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Nts'etsopele ea mahlale a haeterojene e bohareng ba moruo o motala. E le tlhokahalo ea pele ho ho phethahatsa polokelo ea haeterojene, ho hlokahala li-catalyst tse sebetsang le tse tsitsitseng bakeng sa karabelo ea hydrogenation (de)hydrogenation. Ho fihlela joale, sebaka sena se 'nile sa laoloa ke tšebeliso ea litšepe tsa bohlokoa tse turang. Mona, re sisinya catalyst e ncha e theko e tlase e thehiloeng ho cobalt (Co-SAs/NPs@NC) moo libaka tsa tšepe e le 'ngoe tse hasaneng haholo li kopantsoeng ka kopanelo le li-nanoparticles tse ntle ho fihlela ho felisoa ha hydrogenation ea formic acid ka katleho. Ho sebelisoa thepa e ntle ka ho fetisisa ea li-unit tsa CoN2C2 tse hasantsoeng ka athomo le li-nanoparticles tse kentsoeng ka har'a athomo tsa boholo ba 7-8 nm, ho sebelisoa propylene carbonate e le solvent, tlhahiso e ntle ea khase ea 1403.8 ml g-1 h-1 e fumanoe, 'me ha hoa ka ha e-ba le tahlehelo kamora potoloho ea 5. ts'ebetso, e leng betere ka makhetlo a 15 ho feta Pd/C ea khoebo. Liteko tsa tlhahlobo ea sebakeng seo li bontša hore, ha li bapisoa le athomo e le 'ngoe ea tšepe le li-catalyst tsa nanoparticle tse amanang, Co-SAs/NPs@NC e ntlafatsa ho monya le ho kenya tšebetsong ha HCOO* ea bohlokoa ea monodentate, ka hona e khothalletsa karohano ea CH bond e latelang. Lipalo tsa khopolo-taba li bontša hore ho kopanngoa ha li-nanoparticles tsa cobalt ho khothalletsa phetoho ea setsi sa d-band sa athomo e le 'ngoe ea Co hore e be sebaka se sebetsang, ka hona ho ntlafatsa ho kopana pakeng tsa carbonyl O ea HCOO* ea bohareng le setsi sa Co, ka hona ho fokotsa mokoallo oa matla.
Haedrojene e nkuwa e le mojari wa bohlokwa wa eneji bakeng sa phetoho ya hajwale ya eneji ya lefatshe mme e ka ba mokganni wa bohlokwa wa ho fihlella ho se nke lehlakore ha khabone1. Ka lebaka la thepa ya yona ya mmele jwalo ka ho kgona ho tuka le ho ba le bongata bo tlase, polokelo e bolokehileng le e sebetsang hantle le ho tsamaiswa ha haedrojene ke dintlha tsa bohlokwa ho phethahatseng moruo wa haedrojene2,3,4. Bajari ba haedrojene ya metsi a tlhaho (LOHCs), ba bolokang le ho lokolla haedrojene ka diketso tsa dikhemikhale, ba sisintswe e le tharollo. Ha ho bapiswa le haedrojene ya dimolek'hule, dintho tse jwalo (methanol, toluene, dibenzyltoluene, jj.) di bonolo ebile di bonolo ho di tshwara5,6,7. Har'a di-LOHC tse fapaneng tsa setso, formic acid (FA) e na le chefo e tlase haholo (LD50: 1.8 g/kg) le bokgoni ba H2 ba 53 g/L kapa 4.4 wt%. Haholoholo, FA ke yona feela LOHC e ka bolokang le ho lokolla haedrojene tlasa maemo a bobebe ha ho na le di-catalyst tse loketseng, ka hona ha e hloke dikenyo tse kgolo tsa matla a kantle1,8,9. Ha e le hantle, ho se ho entsoe li-catalyst tse ngata tsa tšepe tse ntle bakeng sa ho ntša metsi a formic acid, mohlala, li-catalyst tse thehiloeng ho palladium li sebetsa ka makhetlo a 50-200 ho feta li-catalyst tsa tšepe tse theko e tlaase10,11,12. Leha ho le joalo, haeba u nahana ka litšenyehelo tsa litšepe tse sebetsang, mohlala, palladium e theko e boima ka makhetlo a fetang 1000.
Cobalt, Patlo ea li-catalyst tsa tšepe ea motheo tse sebetsang haholo le tse tsitsitseng e ntse e hohela thahasello ea bafuputsi ba bangata lithutong tsa thuto le indastering13,14,15.
Leha di-catalyst tse theko e tlase tse thehilweng ho Mo le Co, hammoho le di-nanocatalyst tse entsweng ka di-alloy tsa tshepe tse ntle/tse ka tlase, 14,16 di se di hlahisitswe bakeng sa ho ntsha metsi ha FA, ho ntsha metsi ha tsona butle-butle nakong ya karabelo ho ke ke ha qojwa ka lebaka la ho dula ha dibaka tse sebetsang tsa tshepe, CO2, le H2O ke diprothone. kapa di-anion tse bopang (HCOO-), tshilafatso ya FA, ho bokellana ha dikarolwana le chefo ya CO17,18 e ka bang teng. Rona le ba bang re sa tswa bontsha hore di-catalyst tsa athomo e le nngwe (SACs) tse nang le dibaka tse hasaneng haholo tsa CoIINx jwalo ka dibaka tse sebetsang di ntlafatsa reactivity le khanyetso ya asiti ya formic acid dehydrogenation ha e bapiswa le di-nanoparticles17,19,20,21,22,23,24. Disebedisweng tsena tsa Co-NC, diathomo tsa N di sebetsa e le dibaka tse kgolo tsa ho kgothaletsa ho ntsha metsi ha FA ha ho ntse ho ntlafatsa botsitso ba sebopeho ka ho hokahana le athomo ya Co e bohareng, ha diathomo tsa Co di fana ka dibaka tsa ho ntsha metsi ha H mme di kgothaletsa ho ntshwa ha CH22, 25,26. Ka bomalimabe, ts'ebetso le botsitso ba li-catalyst tsena li ntse li le hole le li-catalyst tsa tšepe tse ntle tsa sejoale-joale tse ts'oanang le tse sa tšoaneng (Setšoantšo sa 1) 13.
Matla a feteletseng a tsoang mehloling e nchafatsoang joalo ka letsatsi kapa moea a ka hlahisoa ke electrolysis ea metsi. Haedrojene e hlahisoang e ka bolokoa ho sebelisoa LOHC, mokelikeli oo haedrojene le ho o tlohela o ka fetoloang. Mohatong oa ho o tlohela o ka fetoloa, sehlahisoa se le seng feela ke haedrojene, 'me mokelikeli o jarang o khutlisetsoa boemong ba oona ba pele 'me oa boela oa fetoloa. Haedrojene e ka qetella e sebelisoa liteisheneng tsa peterole, libetering, mehahong ea indasteri le tse ling.
Haufinyane tjena, ho tlalehiloe hore mosebetsi oa ka hare oa li-SAC tse itseng o ka ntlafatsoa boteng ba liathomo tse fapaneng tsa tšepe kapa libaka tse ling tsa tšepe tse fanoang ke li-nanoparticles (NPs) kapa li-nanoclusters (NCs)27,28. Sena se bula menyetla ea ho monya le ho kenya tšebetsong substrate haholoanyane, hammoho le ho fetola sebopeho sa jiometri le sebopeho sa elektroniki sa libaka tsa monatomic. Ka hona, ho monya/ho kenya tšebetsong substrate ho ka ntlafatsoa, ​​​​ho fana ka katleho e ntle ea catalytic ka kakaretso29,30. Sena se re fa mohopolo oa ho theha lisebelisoa tse loketseng tsa catalytic ka libaka tse sebetsang tsa hybrid. Le hoja li-SAC tse ntlafalitsoeng li bontšitse bokhoni bo boholo lits'ebetsong tse fapaneng tsa catalytic, karolo ea tsona polokelong ea haeterojene, ho ea ka tsebo ea rona, ha e hlake. Ntlheng ena, re tlaleha leano le feto-fetohang le le matla bakeng sa ho kopanya li-catalyst tse kopantsoeng le cobalt (Co-SAs/NPs@NCs) tse nang le li-nanoparticles tse hlalositsoeng le litsi tsa tšepe ka bomong. Co-SAs/NPs@NC e ntlafalitsoeng e bonts'a ts'ebetso e ntle ea ho tlosoa ha hydrogenation ea formic acid, e leng betere ho feta li-catalyst tse sa hlomphuoeng hantle (tse kang CoNx, liathomo tse le 'ngoe tsa cobalt, cobalt@NC le γ-Mo2N) esita le li-catalyst tsa tšepe tse ntle. Tlhaloso ea boemo ba kahare le lipalo tsa DFT tsa li-catalyst tse sebetsang li bontša hore libaka tsa tšepe ka bonngoe li sebetsa e le libaka tse sebetsang, 'me li-nanoparticles tsa tlhahiso ena li ntlafatsa setsi sa d-band sa liathomo tsa Co, li khothalletsa ho monya le ho kenya tšebetsong HCOO*, ka hona li fokotsa mokoallo oa matla oa karabelo.
Meralo ea Zeolite imidazolate (ZIFs) ke li-precursor tse hlalositsoeng hantle tse nang le mahlakore a mararo tse fanang ka li-catalyst bakeng sa thepa ea carbonaceous e nang le naetrojene (li-catalyst tsa tšepe-NC) ho tšehetsa mefuta e fapaneng ea litšepe37,38. Ka hona, Co(NO3)2 le Zn(NO3)2 li kopana le 2-methylimidazole ka har'a methanol ho etsa metsoako ea tšepe e tsamaellanang ka har'a tharollo. Kamora ho centrifugation le ho omisa, CoZn-ZIF e ile ea pyrolyzed mochesong o fapaneng (750–950 °C) sepakapakeng sa 6% H2 le 94% Ar. Joalokaha ho bontšitsoe setšoantšong se ka tlase, thepa e hlahisoang e na le litšobotsi tse fapaneng tsa sebaka se sebetsang 'me e bitsoa Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750 (Setšoantšo sa 2a). ). Liteko tse ikhethileng tsa liteko tsa mehato e meng ea bohlokoa ts'ebetsong ea ho kopanya li qaqisitsoe ho Setšoantšo sa 1 le sa 2. C1-C3. Phapang e feto-fetohang ea phofo ea X-ray diffraction (VTXRD) e entsoe ho lekola phetoho ea catalyst. Kamora hore mocheso oa pyrolysis o fihle ho 650 °C, paterone ea XRD e fetoha haholo ka lebaka la ho putlama ha sebopeho sa kristale se laetsoeng sa ZIF (Setšoantšo sa S4) 39. Ha mocheso o ntse o eketseha, litlhōrō tse peli tse pharaletseng li hlaha lipateroneng tsa XRD tsa Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750 ho 20–30° le 40–50°, tse emelang tlhoro ea khabone e sa fetoheng (Setšoantšo sa C5). 40. Hoa hlokomeleha hore ke litlhōrō tse tharo feela tse ikhethang tse ileng tsa bonoa ho 44.2°, 51.5° le 75.8°, tse leng tsa cobalt ea tšepe (JCPDS #15-0806), le 26.2°, tse leng tsa khabone ea graphite (JCPDS # 41-1487). Sekhahla sa X-ray sa Co-SAs/NPs@NC-950 se bonts'a boteng ba li-nanoparticles tsa cobalt tse kang graphite tse kentsoeng holim'a catalyst41,42,43,44. Sekhahla sa Raman se bonts'a hore Co-SAs/NPs@NC-950 e bonahala e na le litlhōrō tse matla le tse tšesaane tsa D le G ho feta lisampole tse ling, e leng se bontšang boemo bo phahameng ba graphitization (Setšoantšo sa S6). Ho phaella moo, Co-SAs/NPs@NC-950 e bonts'a sebaka se phahameng sa Brunner-Emmett-Taylor (BET) le bophahamo ba pore (1261 m2 g-1 le 0.37 cm3 g-1) ho feta lisampole tse ling 'me boholo ba ZIF ke thepa ea NC derivatives. (Setšoantšo sa S7 le Tafole ea S1). Sebopeho-pono sa ho monya ha athomo (AAS) se bontsha hore dikahare tsa cobalt tsa Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 le Co-SAs/NPs@ ke 2.69 wt%, 2.74 % wt. le 2.73% wt. NC-750 ka ho latellana (Tafole S2). Dikahare tsa Zn tsa Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750 di eketseha butle-butle, e leng se bakwang ke phokotso e eketsehileng le ho fetoha ha diyuniti tsa Zn. Keketseho ya mocheso wa pyrolysis (Zn, ntlha e belang = 907 °C) 45.46. Tlhahlobo ya elemental (EA) e bontshitse hore peresente ya N e a fokotseha ka mocheso o ntseng o eketseha wa pyrolysis, mme dikahare tse hodimo tsa O2 di ka bakwa ke ho monywa ha molek'hule ya O2 ho tloha ha e pepesehela moya. (Tafole S3). Ka tekanyo e itseng ea cobalt, li-nanoparticles le li-coatom tse arohaneng lia kopana, e leng se fellang ka keketseho e kholo ea ts'ebetso ea catalyst, joalo ka ha ho buisanoe ka tlase.
Setšoantšo sa sebopeho sa motsoako oa Co-SA/NPs@NC-T, moo T e leng mocheso oa pyrolysis (°C). b setšoantšo sa TEM. c Setšoantšo sa Co-SAs/NPs@NC-950 AC-HAADF-STEM. Liathomo tsa Co ka bomong li tšoailoe ka li-circles tse khubelu. d Template ea EDS Co-SA/NPs@NC-950.
Haholo-holo, microscopy ea elektrone ea phetisetso (TEM) e bontšitse boteng ba li-nanoparticles tse fapaneng tsa cobalt (NPs) tse nang le boholo bo tloaelehileng ba 7.5 ± 1.7 nm feela ho Co-SA/NPs@NC-950 (Litšoantšo tsa 2 b le S8). Li-nanoparticles tsena li koahetsoe ka carbon e kang graphite e nang le naetrojene. Sebaka sa lattice fringe sa 0.361 le 0.201 nm se tsamaellana le likaroloana tsa graphite carbon (002) le Co (111) ea tšepe, ka ho latellana. Ho phaella moo, microscopy ea elektrone ea phetisetso ea annular dark-field scanning e nang le angle e phahameng (AC-HAADF-STEM) e senotse hore li-NP tsa Co-SAs/NPs@NC-950 li ne li pota-potiloe ke cobalt e ngata ea athomo (Setšoantšo sa 2c). Leha ho le joalo, ke liathomo tsa cobalt tse hasaneng ka athomo feela tse ileng tsa bonoa tšehetsong ea lisampole tse ling tse peli (Setšoantšo sa S9). Setšoantšo sa HAADF-STEM sa Energy dispersive spectroscopy (EDS) se bonts'a kabo e ts'oanang ea C, N, Co le Co NPs tse arohaneng ho Co-SAs/NPs@NC-950 (Setšoantšo sa 2d). Liphetho tsena kaofela li bonts'a hore litsi tsa Co tse hasantsoeng ka athomo le li-nanoparticles tse kentsoeng ka har'a khabone e kang ea graphite e nang le N li hokahantsoe ka katleho ho li-substrate tsa NC ho Co-SAs/NPs@NC-950, ha litsi tsa tšepe tse arohaneng feela.
Boemo ba valence le sebopeho sa lik'hemik'hale tsa thepa e fumanoeng li ithutiloe ka X-ray photoelectron spectroscopy (XPS). Li-spectra tsa XPS tsa li-catalyst tse tharo li bontšitse boteng ba likarolo Co, N, C le O, empa Zn e ne e le teng feela ho Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750 (Setšoantšo sa 2). ). C10). Ha mocheso oa pyrolysis o ntse o eketseha, kakaretso ea naetrojene ea fokotseha ha mefuta ea naetrojene e fetoha e sa tsitsang 'me e bola ho ba likhase tsa NH3 le NOx mochesong o phahameng (Tafole ea S4) 47. Kahoo, kakaretso ea khabone e ile ea eketseha butle-butle ho tloha ho Co-SAs/NPs@NC-750 ho ea ho Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-950 (Litšoantšo S11 le S12). Sampole e pyrolyzed mochesong o phahameng e na le karolo e tlase ea liathomo tsa naetrojene, ho bolelang hore palo ea lijari tsa NC ho Co-SAs/NPs@NC-950 e lokela ho ba tlase ho feta ea lisampoleng tse ling. Sena se lebisa ho silafatseng ha dikarolwana tsa cobalt ka matla. Sepektara sa O 1s se bontsha dihlopha tse pedi tsa C=O (531.6 eV) le C–O (533.5 eV), ka ho latellana (Setshwantsho S13) 48. Jwalo ka ha ho bontshitswe ho Setshwantsho sa 2a, sepektara sa N 1s se ka rarollwa ho ba dihlopha tse nne tse ikgethang tsa pyridine nitrogen N (398.4 eV), pyrrole N (401.1 eV), graphite N (402.3 eV) le Co-N (399.2 eV). Ditlamo tsa Co-N di teng disampoleng tsohle tse tharo, ho bontsha hore diathomo tse ding tsa N di hokahantswe le dibaka tsa monometallic, empa dibopeho di fapana haholo49. Tshebediso ya mocheso o phahameng wa pyrolysis e ka fokotsa haholo dikahare tsa mefuta ya Co-N ho tloha ho 43.7% ho Co-SA/NPs@NC-750 ho isa ho 27.0% ho Co-SAs/NPs@NC-850 le Co 17.6%@ NC-950. ho -CA/NPs, e tsamaellanang le keketseho ea dikahare tsa C (Setshwantsho sa 3a), e bontshang hore palo ya tsona ya ho hokahanya Co-N e ka fetoha mme ya nkeloa sebaka ka karolo e itseng ke diathomo tsa C50. Sekgahla sa Zn 2p se bontsha hore karolo ena e teng haholo-holo ka sebopeho sa Zn2+. (Setshwantsho sa S14) 51. Sekgahla sa Co 2p se bontsha ditlhōrō tse pedi tse hlahelletseng ho 780.8 le 796.1 eV, tse amanang le Co 2p3/2 le Co 2p1/2, ka ho latellana (Setshwantsho sa 3b). Ha ho bapiswa le Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750, tlhoro ya Co-N ho Co-SAs/NPs@NC-950 e fetisetswa lehlakoreng le letle, e bontshang hore athomo e le nngwe ya Co ho ya hodima -SAs/NPs@NC-950 e na le tekanyo e hodimo ya ho fela ha dielektrone, e leng se fellang ka boemo bo hodimo ba oxidation. Hoa hlokomeleha hore ke Co-SAs/NPs@NC-950 feela e bonts'itseng tlhoro e fokolang ea cobalt (Co0) ea zero-valent ho 778.5 eV, e leng se pakang boteng ba li-nanoparticles tse bakoang ke ho bokellana ha cobalt SA mochesong o phahameng.
a N 1s le b Co 2p spectra ea Co-SA/NPs@NC-T. c XANES le d FT-EXAFS spectra ea Co-K-edge ea Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750. e WT-EXAFS contour plots ea Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850, le Co-SAs/NPs@NC-750. f FT-EXAFS fitting curve bakeng sa Co-SA/NPs@NC-950.
Sesepa-pono sa ho monya X-ray se koetsoeng ka nako (XAS) se ile sa sebelisoa ho sekaseka sebopeho sa elektroniki le tikoloho ea tšebelisano ea mofuta oa Co sampole e lokisitsoeng. Maemo a Cobalt valence ho Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750 Sebopeho sa Edge se senotsoe ke ho monya X-ray e haufi le tšimo e tloaelehileng ea Co-K edge (XANES) spectrum. Joalokaha ho bontšitsoe ho Setšoantšo sa 3c, ho monya haufi le moeli oa lisampole tse tharo ho pakeng tsa lifoile tsa Co le CoO, ho bontšang hore boemo ba valence ba mofuta oa Co bo tloha ho 0 ho isa ho +253. Ho phaella moo, phetoho ho ea ho matla a tlase e ile ea bonoa ho tloha ho Co-SAs/NPs@NC-950 ho ea ho Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750, ho bontšang hore Co-SAs/NPs@NC-750 e na le boemo bo tlase ba oxidation. Ho ya ka diphetho tsa ho kopanya ka mola o otlolohileng, boemo ba Co valence ba Co-SAs/NPs@NC-950 bo hakanngwa ho ba +0.642, e leng tlase ho boemo ba Co valence ba Co-SAs/NPs@NC-850 (+1.376). Co-SA/NP @NC-750 (+1.402). Diphetho tsena di bontsha hore boemo bo tloaelehileng ba oxidation ba dikarolwana tsa cobalt ho Co-SAs/NPs@NC-950 bo fokotsehile haholo, e leng se tsamaellanang le diphetho tsa XRD le HADF-STEM mme se ka hlaloswa ka ho ba teng ha di-nanoparticles tsa cobalt le cobalt e le nngwe. Liathomo tsa Co 41. Sekhahla sa sebopeho se setle sa ho monya X-ray (FT-EXAFS) sa Co K-edge se bontsha hore tlhoro e kgolo ho 1.32 Å ke ya khetla ya Co-N/Co-C, ha tsela ya ho hasana ha Co-Co ya tshepe e le ho 2.18 feela ho Co-SAs Å e fumanwang ho /NPs@NC-950 (Setshwantsho sa 3d). Ho feta moo, moralo wa contour wa wavelet transform (WT) o bontsha matla a hodimo ho 6.7 Å-1 a bakwang ke Co-N/Co-C, ha Co-SAs/NPs@NC-950 feela e bontshang matla a hodimo a bakwang ke 8.8. Matla a mang a hodimo a bakwang ke Å−1 ho tlamo ya Co-Co (Setshwantsho sa 3e). Ho phaella moo, tlhahlobo ea EXAFS e entsoeng ke mohiri e bontšitse hore mochesong oa pyrolysis oa 750, 850 le 950 °C, linomoro tsa khokahano ea Co-N e ne e le 3.8, 3.2 le 2.3, ka ho latellana, 'me linomoro tsa khokahano ea Co-C e ne e le 0. 0.9 le 1.8 (Setšoantšo sa 3f, S15 le Tafole ea S1). Haholo-holo, liphetho tsa morao-rao li ka amahanngoa le boteng ba li-unit tsa CoN2C2 tse hasaneng ka athomo le li-nanoparticles ho Co-SAs/NPs@NC-950. Ka lehlakoreng le leng, ho Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750, ke li-unit tsa CoN3C le CoN4 feela tse teng. Ho totobetse hore ka mocheso o ntseng o eketseha oa pyrolysis, liathomo tsa N yuniti ea CoN4 li nkeloa sebaka butle-butle ke liathomo tsa C, 'me cobalt CA ea kopana ho etsa li-nanoparticles.
Maemo a karabelo a neng a ithutoa pele a ne a sebedisetswa ho ithuta phello ya maemo a ho lokisa hodima thepa ya thepa e fapaneng (Setshwantsho S16)17,49. Jwalo ka ha ho bontshitswe ho Setshwantsho sa 4 a, mosebetsi wa Co-SAs/NPs@NC-950 o phahame haholo ho feta wa Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750. Haholoholo, disampole tsohle tse tharo tsa Co tse lokisitsweng di bontshitse tshebetso e phahameng ha di bapiswa le di-catalyst tsa tshepe ya bohlokwa tse tlwaelehileng tsa kgwebo (Pd/C le Pt/C). Ho phaella moo, disampole tsa Zn-ZIF-8 le Zn-NC di ne di sa sebetse ho ya ho dehydrogenation ya formic acid, e leng se bontshang hore dikarolwana tsa Zn ha se dibaka tse sebetsang, empa phello ya tsona mosebetsing ha e na thuso. Ho feta moo, mosebetsi wa Co-SAs/NPs@NC-850 le Co-SAs/NPs@NC-750 o ile wa feta pyrolysis ya bobedi ho 950°C ka hora e le nngwe, empa o ne o le tlase ho feta wa Co-SAs/NPs@NC-750. @NC-950 (Setšoantšo sa S17). Tlhaloso ea sebopeho sa thepa ena e bontšitse boteng ba li-nanoparticles tsa Co lisampoleng tse entsoeng hape ka pyrolyze, empa sebaka se tlase sa bokaholimo le ho ba sieo ha carbon e kang graphite ho bakile ts'ebetso e tlase ha ho bapisoa le Co-SAs/NPs@NC-950 (Setšoantšo sa S18–S20). Ts'ebetso ea lisampole tse nang le litekanyo tse fapaneng tsa pele ho Co le eona e bapisitsoe, ka ts'ebetso e phahameng ka ho fetisisa e bontšitsoeng ho 3.5 mol e ekelitsoeng (Tafole ea S6 le Setšoantšo sa S21). Ho totobetse hore ho thehoa ha litsi tse fapaneng tsa tšepe ho susumetsoa ke litaba tsa haedrojene sepakapakeng sa pyrolysis le nako ea pyrolysis. Ka hona, thepa e meng ea Co-SAs/NPs@NC-950 e ile ea hlahlojoa bakeng sa ts'ebetso ea formic acid dehydrogenation. Lisebelisoa tsohle li bontšitse ts'ebetso e mahareng ho isa ho e ntle haholo; leha ho le joalo, ha ho le e 'ngoe ea tsona e neng e le betere ho feta Co-SAs/NPs@NC-950 (Setšoantšo sa S22 le S23). Tlhaloso ea sebopeho sa thepa e bontšitse hore ka nako e ntseng e eketseha ea pyrolysis, litaba tsa maemo a monoatomic Co-N li fokotseha butle-butle ka lebaka la ho kopana ha liathomo tsa tšepe ho li-nanoparticles, e leng se hlalosang phapang ea ts'ebetso lipakeng tsa lisampole tse nang le nako ea pyrolysis ea 100-2000. phapang ke 0.5 h, 1 h, le 2 h (Litšoantšo S24–S28 le Tafole S7).
Kerafo ea bophahamo ba khase khahlanong le nako e fumanoeng nakong ea ho ntšoa ha liboka tsa mafura ho sebelisoa li-catalyst tse fapaneng. Maemo a karabelo: FA (10 mmol, 377 μl), catalyst (30 mg), PC (6 ml), Tback: 110 °C, Tactical: 98 °C, likarolo tse 4 b Co-SAs/NPs@NC-950 (30 mg), li-solvent tse fapaneng. c Papiso ea sekhahla sa ho iphetola ha khase ea li-catalyst tse sa tšoaneng ka har'a li-solvent tsa tlhaho ho 85–110 °C. d Teko ea ho sebelisa hape Co-SA/NPs@NC-950. Maemo a karabelo: FA (10 mmol, 377 µl), Co-SAs/NPs@NC-950 (30 mg), solvent (6 ml), Tback: 110 °C, Tactical: 98 °C, potoloho e 'ngoe le e 'ngoe ea karabelo e nka hora e le 'ngoe. Li-bar tsa liphoso li emela liphapang tse tloaelehileng tse baloang ho tsoa litekong tse tharo tse sebetsang.
Ka kakaretso, katleho ea li-catalyst tsa dehydrogenation tsa FA e itšetlehile haholo ka maemo a karabelo, haholo-holo tharollo e sebelisitsoeng8,49. Ha ho sebelisoa metsi e le tharollo, Co-SAs/NPs@NC-950 e bontšitse sekhahla se phahameng ka ho fetisisa sa karabelo ea pele, empa ho emisoa ho etsahetse, mohlomong ka lebaka la liprothone kapa H2O18 tse lulang libakeng tse sebetsang. Teko ea catalyst li-solvent tsa organic tse kang 1,4-dioxane (DXA), n-butyl acetate (BAC), toluene (PhMe), triglyme le cyclohexanone (CYC) le tsona ha lia ka tsa bontša ntlafatso efe kapa efe, le ho propylene carbonate (PC)) (Setšoantšo sa 4b le Tafole ea S8). Ka ho tšoanang, li-additives tse kang triethylamine (NEt3) kapa sodium formate (HCCONA) ha lia ka tsa ba le phello e ntle ts'ebetsong ea catalyst (Setšoantšo sa S29). Tlas'a maemo a karabelo a matle, tlhahiso ea khase e fihlile ho 1403.8 mL g−1 h−1 (Setšoantšo sa S30), e neng e le holimo haholo ho feta li-catalyst tsohle tsa Co tse tlalehiloeng pele (ho kenyeletsoa le SAC17, 23, 24). Litekong tse fapaneng, ho sa kenyeletsoe li-reaction ka metsing le ka li-additives tsa formate, ho ile ha fumanoa khetho ho fihlela ho 99.96% bakeng sa ho tlosoa ha haeterojene le ho felloa ke metsi 'meleng (Tafole ea S9). Matla a ho kenya tšebetsong a baliloeng ke 88.4 kJ/mol, a bapisoang le matla a ho kenya tšebetsong a li-catalyst tsa tšepe tse ntle (Setšoantšo sa S31 le Tafole ea S10).
Ho phaella moo, re bapisitse di-catalyst tse ding tse ngata tse sa tshwaneng bakeng sa ho fellwa ha hydrogenation ya formic acid tlasa maemo a tshwanang (Setshwantsho sa 4c, ditafole tsa S11 le S12). Jwalo ka ha ho bontshitswe Setshwantshong sa 3c, sekgahla sa tlhahiso ya kgase sa Co-SAs/NPs@NC-950 se feta sa di-catalyst tsa tshepe ya motheo tse tsebahalang haholo tse sa tshwaneng mme se phahame ka makgetlo a 15 le a 15 ho feta sa 5% Pd/C ya kgwebo le 5% Pd/C, ka ho latellana. hang. % Pt/C catalyst.
Tšobotsi ea bohlokoa ea ts'ebeliso efe kapa efe e sebetsang ea li-catalyst tsa (de)hydrogenation ke botsitso ba tsona. Ka hona, letoto la liteko tsa ho sebelisa hape tse sebelisang Co-SAs/NPs@NC-950 li ile tsa etsoa. ​​Joalokaha ho bontšitsoe ho Setšoantšo sa 4 d, ts'ebetso ea pele le khetho ea thepa li ile tsa lula li sa fetoha nakong ea makhetlo a mahlano a latellanang (sheba hape Tafole ea S13). Liteko tsa nako e telele li ile tsa etsoa 'me tlhahiso ea khase ea eketseha ka tatellano ho feta lihora tse 72 (Setšoantšo sa S32). Boleng ba cobalt ba Co-SA/NPs@NC-950 e sebelisitsoeng e ne e le 2.5 wt%, e leng se neng se le haufi haholo le sa catalyst e ncha, e leng se bontšang hore ho ne ho se na leaching e totobetseng ea cobalt (Tafole ea S14). Ha ho phetoho e totobetseng ea 'mala kapa pokello ea likaroloana tsa tšepe e ileng ea bonoa pele le ka mor'a karabelo (Setšoantšo sa S33). AC-HAADF-STEM le EDS ea thepa e sebelisitsoeng litekong tsa nako e telele li bontšitse ho bolokoa le ho hasana ho ts'oanang ha libaka tsa ho hasana ha athomo 'me ha ho liphetoho tse kholo tsa sebopeho (Litšoantšo tsa S34 le S35). Litlhōrō tse ikhethang tsa Co0 le Co-N li ntse li le teng ho XPS, e leng se pakang ho ba teng ha li-NP tsa Co le libaka tsa tšepe ka bonngoe, e leng se tiisang botsitso ba catalyst ea Co-SAs/NPs@NC-950 (Setšoantšo sa S36).
Ho hlwaya dibaka tse sebetsang ka ho fetisisa tse ikarabellang bakeng sa ho ntshuwa ha asiti ya formic, disebediswa tse kgethilweng tse nang le setsi se le seng feela sa tshepe (CoN2C2) kapa Co NP di lokisitswe ho latela dithuto tse fetileng17. Tatellano ya mosebetsi wa ho ntshuwa ha asiti ya formic e bonweng tlasa maemo a tshwanang ke Co-SAs/NPs@NC-950 > Co SA > Co NP (Tafole S15), e bontshang hore dibaka tsa CoN2C2 tse hasantsweng ka athomo di sebetsa ho feta NPs. Kinetics ya karabelo e bontsha hore phetoho ya haeterojene e latela kinetics ya karabelo ya taelo ya pele, empa matsoapo a di-curve tse mmalwa dikahareng tse fapaneng tsa cobalt ha a tshwane, e bontshang hore kinetics ha e itshetlehe feela ka formic acid, empa hape le sebakeng se sebetsang (Setshwantsho sa 2). C37). Diphuputso tse ding tsa kinetic di bontshitse hore, ka lebaka la ho se be teng ha ditlhōrō tsa tshepe ya cobalt tlhahlobong ya diffraction ya X-ray, tatellano ya kinetic ya karabelo mabapi le dikahare tsa cobalt e fumanwe e le 1.02 maemong a tlase (ka tlase ho 2.5%), e bontshang kabo e batlang e tshwana ya ditsi tsa cobalt tsa monoatomic. tse ka sehloohong. sebaka se sebetsang (litšoantšo tsa S38 le S39). Ha dikahare tsa dikahare tsa Co di fihla ho 2.7%, r e eketseha ka tshohanyetso, e leng se bontshang hore dikahare tsa nano di sebelisana hantle le diathomo tse ikgethang ho fumana mosebetsi o phahameng. Ha dikahare tsa dikahare tsa Co di ntse di eketseha, moedi o fetoha o sa tsamaellaneng, o amanang le keketseho ya palo ya dikahare tsa nano le phokotseho ya maemo a monatomiki. Kahoo, tshebetso e ntlafetseng ya ho ntsha hydrogenation ya LC ya Co-SA/NPs@NC-950 e hlaha ka lebaka la boitshwaro ba tshebedisano mmoho ya dibaka tsa tshepe le dikahare tsa nano.
Phuputso e tebileng e entsoe ho sebelisoa in situ diffuse reflectance Fourier transform (in situ DRIFT) ho khetholla li-intermediate tsa reaction ts'ebetsong. Kamora ho futhumatsa disampole mochesong o fapaneng oa reaction kamora ho eketsa formic acid, ho ile ha bonoa lihlopha tse peli tsa maqhubu (Setšoantšo sa 5a). Litlhōrō tse tharo tse ikhethang tsa HCOOH* li hlaha ho 1089, 1217 le 1790 cm-1, tse amanang le ho thothomela ha CH π (CH) kantle ho sefofane, ho thothomela ha CO ν (CO) le ho thothomela ha C=O ν (C=O) ho thothomela, 54, 55 ka ho latellana. Sete e 'ngoe ea litlhōrō ho 1363 le 1592 cm-1 e tsamaellana le ho thothomela ha OCO ho tšoanang νs(OCO) le ho thothomela ha OCO ho sa lekanang νas(OCO)33.56 HCOO*, ka ho latellana. Ha karabelo e ntse e tsoela pele, litlhōrō tse amanang tsa HCOOH* le HCOO* lia fokola butle-butle. Ka kakaretso, ho bola ha formic acid ho kenyelletsa mehato e meraro e meholo: (I) ho monya formic acid libakeng tse sebetsang, (II) ho tlosoa ha H ka tsela ea formate kapa carboxylate, le (III) ho kopanngoa ha H tse peli tse monyang ho hlahisa haeterojene. HCOO* le COOH* ke li-intermediate tsa bohlokoa ho khetholleng litsela tsa formate kapa carboxylate, ka ho latellana57. Tsamaisong ea rona ea catalytic, ke tlhōrō ea HCOO* feela e hlahelletseng, e bontšang hore ho bola ha formic acid ho etsahala feela ka tsela ea formic acid58. Ho ile ha etsoa litebello tse tšoanang mochesong o tlase oa 78 °C le 88 °C (setšoantšo sa S40).
Li-spectra tsa DRIFT tsa ho felisoa ha HCOOH ke oksijene ho Co-SAs/NPs@NC-950 le b Co SAs. Tšōmo e bontša linako tsa karabelo sebakeng seo. c Matla a bophahamo ba khase a fumanoeng ho sebelisoa li-reagent tse fapaneng tsa ho ngola li-isotope. d Lintlha tsa phello ea isotope ea Kinetic.
Liteko tse tšoanang tsa DRIFT li entsoe holim'a lisebelisoa tse amanang le Co NP le Co SA ho ithuta phello ea tšebelisano-'moho ho Co-SA/NPs@NC-950 (Litšoantšo tsa 5 b le S41). Lisebelisoa ka bobeli li bontša mekhoa e tšoanang, empa litlhōrō tse ikhethang tsa HCOOH* le HCOO* li fetotsoe hanyane, ho bontša hore ho kenyelletsoa ha Co NPs ho fetola sebopeho sa elektroniki sa setsi sa monoatomic. Tlhōrō e ikhethang ea νas(OCO) e hlaha ho Co-SAs/NPs@NC-950 le Co SA empa eseng ho Co NPs, e leng se bontšang hore karolo e bohareng e entsoeng ha ho eketsoa formic acid ke monodentate formic acid e otlolohileng holim'a letsoai la sefofane. 'me e khomaretsoe ho SA e le sebaka se sebetsang 59. Hoa hlokomeleha hore keketseho e kholo ea ho thothomela ha litlhōrō tse ikhethang tsa π(CH) le ν(C = O) e ile ea bonoa, e leng se ileng sa lebisa ho sotheheng ha HCOOH* le ho nolofatsa karabelo. Ka lebaka leo, litlhōrō tse ikhethang tsa HCOOH* le HCOO* ho Co-SAs/NPs@NC li batlile li nyamela kamora metsotso e 2 ea karabelo, e leng se potlakileng ho feta sa li-catalyst tse thehiloeng ho monometallic (metsotso e 6) le nanoparticle (metsotso e 12). . Liphetho tsena kaofela li tiisa hore ho sebelisa nanoparticle ho ntlafatsa ho monya le ho kenya tšebetsong ha li-intermediate, ka hona ho potlakisa liketso tse hlahisitsoeng ka holimo.
Ho sekaseka tsela ea karabelo haholoanyane le ho fumana mohato oa ho fumana sekhahla (RDS), phello ea KIE e entsoe boteng ba Co-SAs/NPs@NC-950. Mona, li-isotope tse fapaneng tsa formic acid tse kang HCOOH, HCOOD, DCOOH le DCOOD li sebelisoa bakeng sa lithuto tsa KIE. Joalokaha ho bontšitsoe ho Setšoantšo sa 5c, sekhahla sa ho haella ha oksijene se fokotseha ka tatellano e latelang: HCOOH > HCOOD > DCOOH > DCOOD. Ho phaella moo, boleng bo baliloeng ba KHCOOH/KHCOOD, KHCOOH/KDCOOH, KHCOOD/KDCOOD le KDCOOH/KDCOOD e ne e le 1.14, 1.71, 2.16 le 1.44, ka ho latellana (Setšoantšo sa 5d). Ka hona, karohano ea CH bond ho HCOO* e bontša boleng ba kH/kD ​​>1.5, e bontšang phello e kholo ea kinetic60,61, 'me e bonahala e emela RDS ea ho felisoa ha HCOOH ho Co-SAs/NPs@NC-950.
Ho phaella moo, dipalo tsa DFT di entswe ho utlwisisa phello ya di-nanoparticles tse nang le doped mosebetsing wa ka hare wa Co-SA. Mehlala ya Co-SAs/NPs@NC le Co-SA e hahilwe ho latela diteko tse bontshitsweng le mesebetsi e fetileng (Ditshwantsho tsa 6a le S42)52,62. Kamora ntlafatso ya jeometri, di-nanoparticles tse nyane tsa Co6 (CoN2C2) tse tsamaisanang le diyuniti tsa monoatomic di ile tsa hlwauwa, mme bolelele ba dibopeho tsa Co-C le Co-N ho Co-SA/NPs@NC bo ile ba fumanwa e le 1.87 Å le 1.90 Å, ka ho latellana. , e leng se tsamaellanang le diphetho tsa XAFS. Bongata ba karolo e balwang ba maemo (PDOS) bo bontsha hore athomo ya tshepe ya Co e le nngwe le nanoparticle composite (Co-SAs/NPs@NC) di bontsha ho kopanya ho hoholo haufi le boemo ba Fermi ha ho bapiswa le CoN2C2, e leng se fellang ka HCOOH. Phetiso ya elektrone e bolileng e sebetsa hantle haholo (Ditshwantsho tsa 6b le S43). Litsi tsa d-band tse tsamaellanang tsa Co-SAs/NPs@NC le Co-SA li baliloe ho ba -0.67 eV le -0.80 eV, ka ho latellana, tseo har'a tsona keketseho ea Co-SAs/NPs@NC e neng e le 0.13 eV, e leng se ileng sa tlatsetsa hore ka mor'a ho hlahisoa ha NP, ho kenngoa ha likaroloana tsa HCOO* ka sebopeho sa elektroniki se fetotsoeng sa CoN2C2 hoa etsahala. Phapang ea bongata ba tjhaja e bontša leru le leholo la electron ho potoloha boloko ba CoN2C2 le nanoparticle, e leng se bontšang tšebelisano e matla lipakeng tsa tsona ka lebaka la phapanyetsano ea electron. Ha e kopantsoe le tlhahlobo ea tjhaja ea Bader, ho fumanoe hore Co e hasantsoeng ka athomo e lahlehetsoe ke 1.064e ho Co-SA/NPs@NC le 0.796e ho Co SA (Setšoantšo sa S44). Liphetho tsena li bontša hore ho kopanngoa ha nanoparticles ho lebisa ho fokotseheng ha li-elektrone tsa libaka tsa Co, ho fellang ka keketseho ea Co valence, e lumellanang le liphetho tsa XPS (Setšoantšo sa 6c). Litšobotsi tsa tšebelisano-'moho ea Co-O tsa adsorption ea HCOO ho Co-SAs/NPs@NC le Co SA li hlahlobiloe ka ho bala sehlopha sa Hamiltonian sa kristale (COHP)63. Joalokaha ho bontšitsoe ho Setšoantšo sa 6 d, boleng bo bobe le bo botle ba -COHP bo tsamaellana le boemo ba antibonding le boemo ba ho tlama, ka ho latellana. Matla a bonto ea Co-O a amohuoeng ke HCOO (Co-carbonylOH HCOO*) a hlahlobiloe ka ho kopanya boleng ba -COHP, bo neng bo le 3.51 le 3.38 bakeng sa Co-SAs/NPs@NC le Co-SA, ka ho latellana. Adsorption ea HCOOH le eona e bontšitse liphetho tse tšoanang: keketseho ea boleng bo kopaneng ba -COHP kamora ho sebelisa nanoparticle doping e bontšitse keketseho ea bonto ea Co-O, ka hona e khothalletsa ts'ebetso ea HCOO le HCOOH (Setšoantšo sa S45).
Sebopeho sa lattice sa Co-SA/NPs@NC-950. b PDOS Co-SA/NP@NC-950 le Co SA. c 3D isosurface ea phapang ea bongata ba charge ea HCOOH adsorption ho Co-SA/NPs@NC-950 le Co-SA. (d) pCOHP ea libonto tsa Co-O tse amohuoang ke HCOO ho Co-SA/NPs@NC-950 (ka letsohong le letšehali) le Co-SA (ka letsohong le letona). e Tsela ea karabelo ea HCOOH dehydrogenation ho Co-SA/NPs@NC-950 le Co-SA.
Ho utloisisa hamolemo ts'ebetso e phahameng ea ho tlosoa ha hydrogenation ea Co-SA/NPs@NC, tsela ea karabelo le matla li thehiloe. Ka ho khetheha, ho tlosoa ha FA ho kenyelletsa mehato e mehlano, ho kenyeletsoa le phetoho ea HCOOH ho HCOOH*, HCOOH* ho HCOO* + H*, HCOO* + H* ho 2H* + CO2*, 2H* + CO2* ho 2H* + CO2, le 2H* ho H2 (Setšoantšo sa 6e). Matla a ho kenngoa ha limolek'hule tsa formic acid holim'a catalyst ka oksijene ea carboxylic a tlase ho feta ka oksijene ea hydroxyl (Litšoantšo tsa S46 le S47). Ka mor'a moo, ka lebaka la matla a tlase, adsorbate ka ho khetheha e feta karohanong ea OH bond ho theha HCOO* ho fapana le karohano ea CH bond ho theha COOH*. Ka nako e ts'oanang, HCOO* e sebelisa monodentate adsorption, e khothalletsang ho robeha ha litlamo le ho thehoa ha CO2 le H2. Liphetho tsena li tsamaellana le boteng ba tlhōrō ea νas(OCO) ka har'a DRIFT ea in situ, e leng se bontšang hore ho senyeha ha FA ho etsahala ka tsela ea formate thutong ea rona. Ho bohlokoa ho hlokomela hore ho ea ka litekanyo tsa KIE, karohano ea CH e na le thibelo e phahameng haholo ea matla a karabelo ho feta mehato e meng ea karabelo 'me e emela RDS. Thibelo ea matla ea sistimi e ntle ea li-catalyst tsa Co-SAs/NPs@NC e tlase ka 0.86 eV ho feta ea Co-SA (1.2 eV), e ntlafatsang haholo katleho ea ho tlosoa ha hydrogenation ka kakaretso. Haholo-holo, boteng ba li-nanoparticles bo laola sebopeho sa elektroniki sa libaka tsa coactive tse hasaneng ka athomo, e leng se ntlafatsang ho monya le ho kenya tšebetsong ha li-intermediate, ka hona ho fokotsa thibelo ea karabelo le ho khothaletsa tlhahiso ea haetrojene.
Ka bokhutšoanyane, re bontša ka lekhetlo la pele hore ts'ebetso ea catalytic ea li-catalyst tsa tlhahiso ea haedrojene e ka ntlafatsoa haholo ka ho sebelisa thepa e nang le litsi tsa monometallic tse ajoang haholo le li-nanoparticles tse nyane. Khopolo ena e netefalitsoe ke ho kopanngoa ha li-catalyst tsa tšepe ea athomo e le 'ngoe tse thehiloeng ho cobalt tse fetotsoeng ka li-nanoparticles (Co-SAs/NPs@NC), hammoho le thepa e amanang le eona e nang le litsi tsa tšepe e le 'ngoe feela (CoN2C2) kapa Co NPs. Lisebelisoa tsohle li lokisitsoe ka mokhoa o bonolo oa pyrolysis oa mohato o le mong. Tlhahlobo ea sebopeho e bontša hore catalyst e ntle ka ho fetisisa (Co-SAs/NPs@NC-950) e na le li-unit tsa CoN2C2 tse hasantsoeng ka athomo le li-nanoparticles tse nyane (7-8 nm) tse nang le naetrojene le khabone e kang graphite. E na le tlhahiso e ntle ea khase ho fihlela ho 1403.8 ml g-1 h-1 (H2:CO2 = 1.01:1), khetho ea H2 le CO ea 99.96% 'me e ka boloka ts'ebetso e sa khaotseng matsatsi a' maloa. Mosebetsi oa catalyst ena o feta mosebetsi oa li-catalyst tse itseng tsa Co SA le Pd/C ka makhetlo a 4 le a 15, ka ho latellana. Liteko tsa DRIFT li bontša hore ha li bapisoa le Co-SA, Co-SAs/NPs@NC-950 e bontša adsorption e matla ea monodentate ea HCOO*, e leng ea bohlokoa bakeng sa tsela ea formate, 'me li-nanoparticles tsa dopant li ka khothaletsa ts'ebetso ea HCOO* le ho potlakisa C-H. Karohano ea bond e ile ea khetholloa e le RDS. Lipalo tsa khopolo-taba li bontša hore doping ea Co NP e eketsa setsi sa d-band sa liathomo tsa Co e le 'ngoe ka 0.13 eV ka tšebelisano, e ntlafatsa adsorption ea li-intermediate tsa HCOOH* le HCOO*, ka hona e fokotsa mokoallo oa karabelo ho tloha ho 1.20 eV bakeng sa Co SA ho ea ho 0 .86 eV. O ikarabella bakeng sa ts'ebetso e ikhethang.
Ka kakaretso, phuputso ena e fana ka mehopolo bakeng sa moralo oa li-catalyst tse ncha tsa tšepe ea athomo e le 'ngoe' me e ntšetsa pele kutloisiso ea mokhoa oa ho ntlafatsa ts'ebetso ea catalytic ka phello ea tšebelisano-'moho ea litsi tsa tšepe tsa boholo bo fapaneng. Re lumela hore mokhoa ona o ka atolosoa habonolo ho litsamaiso tse ling tse ngata tsa catalytic.
Co(NO3)2 6H2O (AR, 99%), Zn(NO3)2 6H2O (AR, 99%), 2-methylimidazole (98%), methanol (99.5%), propylene carbonate (PC, 99%) ethanol (AR, 99.7%) e rekiloe ho McLean, Chaena. Formic acid (HCOOH, 98%) e rekiloe ho tsoa Rhawn, Chaena. Li-reagent tsohle li sebelisitsoe ka kotloloho ntle le tlhoekiso e eketsehileng, 'me metsi a hloekileng haholo a lokisitsoe ho sebelisoa sistimi ea tlhoekiso e hloekileng haholo. Pt/C (5% boima bo jarolloang) le Pd/C (5% boima bo jarolloang) li rekiloe ho Sigma-Aldrich.
Ho kopanngoa ha likristale tsa CoZn-ZIF ho entsoe ho latela mekhoa e fetileng ka liphetoho tse ling23,64. Taba ea pele, 30 mmol Zn(NO3)2·6H2O (8.925 g) le 3.5 mmol Co(NO3)2·6H2O (1.014 g) li ile tsa kopanngoa 'me tsa qhibiliha ka har'a 300 ml ea methanol. Eaba, 120 mmol ea 2-methylimidazole (9.853 g) e qhibilihisoa ka har'a 100 ml ea methanol 'me ea eketsoa tharollong e ka holimo. Motsoako o ile oa hlohlelletsoa mochesong oa kamore ka lihora tse 24. Qetellong, sehlahisoa se ile sa aroloa ka ho centrifugation ho 6429 g metsotso e 10 'me sa hlatsuoa hantle ka methanol ka makhetlo a mararo. Phofo e hlahisitsoeng e ile ea omisoa ka har'a vacuum ho 60°C bosiu bohle pele e sebelisoa.
Ho kopanya Co-SAs/NPs@NC-950, phofo e omileng ea CoZn-ZIF e ile ea chesoa ka pyrolysis ho 950 °C ka hora e le 'ngoe phallong ea khase ea 6% H2 + 94% Ar, ka sekhahla sa ho futhumatsa sa 5 °C/min. Sampole e ile ea pholisoa mochesong oa kamore ho fumana Co-SA/NPs@NC-950. Bakeng sa Co-SAs/NPs@NC-850 kapa Co-SAs/NPs@NC-750, mocheso oa pyrolysis o ile oa fetoloa ho 850 le 750 °C, ka ho latellana. Lisampole tse lokisitsoeng li ka sebelisoa ntle le ts'ebetso e 'ngoe, joalo ka ho qoelisoa ha asiti.
Litekanyo tsa TEM (transmission electron microscopy) li entsoe ho microscope ea Thermo Fisher Titan Themis 60-300 "cube" e nang le aberration corrector bakeng sa ho nka litšoantšo le lense ea ho bopa probe ea 300 kV. Liteko tsa HAADF-STEM li entsoe ho sebelisoa microscope ea FEI Titan G2 le FEI Titan Themis Z e nang le li-probe le li-photo corrector, hammoho le li-detector tsa likarolo tse 'ne tsa DF4. Litšoantšo tsa 'mapa oa likarolo tsa EDS le tsona li fumanoe ho microscope ea FEI Titan Themis Z. Tlhahlobo ea XPS e entsoe ho spectrometer ea photoelectron ea X-ray (Thermo Fisher model ESCALAB 250Xi). XANES le EXAFS spectra ea Co K-edge li ile tsa bokelloa ho sebelisoa tafole ea XAFS-500 (China Spectral Instruments Co., Ltd.). Bokahare ba Co bo ile ba khethoa ke atom absorption spectroscopy (AAS) (PinAAcle900T). Di-spectra tsa diffraction tsa X-ray (XRD) di rekotilwe ho diffractometer ya X-ray (Bruker, Bruker D8 Advance, Jeremane). Di-isotherm tsa adsorption ya naetrojene di fumanwe ho sebediswa sesebediswa sa adsorption sa mmele (Micromeritics, ASAP2020, USA).
Karabelo ea ho tlosoa ha hydrogen e entsoe sepakapakeng sa argon moo moea o tlosoang ho latela mokhoa o tloaelehileng oa Schlenk. Sejana sa karabelo se ile sa ntšoa 'me sa tlatsoa ka argon ka makhetlo a 6. Bulela phepelo ea metsi a condenser 'me u kenye catalyst (30 mg) le solvent (6 ml). Chesa setshelo mochesong o lakatsehang u sebelisa thermostat 'me u se lumelle ho lekana metsotso e 30. Asiti ea formic (10 mmol, 377 μL) e ile ea eketsoa sejaneng sa karabelo tlas'a argon. Reteletsa valve ea burette ea mahlakore a mararo ho theola khatello ea reactor, u e koale hape, 'me u qale ho lekanya bophahamo ba khase e hlahisoang u sebelisa burette ea letsoho (Setšoantšo sa S16). Kamora nako e hlokahalang hore karabelo e phethehe, sampole ea khase e ile ea bokelloa bakeng sa tlhahlobo ea GC ho sebelisoa syringe e sa keneng khase e hloekisitsoeng ka argon.
Liteko tsa ho phaphamala ha sebaka li entsoe ho spectrometer ea Fourier transform infrared (FTIR) (Thermo Fisher Scientific, Nicolet iS50) e nang le detector ea mercury cadmium telluride (MCT). Phofo ea catalyst e ile ea kenngoa ka seleng ea karabelo (Harrick Scientific Products, Praying Mantis). Kamora ho phekola catalyst ka molapo oa Ar (50 ml/min) mochesong oa kamore, sampole e ile ea futhumatsoa mochesong o fanoeng, ebe e tšeloa ka Ar (50 ml/min) ka har'a tharollo ea HCOOH 'me ea tšeloa ka har'a sele ea karabelo ea in-situ. bakeng sa karabelo. Mekhoa ea mohlala ea catalytic e fapaneng. Li-spectra tsa infrared li ile tsa tlalehoa ka linako tse fapaneng ho tloha metsotsoana e 3.0 ho isa ho hora e le 'ngoe.
HCOOH, DCOOH, HCOOD le DCOOD li sebelisoa e le li-substrate ka har'a propylene carbonate. Maemo a setseng a tsamaellana le ts'ebetso ea ho tlosoa ha HCOOH ke oksijene.
Lipalo tsa melao-motheo ea pele li entsoe ho sebelisoa moralo oa khopolo-taba ea ts'ebetso ea density ka har'a sephutheloana sa mohlala sa Vienna Ab initio (VASP 5.4.4) 65,66. Sele ea superunit e nang le bokaholimo ba graphene (5 × 5) e nang le tekanyo e ka bang 12.5 Å e sebelisitsoe e le substrate bakeng sa CoN2C2 le CoN2C2-Co6. Sebaka sa vacuum se fetang 15 Å se ile sa eketsoa ho qoba tšebelisano lipakeng tsa mekhahlelo e haufi ea substrate. Tšebelisano lipakeng tsa li-ion le lielektrone e hlalosoa ke mokhoa o boletsoeng oa amplified wave (PAW)65,67. Mosebetsi oa Perdue-Burke-Ernzerhoff (PBE) generalized gradient approximation (GGA) o hlahisitsoeng ke Grimm ka van der Waals correction68,69 o ile oa sebelisoa. Litekanyetso tsa convergence bakeng sa matla le matla a felletseng ke 10−6 eV/atom le 0.01 eV/Å. Khaotso ea matla e behiloe ho 600 eV ho sebelisoa gridi ea Monkhorst-Pack 2 × 2 × 1 K-point. Potlako e sa tloaelehang e sebelisitsoeng mohlaleng ona e hahiloe ho tloha sebopehong sa elektroniki ho ea boemong ba C 2s22p2, boemo ba N 2s22p3, boemo ba Co 3d74s2, boemo ba H 1 s1, le boemo ba O 2s22p4. Phapang ea matla a adsorption le density ea electron e baloa ka ho tlosa matla a karolo ea khase le mefuta ea bokaholimo ho tsoa matla a sistimi e adsorbed ho latela mehlala ea adsorption kapa interface70,71,72,73,74. Tokiso ea matla a mahala a Gibbs e sebelisoa ho fetolela matla a DFT hore e be matla a mahala a Gibbs 'me e ela hloko menehelo ea vibrational ho entropy le zero point energy75. Mokhoa oa ascending image-nudging elastic band (CI-NEB) o sebelisitsoe ho batla boemo ba phetoho ea karabelo76.
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