), bwe kityo ne kyongera ku muwendo gw’ebifo ebikola era bwe kityo ne kirongoosa emirimu gy’ekirungo (catalytic activity)36,37. Okunoonyereza ku kino ekisoboka, twakola ebipimo bya ECSA nga tetunnaba na oluvannyuma lw’okukola electrochemical activation, era ebivuddemu biraga nti ECSA ya Ni (OH) 2-NS ne NiV-LDH-NS zaali zigeraageranyizibwa (Supplementary Fig. 21), nga tobaliddeemu enkola ya active site density oluvannyuma lwa V modification ku catalytic enhancement.
Okusinziira ku kumanya okukkirizibwa okutwalira awamu, mu Ni(OH)2-catalyzed electrooxidation of alcohols oba nucleophilic substrates endala, Ni(OH)2 esooka kufiirwa obusannyalazo ne pulotoni n’oluvannyuma n’ekendeezebwa okutuuka ku NiOOH okuyita mu mitendera gy’obusannyalazo ku potential anodic ezimu38,39,40,41. NiOOH ekoleddwa olwo ekola nga ekika kya COR ekikola ddala okuggya haidrojeni ne obusannyalazo okuva mu kitundu kya nucleophilic substrate okuyita mu mitendera gya kemiko okukola ekintu ekifuuse oxidized20,41. Naye, gye buvuddeko kyategeezebwa nti wadde ng’okukendeeza ku NiOOH kuyinza okukola ng’omutendera ogusalawo omutindo (RDS) ogw’okufuula omwenge ogw’amasannyalaze ku Ni(OH)2, nga bwe kyalagirwa mu biwandiiko ebisembyeyo, okufuuka okw’omukka (oxidation) kw’omwenge gwa Ni3+ kuyinza okuba enkola eyeetongodde okuyita mu kutambuza obusannyalazo obutali bwa redox okuyita mu nkulungo ezitali za Redox eza Ni3+41,42. Nga tuluŋŋamizibwa okunoonyereza okw’enkola okwaloopebwa mu biwandiiko bye bimu, twakozesa dimethylglyoxime disodium salt octahydrate (C4H6N2Na2O2 8H2O) nga molekyu y’okunoonyereza okukwata mu kifo ekitondebwawo kyonna ekya Ni2+ ekiva mu kukendeera kwa Ni3+ mu kiseera kya COR (Supplementary Fig. 22 and Supplementary Note 3). Ebivuddemu biraga okutondebwa kwa Ni2+, nga bikakasa nti okukendeeza kw’eddagala lya NiOOH n’okufuuka kw’amasannyalaze kwa Ni(OH)2 kwaliwo mu kiseera kye kimu mu nkola ya COR. N’olwekyo, omulimu gw’okutabula guyinza okwesigama ennyo ku kinetics y’okukendeeza Ni(OH)2 okutuuka ku NiOOH. Okusinziira ku nkola eno, twaddako okunoonyereza oba okukyusa V kwandiyanguyiza okukendeeza kwa Ni(OH)2 era bwe kityo ne kitereeza COR.
Twasooka kukozesa bukodyo bwa Raman mu kifo okulaga nti NiOOH ye mutendera ogukola ogwa COR ku Ni(OH)2-NS ne NiV-LDH-NS nga twetegereza okutondebwa kwa NiOOH ku busobozi obulungi n’okukozesebwa kwayo okuddirira oluvannyuma lw’okuleeta cyclohexanone, nga tugoberera enkola eyogeddwako waggulu eya “electrochemical-chemical” (Ekifaananyi 3a). Ekirala, okukola kwa NiV-LDH-NS eyazimbibwa obuggya kwasukka okwa Ni(OH)2-NS, nga bwe kiragibwa okubula okw’amangu okw’akabonero ka Ni3+–O Raman. Awo twalaga nti NiV-LDH-NS yalaga obusobozi obutono obulungi obw’okutondebwawo kwa NiOOH bw’ogeraageranya ne Ni(OH)2-NS mu kubeerawo oba obutabaawo kwa cyclohexanone (Figure 3b, c and Supplementary Fig. 4c, d). Ekikulu, omulimu gwa OER ogw’oku ntikko ogwa NiV-LDH-NS guvaamu ebiwujjo ebisingawo okunywerera ku lenzi y’omu maaso ey’ekigendererwa ky’okupima Raman, ekireetera entikko ya Raman ku 1.55 VRHE okubula (Supplementary Fig. 4d). Okusinziira ku bivudde mu DEMS (Supplementary Fig. 18), density ya current ku potentials entono (VRHE < 1.58 ku Ni(OH)2-NS ne VRHE < 1.53 ku NiV-LDH-NS) okusinga eva ku kuddamu okuzimba Ni2+ ions okusinga OER nga tewali cyclohexanone. Bwe kityo, entikko y’okwokya (oxidation peak) ya Ni2+ mu LSV curve ya maanyi okusinga eya NiV-LDH-NS, ekiraga nti enkyukakyuka ya V ewa NiV-LDH-NS obusobozi obw’okuddamu okukola (laba Supplementary Fig. 19 for the detailed analysis).
a In situ Raman spectra za Ni(OH)2-NS (ku kkono) ne NiV-LDH-NS (ku ddyo) wansi w’embeera za OCP oluvannyuma lw’okusooka okufuuka omukka ku 1.5 VRHE mu 0.5 M KOH ne 0.4 M cyclohexanone okumala s 60. b Situ Raman spectra za Ni(OH)2-NS ne c NiV-LDH-NS mu 0.5 M KOH + 0.4 M cyclohexanone ku potential ez’enjawulo. d Situ XANES spectra za Ni(OH)2-NS ne NiV-LDH-NS ku Ni K-edge mu 0.5 M KOH ne e 0.5 M KOH ne 0.4 M cyclohexanone. Ekitundu ekiyingiziddwa kiraga ekitundu kya spektral ekikuziddwa wakati wa 8342 ne 8446 eV. f Embeera za valensi za Ni mu Ni(OH)2-NS ne NiV-LDH-NS ku potential ez’enjawulo. g In situ Ni EXAFS spectra za NiV-LDH-NS nga tebannaba na oluvannyuma lw’okuyingiza cyclohexanone ku potentials ez’enjawulo. h Ebikozesebwa mu ndowooza ya Ni(OH)2-NS ne NiV-LDH-NS. Waggulu: Ku Ni(OH)2-NS, okuddamu okukola mpola okuva ku Ni(OH)2-NS okudda ku NiOOH kukola nga RDS, ate cyclohexanone ekendeeza ku bika bya Ni ebya valenti ennene okuyita mu mitendera gya kemiko okukuuma embeera ya Ni eya valenti entono okukola AA. Wansi: Ku NiV-LDH-NS, omutendera gw’okuddaabiriza gukwanguyibwa okukyusa V, ekivaamu okukyusa RDS okuva ku mutendera gw’okuddamu okukola okudda ku mutendera gw’eddagala. i Amasoboza ag’obwereere aga Gibbs gakyuka ku kuddamu okuzimba Ni(OH)2-NS ne NiV-LDH-NS. Data embisi eya aj ne i eweebwa mu fayiro ya data embisi.
Okunoonyereza ku nkulaakulana y’ensengekera za atomu n’obusannyalazo mu kiseera ky’okukendeeza ku kiziyiza, twakola okugezesa mu kifo (in situ X-ray absorption spectroscopy) (XAS), ekyawa ekintu eky’amaanyi okunoonyereza ku nkyukakyuka y’ebika bya Ni mu mitendera esatu egy’omuddiring’anwa: OER, okukuba empiso ya cyclohexanone, ne COR ku potential ya open circuit (OCP). Ekifaananyi kiraga ebifaananyi bya K-edge XANES ebya Ni ebirina obusobozi obweyongera nga tebannaba kufuyira cyclohexanone n’oluvannyuma lw’okukuba (Ekifaananyi 3d, e). Ku potential y’emu, amasoboza ag’empenda z’okunyiga aga NiV-LDH-NS gasinga nnyo amalungi okusinga aga Ni(OH)2-NS (Ekifaananyi 3d, e, inset). Average valence ya Ni wansi wa buli mbeera yabalirirwa okusinziira ku linear combined fit ya XANES spectra n’okudda emabega kw’enkyukakyuka y’amasoboza ag’okunyiga Ni K-edge (Figure 3f), nga reference spectrum eggiddwa mu biwandiiko ebifulumiziddwa (Supplementary Fig. 23)43.
Mu mutendera ogusooka (nga tebannaba kuleeta cyclohexanone, ekwatagana n’enkola ya OER; Ekifaananyi 3f, ku kkono), ku potential ya catalyst etali ya kuddamu kuzimbibwa (<1.3 VRHE), embeera ya valence ya Ni mu NiV-LDH-NS (+1.83) eri wansi katono okusinga eya Ni(OH)2-NS (+1.97), ekiyinza okuva ku kukyusa obusannyalazo okuva ku V okudda mu Ni, nga kikwatagana n’ebyava mu XPS ebyogeddwako waggulu (Ekifaananyi 2f). Bwe kisukka ekifo ekikendeeza (1.5 VRHE), embeera ya valensi ya Ni mu NiV-LDH-NS (+3.28) eraga okweyongera okweyoleka ennyo bw’ogeraageranya n’eya Ni(OH)2-NS (+2.49). Ku potential eya waggulu (1.8 VRHE), embeera ya valensi y’obutundutundu bwa Ni obufunibwa ku NiV-LDH-NS (+3.64) eri waggulu okusinga eya Ni(OH)2-NS (+3.47). Okusinziira ku lipoota ezaakafuluma, enkola eno ekwatagana n’okutondebwa kw’ebika bya Ni4+ ebirina valenti enkulu mu nsengekera ya Ni3+xOOH1-x (Ni3+x kika kya Ni3+ ne Ni4+ ekitabuddwa), ekyalaga emabegako nti omulimu gw’okutabula ogw’amaanyi mu kuggya amazzi mu mwenge38,39,44. N’olwekyo, omulimu ogw’oku ntikko ogwa NiV-LDH-NS mu COR guyinza okuba nga guva ku kukendeeza okw’amaanyi okukola ebika bya Ni ebikola mu ngeri ey’ekirungo ekinene (catalytically active high-valent Ni species).
Mu mutendera ogwokubiri (okuyingiza cyclohexanone oluvannyuma lw’okuggulawo empeta, ekifaananyi 3f), embeera ya valence ya Ni ku catalysts zombi yakendeera nnyo, ekikwatagana n’enkola y’okukendeeza Ni3+xOOH1-x nga cyclohexanone, ekikwatagana n’ebyava mu in situ Raman spectroscopy (Ekifaananyi 3a), era embeera ya valence ya Ni kumpi yadda mu mbeera eyasooka (omutendera ogusooka ku potensiya entono), ekiraga okukyusakyusa enkola ya redox eya Ni okutuuka ku Ni3+xOOH1-x.
Mu mutendera ogwokusatu (enkola ya COR) ku potensiya za COR (1.5 ne 1.8 VRHE; Ekifaananyi 3f, ku ddyo), embeera ya valensi ya Ni mu Ni(OH)2-NS yeeyongera katono (+2.16 ne +2.40), nga kino kiri wansi nnyo okusinga ku potential y’emu mu mutendera ogusooka (+2.49 ne +3.47). Ebivuddemu bino biraga nti oluvannyuma lw’okukuba empiso ya cyclohexanone, COR ekoma mu kinetically olw’okukyusakyusa empola kwa Ni2+ okutuuka ku Ni3+x (kwe kugamba, okuzimba obuggya Ni) okusinga omutendera gw’eddagala wakati wa NiOOH ne cyclohexanone ku Ni(OH)2-NS, ekireka Ni mu mbeera ya valensi entono. Bwe tutyo, tumaliriza nti okuzimba obuggya Ni kuyinza okukola nga RDS mu nkola ya COR ku Ni(OH)2-NS. Okwawukana ku ekyo, NiV-LDH-NS yakuuma valence enkulu ennyo ey’ebika bya Ni (>3) mu nkola ya COR, era valence yakendeera kitono nnyo (nga wansi wa 0.2) bw’ogeraageranya n’omutendera ogusooka ku potential y’emu (1.65 ne 1.8 VRHE), ekiraga nti V modification kinetically promoted the oxidation of Ni2+ to Ni3+x, making the Ni reduction process faster okusinga omutendera gw’eddagala ogw’okukendeeza ku cyclohexanone. Ebivudde mu nsengekera ennungi ey’okunyiga X-ray eyagaziyiziddwa (EXAFS) nabyo byalaga enkyukakyuka enzijuvu ey’enkolagana ya Ni–O (okuva ku 1.6 okutuuka ku 1.4 Å) ne Ni–Ni(V) (okuva ku 2.8 okutuuka ku 2.4 Å) nga waliwo cyclohexanone. Kino kikwatagana n’okuddamu okuzimba ekitundu kya Ni(OH)2 okutuuka ku kitundu kya NiOOH n’okukendeeza ku mutendera gwa NiOOH mu kemiko nga bakozesa cyclohexanone (Fig. 3g). Wabula, cyclohexanone yalemesa nnyo okukendeeza kinetics ya Ni(OH)2-NS (laba Supplementary Note 4 ne Supplementary Fig. 24 okumanya ebisingawo).
Okutwaliza awamu, ku Ni(OH)2-NS (Fig. 3h, waggulu), omutendera gw’okukendeeza mpola okuva ku mutendera gwa Ni(OH)2 okutuuka ku mutendera gwa NiOOH guyinza okukola nga RDS y’enkola ya COR okutwalira awamu okusinga omutendera gw’eddagala ogw’okutondebwawo kwa AA okuva mu cyclohexanone mu kiseera ky’okukendeeza eddagala lya NiOOH. Ku NiV-LDH-NS (Fig. 3h, wansi), enkyukakyuka ya V eyongera ku kinetics y’okwokya (oxidation kinetics) ya Ni2+ okutuuka ku Ni3+x, bwe kityo ne kyanguya okutondebwa kwa NiVOOH (okusinga okukozesa okukendeeza ku kemiko), ekikyusa RDS okudda ku ddaala ly’eddagala. Okutegeera okuzimba obuggya kwa Ni okuleetebwa enkyukakyuka ya V, twakola okubalirira okulala okw’enzikiriziganya. Nga bwe kiragibwa mu kifaananyi 3h, twakoppa enkola y’okuddamu okuzimba Ni(OH)2-NS ne NiV-LDH-NS. Ebibinja bya lattice hydroxyl ku Ni(OH)2-NS ne NiV-LDH-NS biggyibwako pulotoni nga tuggyamu OH- mu electrolyte okukola lattice oxygen etaliimu busannyalazo. Ensengekera z’eddagala ezikwatagana ze zino wammanga:
Enkyukakyuka y’amasoboza ag’obwereere aga Gibbs ag’okuzimba obuggya yabalirirwa (Ekifaananyi 3i), era NiV-LDH-NS (0.81 eV) yalaga enkyukakyuka y’amasoboza ag’obwereere aga Gibbs entono nnyo okusinga Ni(OH)2-NS (1.66 eV), ekiraga nti enkyukakyuka ya V yakendeeza ku vvulovumenti eyeetaagisa okuzimba obuggya Ni. Tukkiriza nti okutumbula okuzimba okuddamu kuyinza okukendeeza ku kiziyiza ky’amasoboza ga COR yonna (laba okunoonyereza ku nkola y’ensengekera wansi okumanya ebisingawo), bwe kityo ne kyanguya enzirukanya ku densite za kasasiro ezisingako.
Okwekenenya waggulu kulaga nti enkyukakyuka ya V ereeta okuddamu okusengeka kwa phase okw’amangu okwa Ni(OH)2, bwe kityo ne kyongera ku sipiidi y’ensengekera era, mu ngeri endala, density ya kasasiro ya COR. Naye ebifo bya Ni3+x nabyo bisobola okutumbula omulimu gwa OER. Okuva ku kiwujjo kya LSV ekitaliimu cyclohexanone, kyeyoleka bulungi nti density ya NiV-LDH-NS eriwo kati eri waggulu okusinga eya Ni(OH)2-NS (Supplementary Fig. 19), ekivaako ensengekera za COR ne OER okukola ensengekera z’okuvuganya. N’olwekyo, FE eya waggulu ennyo eya AA okusinga eya NiV-LDH-NS teyinza kunnyonnyolwa mu bujjuvu n’enkyukakyuka ya V etumbula okuddamu okusengeka phase.
Kikkirizibwa okutwalira awamu nti mu mikutu gya alkaline, ensengekera z’obusannyalazo (electrooxidation reactions) eza nucleophilic substrates zitera okugoberera enkola ya Langmuir–Hinshelwood (LH). Okusingira ddala, substrate ne OH− aniyoni zivuganya mu kuyungibwa ku ngulu w’ekirungo ekiziyiza, era OH− enywezeddwa efuuka oxidized okutuuka ku bibinja bya hydroxyl ebikola (OH*), ebikola nga electrophiles for the oxidation of nucleophiles, enkola eyalagibwa emabegako mu data y’okugezesa ne/oba okubalirira okw’enzikiriziganya45,46,47. Bwe kityo, ekisengejjo ky’ebirungo ebikola n’omugerageranyo gwabyo (organic substrate ne OH−) bisobola okufuga okubikka kw’ebirungo ebikola ku ngulu w’ekirungo ekiziyiza, bwe kityo ne kikosa FE n’amakungula g’ekintu ekigendererwa14,48,49,50. Mu mbeera yaffe, tuteebereza nti okubikka kungulu kwa cyclohexanone okungi mu NiV-LDH-NS kusinga kwagala nkola ya COR, ate mu ngeri endala, okubikka kungulu kwa cyclohexanone okutono mu Ni (OH) 2-NS kusinga kwagala nkola ya OER.
Okugezesa endowooza eyo waggulu, twasooka kukola emitendera ebiri egy’okugezesa okukwatagana n’obungi bw’ebirungo ebikola (C, cyclohexanone, ne COH−). Okugezesa okusooka kwakolebwa n’okusengejja amasannyalaze ku potensiya etakyukakyuka (1.8 VRHE) ku Ni(OH)2-NS ne NiV-LDH-NS catalysts nga zirina cyclohexanone C ez’enjawulo (0.05 ~ 0.45 M) n’ebirimu COH− ebinywevu (0.5 M). Olwo, ebivaamu bya FE ne AA byabalirirwa. Ku NiV-LDH-NS catalyst, enkolagana wakati w’amakungula ga AA ne cyclohexanone C yalaga curve eya bulijjo “ekika ky’olusozi” mu mbeera ya LH (Fig. 4a), ekiraga nti okubikka kwa cyclohexanone okungi kuvuganya n’okusikiriza kwa OH−. So nga ku Ni(OH)2-NS, amakungula ga AA geeyongera mu ngeri ya monotonically nga C ya cyclohexanone yeeyongera okuva ku 0.05 okutuuka ku 0.45 M, ekiraga nti wadde ng’obungi bwa cyclohexanone bwali bungi (0.45 M), okubikka kwayo kungulu kwali kukyali wansi nnyo. Okugatta ku ekyo, n’okweyongera kwa COH− okutuuka ku 1.5 M, “ekika ky’olusozi” curve yalabibwa ku Ni (OH) 2-NS okusinziira ku C ya cyclohexanone, era inflection point y’omulimu yalwawo bw’ogeraageranya ne NiV-LDH-NS, ekyongera okukakasa okuyungibwa okunafu okwa cyclohexanone ku Ni(OH)2-NS (Supplementary Fig. 25a and Note 5). Okugatta ku ekyo, FE ya AA ku NiV-LDH-NS yali ewulikika nnyo ku C-cyclohexanone era yeeyongera mangu okutuuka ku bitundu ebisukka mu 80% nga C-cyclohexanone eyongezeddwa okuva ku 0.05 M okutuuka ku 0.3 M, ekiraga nti cyclohexanone yali nnyangu okugaggawala ku NiV-LDH-NS (Ekifaananyi 4b). Okwawukana ku ekyo, okwongera ku bungi bwa C-cyclohexanone tekyaziyiza nnyo OER ku Ni(OH)2-NS, ekiyinza okuba nga kiva ku butasikiriza bwa cyclohexanone obutamala. Okwawukana ku ekyo, okunoonyereza okulala ku kwesigama kwa COH− ku bulungibwansi bw’okutabula nakyo kyakakasa nti okusikiriza kwa cyclohexanone kwalongoosebwa bw’ogeraageranya ne NiV-LDH-NS, eyinza okugumira COH− eyali waggulu mu nkola ya COR awatali kukendeeza ku FE ya AA (Supplementary Fig. 25b, c and Note 5).
Ebibala bya AA ne EF bya b Ni(OH)2-NS ne NiV-LDH-NS ku cyclohexanone ne C ez’enjawulo mu 0.5 M KOH. c Amasoboza g’okusikiriza aga cyclohexanone ku NiOOH ne NiVOOH. d FE ya AA ku Ni(OH)2-NS ne NiV-LDH-NS mu 0.5 M KOH ne 0.4 M cyclohexanone ku 1.80 VRHE nga tukozesa enkola z’obusobozi obutagenda mu maaso era obutakyukakyuka. Embaawo z’ensobi zikiikirira okukyama okutuufu okw’ebipimo bisatu ebyetongodde nga tukozesa sampuli y’emu era nga biri mu bitundu 10%. e Waggulu: Ku Ni(OH)2-NS, cyclohexanone erimu ekitundu ekitono eky’okungulu C enywezebwa mu ngeri enafu ne cyclohexanone, ekivaamu okuvuganya okw’amaanyi ku OER. Wansi: Ku NiV-LDH-NS, ekitundu ekinene eky’okungulu ekya cyclohexanone C kyeyolekera nga kweyongera okusikiriza kwa cyclohexanone, ekivaamu okunyigirizibwa kwa OER. Data embisi eya a–d eweebwa mu fayiro ya data embisi.
Okugezesa enhanced adsorption ya cyclohexanone ku NiV-LDH-NS, twakozesa electrochemical coupled quartz crystal microbalance (E-QCM) okulondoola enkyukakyuka mu bungi bw’ebika ebinywezeddwa mu kiseera ekituufu. Ebivuddemu biraga nti obusobozi bw’okusikiriza mu kusooka obwa cyclohexanone ku NiV-LDH-NS bwali bunene emirundi 1.6 okusinga ku Ni(OH)2-NS mu mbeera ya OCP, era enjawulo eno mu busobozi bw’okusikiriza yeeyongera okweyongera ng’obusobozi bweyongera okutuuka ku 1.5 VRHE (Supplementary Fig. 26). Okubalirira kwa DFT okwa spin-polarized kwakolebwa okunoonyereza ku nneeyisa y’okusikiriza kwa cyclohexanone ku NiOOH ne NiVOOH (Ekifaananyi 4c). Cyclohexanone enywera ku Ni-center ku NiOOH n’amasoboza ag’okusikiriza (Eads) aga -0.57 eV, ate cyclohexanone esobola okunyiga ku Ni-center oba V-center ku NiVOOH, nga V-center egaba Eads eya wansi ennyo (-0.69 eV), ekwatagana n’okusikiriza okw’amaanyi okwalabiddwa okwa cyclohexanone ku NiVOOH.
Okwongera okukakasa nti okunywezebwa okw’okusikiriza kwa cyclohexanone kuyinza okutumbula okutondebwa kwa AA n’okuziyiza OER, twakozesa enkola y’obusobozi obutagenda mu maaso okugaggawaza cyclohexanone ku ngulu w’ekirungo ekiziyiza (ku Ni (OH) 2-NS ne NiV-LDH-NS), ekyaluŋŋamizibwa lipoota ezaaliwo emabega. 51, 52 Okusingira ddala, twakozesa potential ya 1.8 VRHE ku COR, oluvannyuma ne tugikyusa mu mbeera ya OCP, n’oluvannyuma ne tugikyusa ne tudda ku 1.8 VRHE. Mu mbeera eno, cyclohexanone esobola okukuŋŋaanyizibwa ku ngulu w’ekirungo ekiziyiza mu mbeera ya OCP wakati w’obusannyalazo (laba ekitundu ky’Enkola okumanya enkola enzijuvu). Ebivuddemu biraga nti ku Ni(OH)2-NS ne NiV-LDH-NS, okukozesa discontinuous potential electrolysis kyalongoosa omulimu gwa catalytic bw’ogeraageranya ne constant potential electrolysis (Figure 4d). Ekikulu, Ni(OH)2-NS yalaga okulongoosa okw’amaanyi mu COR (AA FE: okuva ku 51% okutuuka ku 82%) n’okunyigirizibwa kwa OER (O2 FE: okuva ku 27% okutuuka ku 4%) okusinga NiV-LDH-NS, ekyava ku kuba nti okukuŋŋaanyizibwa kwa cyclohexanone kuyinza okulongoosebwa ku kigero ekinene ku catalyst n’obusobozi bw’okusikiriza obunafu (kwe kugamba, Ni(OH)2-NS) nga tuyita mu kusengejja obusobozi bw’amasannyalaze obutasalako.
Okutwaliza awamu, okuziyiza OER ku NiV-LDH-NS kuyinza okuva ku kwongera okusikiriza kwa cyclohexanone (Ekifaananyi 4e). Ku Ni(OH)2-NS (Ekifaananyi 4e, waggulu), okuyungibwa okunafu okwa cyclohexanone kwavaamu okubikka kwa cyclohexanone okutono ennyo n’okubikka kwa OH* okunene ennyo ku ngulu w’ekirungo ekiziyiza. N’olwekyo, ebika bya OH* ebisukkiridde bijja kuleeta okuvuganya okw’amaanyi ku OER era bikendeeze ku FE ya AA. Okwawukana ku ekyo, ku NiV-LDH-NS (Ekifaananyi 4e, wansi), enkyukakyuka ya V yayongera ku busobozi bw’okusikiriza bwa cyclohexanone, bwe kityo n’eyongera ku ngulu C eya cyclohexanone era n’ekozesa obulungi ebika bya OH* ebinywezeddwa ku COR, okutumbula okutondebwa kwa AA n’okuziyiza OER.
Ng’oggyeeko okunoonyereza ku ngeri enkyukakyuka ya V gy’ekwata ku kuddamu okuzimba ebika bya Ni n’okusikiriza kwa cyclohexanone, era twanoonyereza oba V ekyusa ekkubo ly’okutondebwa kwa AA okuva mu COR. Amakubo ga COR ag’enjawulo agawerako gateeseddwa mu biwandiiko, era twekenneenyezza ebisoboka mu nkola yaffe ey’okuddamu (laba Supplementary Fig. 27 ne Supplementary Note 6 okumanya ebisingawo)13,14,26. Okusooka, kigambibwa nti omutendera ogusooka ogw’ekkubo lya COR guyinza okuzingiramu okusooka okufuuka oxidation ya cyclohexanone okukola ekisumuluzo eky’omu makkati 2-hydroxycyclohexanone (2)13,14. Okukakasa enkola eno, twakozesa 5,5-dimethyl-1-pyrrolidine N-oxide (DMPO) okutega ebirungo ebikola eby’omu makkati ebinywezeddwa ku ngulu w’ekirungo ekiziyiza era ne tusoma EPR. Ebivudde mu EPR biraga okubeerawo kwa C-centered radicals (R ) ne hydroxyl radicals (OH ) ku catalysts zombi mu nkola ya COR, ekiraga nti Cα − H dehydrogenation ya cyclohexanone ekola intermediate enolate radical (1), oluvannyuma eyongera okufuuka oxidized ne OH* okukola 2 (Fig. 5a ne Supplementary Fig. 28). Newankubadde nga ebirungo bye bimu eby’omu makkati byazuulibwa ku biziyiza byombi, ekitundu ky’ekitundu ky’akabonero ka R ku NiV-LDH-NS kyali kisinga nnyo ekya Ni(OH)2-NS, ekiyinza okuba nga kiva ku busobozi bw’okusikiriza obweyongedde obwa cyclohexanone (Supplementary Table 3 and Note 7). Twayongera okukozesa 2 ne 1,2-cyclohexanedione (3) nga ebirungo ebitandikira ku electrolysis okugezesa oba V yandikyusizza omutendera gw’okwokya oguddako. Ebivudde mu kusengejja amasannyalaze eby’ebiyinza okubeera wakati (2 ne 3) ku Ni(OH)2-NS ne NiV-LDH-NS byalaga okulonda kw’ebintu okugeraageranya, ekiraga nti enkola ya COR ku Ni(OH)2-NS oba NiV-LDH-NS yagenda mu maaso ng’eyita mu makubo agafaanagana (Ekifaananyi 5b). Ate era, AA ye yali ekintu ekikulu ekivaamu kyokka nga 2 ekozesebwa ng’ekirungo ekikola, ekiraga nti AA yafunibwa okuyita mu nkola ya oxidation obutereevu okuyita mu kukutula Cα − Cβ bond ya 2 okusinga oxidation eyaddirira okutuuka ku 3 ku catalysts zombi, okuva bwe kiri nti okusinga yakyusibwa okufuuka GA nga 3 ekozesebwa nga reactant etandika (Supplementary Figures 29, 30).
Akabonero ka EPR aka NiV-LDH-NS mu 0.5 M KOH + 0.4 M cyclohexanone. b Ebivudde mu kwekenneenya amasannyalaze aga 2-hydroxycyclohexanone (2) ne 1,2-cyclohexanedione (3). Okusengejja amasannyalaze kwakolebwa mu 0.5 M KOH ne 0.1 M 2 oba 3 ku 1.8 VRE okumala essaawa emu. Embaawo z’ensobi zikiikirira okukyama okutuufu okw’ebipimo bibiri ebyetongodde nga tukozesa ekirungo ekiziyiza (catalyst) kye kimu. c Amakubo g’ensengekera agateeseddwa aga COR ku biwujjo ebibiri. d Ekifaananyi ekiraga ekkubo lya COR ku Ni(OH)2-NS (ku kkono) ne d NiV-LDH-NS (ku ddyo). Obusaale obumyufu bulaga emitendera enkyukakyuka ya V gy’etumbula mu nkola ya COR. Data embisi eya a ne b eweebwa mu fayiro ya data embisi.
Okutwaliza awamu, twalaga nti Ni (OH) 2-NS ne NiV-LDH-NS zitabula COR nga ziyita mu kkubo erifaanagana: cyclohexanone enywezebwa ku ngulu w’ekirungo, dehydrogenated era n’efiirwa obusannyalazo okukola 1, oluvannyuma ne bufuuka oxidized ne OH * okukola 2, ne guddirirwa enkyukakyuka ez’emitendera mingi okuvaamu AA (Figure 5c). Wabula, cyclohexanone bwe yakozesebwa nga ekirungo, okuvuganya kwa OER kwalabibwa ku Ni(OH)2-NS yokka, ate nga omuwendo gwa oxygen ogusinga wansi gwakunganyizibwa nga 2 ne 3 zikozesebwa nga ekirungo. Bwe kityo, enjawulo ezitunuuliddwa mu nkola ya katalisiti ziyinza okuba nga ziva ku nkyukakyuka mu kiziyiza ky’amasoboza ga RDS n’obusobozi bw’okusikiriza cyclohexanone obuva ku nkyukakyuka ya V okusinga enkyukakyuka mu kkubo ly’ensengekera. N’olwekyo twekenneenya RDS y’amakubo g’ensengekera ku biziyiza byombi. Ebivudde mu kukebera amaloboozi mu kifo (in situ X-ray acoustic spectroscopy) ebyogeddwako waggulu biraga nti enkyukakyuka ya V ekyusa RDS mu nkola ya COR okuva ku mutendera gw’okuddamu okuzimba okudda ku mutendera gw’eddagala, okukuuma omutendera gwa NiOOH n’ebika bya Ni eby’omuwendo omungi nga tebifudde ku NiV-LDH-NS (Fig. 3f, Supplementary Fig. 24, and Note 4). Twayongera okwekenneenya enkola z’ensengekera ezikiikirirwa density ya kasasiro mu buli kitundu ky’ebitundu eby’enjawulo eby’obusobozi mu kiseera ky’okupima CV (laba Supplementary Fig. 31 ne Note 8 okumanya ebisingawo) era ne tukola H/D kinetic isotope exchange experiments, nga byonna awamu byalaga nti RDS ya COR ku NiV-LDH-NS erimu okukutula Cα − H bond mu mutendera gw’eddagala okusinga okukendeeza omutendera (laba Ekifaananyi eky’okugattako 32 ne Note 8 okumanya ebisingawo).
Okusinziira ku kwekenneenya waggulu, okutwalira awamu ekikolwa ky’okukyusa V kiragibwa mu kifaananyi 5d. Ni(OH)2-NS ne NiV-LDH-NS catalysts ziyita mu surface reconstruction ku high anodic potentials ne catalyze COR nga ziyita mu kkubo erifaanagana. Ku Ni(OH)2-NS (Ekifaananyi 5d, ku kkono), omutendera gw’okuddamu okuzimba ye RDS mu kiseera ky’enkola ya COR; ate ku NiV-LDH-NS (Ekifaananyi 5d, ku ddyo), okukyusa V kwayanguyira nnyo enkola y’okuzimba obuggya era n’ekyusa RDS mu Cα−H dehydrogenation ya cyclohexanone okukola 1. Okugatta ku ekyo, okusikiriza kwa cyclohexanone kwaliwo mu kifo kya V era ne kwongera ku NiV-LDH-NS, ekyayamba mu kunyigiriza OER.
Okulowooza ku nkola ennungi ennyo ey’obusannyalazo eya NiV-LDH-NS nga erina FE enkulu ku bbanga erigazi ery’obusobozi, twakola enteekateeka ya MEA okutuuka ku kukola AA okutambula obutasalako. MEA yakuŋŋaanyizibwa nga tukozesa NiV-LDH-NS nga anode, PtRu/C ey’ettunzi nga cathode53 n’oluwuzi oluwanyisiganya anion (ekika: FAA-3-50) (Ekifaananyi 6a ne Supplementary Fig. 33)54. Okuva vvulovumenti y’obutoffaali bwe yakendeera era nga FE ya AA egeraageranyizibwa ne 0.5 M KOH mu kunoonyereza waggulu, ekirungo kya anolyte kyalongoosebwa okutuuka ku 1 M KOH (Supplementary Fig. 25c). Enkokola za LSV eziwandiikiddwa ziragiddwa mu kifaananyi eky’okugattako 34, ekiraga nti obulungi bwa COR bwa NiV-LDH-NS buli waggulu nnyo okusinga obwa Ni(OH)2-NS. Okulaga obusukkulumu bwa NiV-LDH-NS, constant current electrolysis yakolebwa nga step current density etandikira ku 50 okutuuka ku 500 mA cm−2 era voltage y’obutoffaali ekwatagana n’ewandiikibwa. Ebivuddemu biraga nti NiV-LDH-NS yalaga vvulovumenti y’obutoffaali eya 1.76 V ku density ya kasasiro eya 300 mA cm−2, nga eno yali wansi nga 16% okusinga eya Ni(OH)2-NS (2.09 V), ekiraga nti ekozesa amaanyi gaayo amangi mu kukola AA (Fig. 6b).
Schematic diagram ya bbaatule ekulukuta. b Voltage y’obutoffaali nga tewali kuliyirirwa kwa iR ku Ni(OH)2-NS ne NiV-LDH-NS mu 1 M KOH ne 0.4 M cyclohexanone ku densite za kasasiro ez’enjawulo. c Amakungula ga AA ne FE ku Ni(OH)2-NS ne NiV-LDH-NS ku densite za kasasiro ez’enjawulo. Embaawo z’ensobi zikiikirira okukyama okutuufu okw’ebipimo bibiri ebyetongodde nga tukozesa ekirungo ekiziyiza (catalyst) kye kimu. d Okugerageranya omulimu gwa catalytic ogw’omulimu gwaffe n’enkola endala eza bbaatule ezikulukuta ezaaloopebwa14,17,19. Ebipimo by’ensengekera n’engeri z’ensengekera biwandiikiddwa mu bujjuvu mu kipande eky’okugattako 2. e Voltage y’obutoffaali ne FE ya AA ku NiV-LDH-NS ku 200 ne 300 mA cm−2 mu kugezesebwa okw’ekiseera ekiwanvu, okusinziira ku. Data embisi eya be eweebwa nga fayiro ya data embisi.
Mu kiseera kino, nga bwe kiragibwa mu kifaananyi 6c, NiV-LDH-NS okusinga yakuuma FE ennungi (83% okutuuka ku 61%) ku density ya kasasiro eya waggulu (200 ku 500 mA cm-2), bwe kityo n’elongoosa ebibala bya AA (1031 okutuuka ku 1900 μmol cm-2 h-1). Mu kiseera kino, 0.8% zokka eza adipic acid aniions ze zaalabibwa mu kisenge kya cathode oluvannyuma lw’okusengejja amasannyalaze, ekiraga nti enkyukakyuka ya cyclohexanone teyali nnene mu mbeera yaffe (Supplementary Fig. 35). Okwawukana ku ekyo, n’omutindo gwe gumu ogw’okweyongera kwa density ya kasasiro, FE ya AA ku Ni(OH)2-NS yakendeera okuva ku 61% okutuuka ku 34%, ekyakaluubiriza okulongoosa ebibala bya AA (762 okutuuka ku 1050 μmol cm-2 h-1). Okusingira ddala, omulimu gwa AA gwakendeera wadde katono olw’okuvuganya okw’amaanyi okuva mu OER, era bwe kityo FE ya AA yakendeera nnyo nga density ya current yeeyongera (okuva ku 200 okutuuka ku 250 mA cm−2, Supplementary Fig. 5). Okusinziira ku kye tumanyi, ebivudde mu kutabula nga tukozesa MEA n’ebirungo ebiziyiza NiV-LDH-NS bisukka nnyo omulimu gw’ebirungo ebikulukuta ebyategeezebwa emabegako ebirina ebirungo ebikola Ni-based catalysts (Supplementary Table 2). Ate era, nga bwe kiragibwa mu kifaananyi 6d, NiV-LDH-NS yalaga enkizo ennene mu nsonga za density ya kasasiro, voltage y’obutoffaali, ne FE ya AA bw’ogeraageranya n’ekirungo ekisinga okukola obulungi Co-based catalyst, kwe kugamba, graphene-supported Co3O4 (Co3O4/GDY)17. Okugatta ku ekyo, twekenneenya enkozesa y’amasoboza mu kukola AA ne tulaga nti enkozesa ya AA yali ntono nnyo, 2.4 W h gAA-1 yokka ku density ya current eya 300 mA cm-2 ne voltage y’obutoffaali eya 1.76 V (okubalirira mu bujjuvu kuweereddwa mu Supplementary Note 1). Bw’ogeraageranya n’ekivaamu ekisinga obulungi ekya 4.1 W h gAA-1 ku Co3O4/GDY ekyaloopebwa emabegako, amaanyi agakozesebwa mu kukola AA mu mulimu gwaffe gakendeera ebitundu 42% era ebivaamu ne byeyongera emirundi 4 (1536 vs. 319 μmol cm-2 h-1)17.
Obunywevu bw’ekirungo kya NiV-LDH-NS ekiziyiza okukola AA okumala ebbanga eddene mu MEA bwakeberebwa ku densities eziriwo kati eza 200 ne 300 mA cm-2, okusinziira ku (Figure 6e). Okuva OH− bwekozesebwa mangu ku densite za kasasiro ezisingako, omuwendo gw’okuzza obuggya obusannyalazo ku 300 mA cm-2 guli waggulu okusinga ogwo ku 200 mA cm-2 (laba akatundu akatono “Ebipimo by’amasannyalaze” okumanya ebisingawo). Ku density ya current eya 200 mA cm-2, average COR efficiency yali 93% mu 6 h ezisooka, olwo n’ekendeera katono okutuuka ku 81% oluvannyuma lwa 60 h, ate cell voltage yeeyongera katono ne 7% (okuva ku 1.62 V okutuuka ku 1.73 V), ekiraga okutebenkera okulungi. Nga density ya current yeeyongera okutuuka ku 300 mA cm−2, AA efficiency yasigala kumpi nga tekyuse (yakendeera okuva ku 85% okutuuka ku 72%), naye cell voltage yeeyongera nnyo (okuva ku 1.71 okutuuka ku 2.09 V, ekikwatagana ne 22%) mu kiseera ky’okugezesa 46-h (Figure 6e). Tuteebereza nti ensonga enkulu evuddeko okuvunda kw’omulimu kwe kukulukuta kw’oluwuzi oluwanyisiganya anion (AEM) olwa cyclohexanone, ekivaako okweyongera mu buziyiza bw’obutoffaali ne vvulovumenti y’obutoffaali bw’amasannyalaze (Supplementary Fig. 36), nga buwerekerwako okukulukuta okutono okw’obusannyalazo okuva mu anode okutuuka ku katodi, ekivaamu okukendeera kw’obunene bwa anolyte n’obwetaavu bw’okuyimiriza okusengejja amasannyalaze. Okugatta ku ekyo, okukendeera kwa FE ya AA nakyo kiyinza okuba nga kiva ku kukulukuta kw’ebirungo ebiziyiza (catalysts), ekisinga okwagala okuggulawo ekifuumuuka kya Ni eri OER. Okulaga enkosa ya AEM efuuse ekivundu ku kuvunda kw’obutebenkevu ku 300 mA cm−2, twagikyusa ne tussaamu AEM empya oluvannyuma lw’essaawa 46 ez’okusaanuusa amasannyalaze. Nga bwe kyali kisuubirwa, obulungi bw’okutabula bwazzibwawo bulungi, nga vvulovumenti y’obutoffaali ekendedde nnyo okutuuka ku muwendo ogwasooka (okuva ku 2.09 okutuuka ku 1.71 V) n’oluvannyuma n’eyongera katono mu ssaawa 12 eziddako ez’okusengejja amasannyalaze (okuva ku 1.71 okutuuka ku 1.79 V, okweyongera kwa 5%; Ekifaananyi 6e).
Okutwaliza awamu, twasobola okutuuka ku ssaawa 60 ez’obutebenkevu bw’okufulumya AA obutasalako ku density ya kasasiro eya 200 mA cm−2, ekiraga nti FE ne vvulovumenti y’obutoffaali bwa AA bikuumibwa bulungi. Twagezaako era density ya current esingako eya 300 mA cm−2 era ne tutuuka ku stability okutwalira awamu eya 58 h, nga tukyusa AEM ne tussaamu empya oluvannyuma lwa 46 h. Okunoonyereza waggulu kulaga obutebenkevu bw’ekirungo ekiziyiza (catalyst) era kulaga bulungi obwetaavu bw’okukulaakulanya AEM ez’amaanyi amangi mu biseera eby’omu maaso okulongoosa obutebenkevu obw’ekiseera ekiwanvu obwa MEA olw’okufulumya AA obutasalako ku densities z’amasannyalaze ezisinga obulungi mu makolero.
Okusinziira ku nkola ya MEA yaffe, twateesa enkola enzijuvu ey’okufulumya AA omuli okuliisa substrate, electrolysis, neutralization, n’okwawula units (Supplementary Fig. 37). Okwekenenya emirimu okusooka kwakolebwa okwekenneenya obusobozi bw’ebyenfuna bw’enkola eno nga tukozesa enkola y’okufulumya kabokisi ya alkaline electrolyte electrocatalytic carboxylate55. Mu mbeera eno, ebisale mulimu kapito, emirimu, n’ebikozesebwa (Fig. 7a ne Supplementary Fig. 38), era enyingiza eva mu kukola AA ne H2. Ebivudde mu TEA biraga nti mu mbeera yaffe ey’emirimu (current density 300 mA cm-2, cell voltage 1.76 V, FE 82%), omugatte gw’ensimbi n’enyingiza biri US$2429 ne US$2564, okusinziira ku magoba amatuufu aga US$135 buli ttani ya AA ekoleddwa (laba Supplementary Note 9 okumanya ebisingawo).
a Omuwendo gwonna ogw’enkola ya AA electrochemical wansi w’embeera ya base case nga FE ya 82%, density ya current ya 300 mA cm−2, ne cell voltage ya 1.76 V. Okwekenenya sensitivity costs essatu eri b FE ne c current density. Mu kwekenneenya obuwulize, ebipimo byokka ebyasomesebwa bye byakyusibwakyusibwa ate ebipimo ebirala ne bikuumibwa nga tebikyukakyuka okusinziira ku nkola ya TEA. d Ebikosa FE ez’enjawulo ne density ya kasasiro ku magoba ga AA electrosynthesis n’amagoba nga tukozesa Ni(OH)2-NS ne NiV-LDH-NS, nga tufudde nti vvulovumenti y’obutoffaali ekuumibwa nga tekyukakyuka ku 1.76 V. Data eziyingizibwa ku a–d ziweebwa mu fayiro ya data embisi.
Okusinziira ku nsonga eno, twayongera okunoonyereza ku ngeri FE ne density ya current gye bikwata ku magoba ga AA electrosynthesis. Twakizuula nti amagoba gakwata nnyo ku FE ya AA, okuva okukendeera kwa FE bwe kuleeta okweyongera okw’amaanyi mu nsaasaanya y’emirimu, bwe kityo ne kyongera nnyo ku nsaasaanya okutwalira awamu (Ekifaananyi 7b). Ku bikwata ku density ya current, density ya current esingako (>200 mA cm-2) eyamba okukendeeza ku nsaasaanya ya kapito n’omuwendo gw’okuzimba ekyuma, okusinga nga kikendeeza ku kitundu ky’obutoffaali bw’amasannyalaze, bwe kityo ne kiyamba okwongera ku magoba (Figure 7c). Bw’ogeraageranya ne density eriwo kati, FE erina kinene ky’ekola ku magoba. Nga tulaga enkosa ya FE ne density ya kasasiro ku magoba, tulaba bulungi obukulu bw’okutuuka ku FE eya waggulu (>60%) ku density za current ezikwatagana mu makolero (>200 mA cm-2) okukakasa amagoba. Olw’omuwendo gwa FE ogw’amaanyi ogwa AA, enkola y’ensengekera ne NiV-LDH-NS nga ekiziyiza esigala nga nnungi mu bbanga lya 100–500 mA cm−2 (ennyiriri za pentagram; Ekifaananyi 7d). Naye ku Ni(OH)2-NS, okukendeeza ku FE ku density ya current enkulu (>200 mA cm−2) kyavaako ebivaamu ebitali birungi (circles; Ekifaananyi 7d), ekiraga obukulu bwa catalysts ezirina FE enkulu ku density ya current enkulu.
Ng’oggyeeko obukulu bw’ebiziyiza mu kukendeeza ku nsaasaanya ya kapito n’emirimu, okwekenneenya kwaffe okwa TEA kulaga nti amagoba gayinza okwongera okulongoosebwa mu ngeri bbiri. Ekisooka kwe kutunda wamu ekirungo kya potassium sulfate (K2SO4) ku katale ng’ekiva mu kitundu ekiziyiza okuzimba, naye nga kiyinza okuvaamu doola za Amerika 828/t AA-1 (Supplementary Note 9). Ekyokubiri kwe kulongoosa tekinologiya w’okulongoosa, omuli okuddamu okukola ebintu oba okukola tekinologiya ow’okwawula AA asinga okukekkereza ssente (ebirala mu yuniti z’okuziyiza n’okwawula). Enkola ya acid-base neutralization ekozesebwa mu kiseera kino esobola okuvaamu ssente nnyingi ez’ebintu (ezisinga obunene ku 85.3%), nga ku zino 94% ziva ku cyclohexanone ne KOH ($2069/t AA-1; Ekifaananyi 7a), naye nga bwe kyayogeddwa waggulu, enkola eno okutwalira awamu ekyakola amagoba. Tuteesa nti ssente z’ebintu ziyinza okwongera okukendeezebwa n’enkola ez’omulembe ennyo ez’okuzzaawo KOH ne cyclohexanone ezitakola, gamba nga electrodialysis okusobola okuzzaawo KOH14 mu bujjuvu (omuwendo ogubalirirwamu ogwa US$1073/t AA-1 okuyita mu electrodialysis; Supplementary Note 9).
Mu bufunze, twatuuka ku bulungibwansi obw’amaanyi obw’obusannyalazo bwa atomu ya aluminiyamu ku density ya kasasiro eya waggulu nga tuyingiza V mu Ni(OH)2 nanosheets. Wansi w’obusobozi obugazi obwa 1.5–1.9 VRHE ne density ya kasasiro eya waggulu eya 170 mA cm−2, AA FE ku NiV-LDH-NS yatuuka ku 83–88%, ate OER yanyigirizibwa bulungi okutuuka ku 3%. Enkyukakyuka ya V yatumbula okukendeeza kwa Ni2+ okutuuka ku Ni3+x era n’eyongera ku kuyungibwa kwa cyclohexanone. Ebiwandiiko eby’okugezesa n’eby’enzikiriziganya biraga nti okuzimba obuggya okusikirizibwa kwongera ku density ya kasasiro ku cyclohexanone oxidation era ne kukyusa RDS ya COR okuva mu kuddamu okuzimba okudda ku dehydrogenation erimu Cα − H scission, ate nga okunywezebwa okusikiriza kwa cyclohexanone kunyigiriza OER. Enkulaakulana ya MEA yatuuka ku kukola AA okutambula obutasalako ku density y’amasannyalaze g’amakolero eya 300 mA cm−2, record AA efficiency ya 82%, n’obulungi bwa 1536 μmol cm−2 h−1. Okugezesebwa okw’essaawa 50 kwalaga nti NiV-LDH-NS erina obutebenkevu obulungi kuba esobola okukuuma AA FE waggulu mu MEA (> 80% okumala essaawa 60 ku 200 mA cm−2; > 70% okumala essaawa 58 ku 300 mA cm−2). Kinaamanyibwa nti waliwo obwetaavu okukola AEM ez’amaanyi ennyo okutuuka ku butebenkevu obw’ekiseera ekiwanvu ku densite z’amasannyalaze ezituufu mu makolero. Okugatta ku ekyo, TEA eraga ebirungi mu by’enfuna eby’enkola z’okuddamu okukola AA n’obukulu bw’ebirungo ebikola emirimu egy’amaanyi ne tekinologiya ow’omulembe ow’okwawula okwongera okukendeeza ku nsaasaanya.