Enkosi ngokutyelela iNature.com. Inguqulelo yesikhangeli osisebenzisayo inenkxaso encinci yeCSS. Ukuze ufumane iziphumo ezilungileyo, sicebisa ukuba usebenzise inguqulelo entsha yesikhangeli sakho (okanye uvale iMowudi yoKuhambelana kwi-Internet Explorer). Okwangoku, ukuqinisekisa inkxaso eqhubekayo, sibonisa indawo ngaphandle kwesitayile okanye iJavaScript.
Uphuhliso lwetekhnoloji ye-hydrogen lusembindini woqoqosho oluluhlaza. Njengemfuneko yokufezekisa ukugcinwa kwe-hydrogen, kufuneka ii-catalysts ezisebenzayo nezizinzileyo ze-hydrogenation (de)hydrogenation reaction. Ukuza kuthi ga ngoku, le ndawo ilawulwa kukusetyenziswa kweentsimbi ezixabisekileyo ezibizayo. Apha, sicebisa i-catalyst entsha esekwe kwi-cobalt exabiso liphantsi (Co-SAs/NPs@NC) apho iindawo zesinyithi esinye ezisasazeke kakhulu zidityaniswe ngokudibeneyo nee-nanoparticles ezintle ukuze kufezekiswe i-formic acid dehydrogenation esebenzayo. Ukusebenzisa izinto ezilungileyo zeeyunithi ze-CoN2C2 ezisasazeke ngeathomu kunye nee-nanoparticles ezifakwe kwii-7-8 nm, kusetyenziswa i-propylene carbonate njenge-solvent, kwafunyanwa imveliso yegesi egqwesileyo ye-1403.8 ml g-1 h-1, kwaye akukho lahleko emva kwemijikelo emi-5. umsebenzi, ongcono ngokuphindwe ka-15 kune-Pd/C yorhwebo. Uvavanyo lwe-In situ lubonisa ukuba, xa kuthelekiswa ne-single metal atom kunye ne-nanoparticle catalysts ezinxulumeneyo, i-Co-SAs/NPs@NC iphucula ukutsalwa kunye nokusebenza kwe-key monodentate intermediate HCOO*, ngaloo ndlela ikhuthaza ukuqhekeka kwe-CH bond okulandelayo. Ubalo lwethiyori lubonisa ukuba ukuhlanganiswa kwe-cobalt nanoparticles kukhuthaza ukuguqulwa kweziko le-d-band le-atom enye ye-Co ibe yindawo esebenzayo, ngaloo ndlela kuphucula ukudibana phakathi kwe-carbonyl O ye-HCOO* intermediate kunye neziko le-Co, ngaloo ndlela kunciphisa umqobo wamandla.
I-Hydrogen ithathwa njengomthwali wamandla obalulekileyo kutshintsho lwamandla lwehlabathi lwangoku kwaye inokuba ngumqhubi ophambili wokufikelela kwi-carbon neutral1. Ngenxa yeempawu zayo zomzimba ezifana nokutsha kunye noxinano oluphantsi, ukugcinwa okukhuselekileyo nokusebenzayo kunye nokuthuthwa kwe-hydrogen yimiba ephambili ekufezekiseni uqoqosho lwe-hydrogen2,3,4. Ii-hydrogen carriers ezingamanzi eziphilayo (ii-LOHC), ezigcina kwaye zikhuphe i-hydrogen ngeempendulo zeekhemikhali, ziye zacetyiswa njengesisombululo. Xa kuthelekiswa ne-hydrogen yemolekyuli, izinto ezinjalo (i-methanol, i-toluene, i-dibenzyltoluene, njl.njl.) kulula kwaye kulula ukuziphatha5,6,7. Phakathi kwee-LOHC ezahlukeneyo zemveli, i-formic acid (i-FA) inetyhefu ephantsi (LD50: 1.8 g/kg) kunye nomthamo we-H2 we-53 g/L okanye i-4.4 wt%. Okuphawulekayo kukuba, i-FA yeyona LOHC kuphela enokugcina kwaye ikhuphe i-hydrogen phantsi kweemeko ezithambileyo xa kukho ii-catalysts ezifanelekileyo, ngaloo ndlela ayifuni igalelo elikhulu lamandla angaphandle1,8,9. Enyanisweni, kuye kwaveliswa ii-noble metal catalysts ezininzi zokunciphisa i-hydrogenation ye-formic acid, umzekelo, ii-catalysts ezisekelwe kwi-palladium zisebenza ngokuphindwe ka-50-200 kunee-catalysts zesinyithi ezingabizi kakhulu10,11,12. Nangona kunjalo, ukuba ucinga ngexabiso lee-active metals, umzekelo, i-palladium ibiza ngaphezu kwe-1000 amaxesha.
ICobalt, Ukukhangela ii-catalysts zesinyithi ezisisiseko ezisebenzayo nezizinzileyo kuyaqhubeka nokutsala umdla wabaphandi abaninzi kwezemfundo nakwishishini13,14,15.
Nangona ii-catalysts ezingabizi kakhulu ezisekelwe kwi-Mo kunye ne-Co, kunye nee-nanocatalysts ezenziwe ngee-alloys ze-noble/base metal, 14,16 ziye zaphuhliswa ukuze kususwe i-FA, ukucima kwazo kancinci ngexesha lokusabela akunakuphepheka ngenxa yokuhlala kwiindawo ezisebenzayo zeemetals, i-CO2, kunye ne-H2O ziiprotons. okanye ii-anions ze-formate (HCOO-), ungcoliseko lwe-FA, ukuhlanganiswa kwamasuntswana kunye nokutyhefa kwe-CO17,18. Thina nabanye kutshanje sibonise ukuba ii-catalysts ze-atom enye (ii-SAC) ezineendawo ze-CoIINx ezisasazeke kakhulu njengeendawo ezisebenzayo ziphucula ukusabela kunye nokumelana ne-asidi ye-formic acid dehydrogenation xa kuthelekiswa ne-nanoparticles17,19,20,21,22,23,24. Kwezi zinto ze-Co-NC, ii-athomu ze-N zisebenza njengeendawo eziphambili zokukhuthaza ukususwa kwe-FA ngelixa ziphucula uzinzo lwesakhiwo ngokudibanisa ne-athomu ye-Co ephakathi, ngelixa ii-athomu ze-Co zibonelela ngeendawo ze-H adsorption kwaye zikhuthaza i-CH22 scission, 25,26. Ngelishwa, umsebenzi kunye nozinzo lwezi catalysts zisekude kakhulu kwii catalysts zesinyithi ezidumileyo nezingafaniyo zanamhlanje (Umzobo 1) 13.
Amandla agqithisileyo avela kwimithombo evuselelekayo efana nelanga okanye umoya anokuveliswa yi-electrolysis yamanzi. I-hydrogen eveliswayo inokugcinwa kusetyenziswa i-LOHC, ulwelo olune-hydrogenation kunye ne-dehydrogenation ezinokuthi ziguqulwe. Kwinyathelo lokuphelelwa yi-hydrogen, imveliso ekuphela kwayo yi-hydrogen, kwaye ulwelo oluthwalayo lubuyiselwa kwimeko yalo yokuqala kwaye lufakwe i-hydrogen kwakhona. I-Hydrogen ekugqibeleni inokusetyenziswa kwizikhululo zepetroli, iibhetri, izakhiwo zoshishino, nokunye.
Kutshanje, kuye kwaxelwa ukuba umsebenzi wangaphakathi wee-SAC ezithile unokwandiswa xa kukho ii-athomu zesinyithi ezahlukeneyo okanye ezinye iindawo zesinyithi ezibonelelwa zii-nanoparticles (NPs) okanye ii-nanoclusters (NCs)27,28. Oku kuvula amathuba okufunxa ngakumbi kunye nokusebenza kwe-substrate, kunye nokuguqulwa kwejometri kunye nesakhiwo se-elektroniki seendawo ze-monatomic. Ke ngoko, ukufunxa/ukuvuselela i-substrate kunokulungiswa, okubonelela ngokusebenza ngcono kwe-catalytic29,30. Oku kusinika umbono wokudala izinto ezifanelekileyo ze-catalytic ezineendawo ezisebenzayo ze-hybrid. Nangona ii-SAC eziphuculweyo zibonakalise amandla amakhulu kuluhlu olubanzi lwezicelo ze-catalytic, indima yazo ekugcinweni kwe-hydrogen, ngolwazi lwethu, ayicacanga. Kule nkalo, sibika icebo eliguquguqukayo neliqinileyo lokwenziwa kwee-catalysts ze-hybrid ezisekelwe kwi-cobalt (Co-SAs/NPs@NCs) eziquka ii-nanoparticles ezichaziweyo kunye namaziko esinyithi ngamanye. IiCo-SAs/NPs@NC ezilungisiweyo zibonisa ukusebenza kakuhle kwe-formic acid dehydrogenation, okungcono kunee-catalysts ezingezizo ezibalaseleyo (ezifana neCoNx, ii-atom ze-cobalt ezingatshatanga, i-cobalt@NC kunye ne-γ-Mo2N) kunye nee-catalysts zesinyithi ezihloniphekileyo. Ukuchazwa kwendawo kunye nokubalwa kwe-DFT kwee-catalysts ezisebenzayo kubonisa ukuba iindawo zesinyithi ngazinye zisebenza njengeendawo ezisebenzayo, kwaye ii-nanoparticles zale nto intsha ziphucula iziko le-d-band yee-atom zeCo, zikhuthaza ukufunxwa kunye nokusebenza kwe-HCOO*, ngaloo ndlela zinciphisa umqobo wamandla wempendulo.
Ii-Zeolite imidazolate frameworks (ZIFs) zizinto ezichazwe kakuhle ezi-three-dimensional precursors ezibonelela ngee-catalysts zezinto ze-carbonaceous ezifakwe i-nitrogen (ii-catalysts ze-metal-NC) ukuxhasa iintlobo ezahlukeneyo zeesinyithi37,38. Ke ngoko, i-Co(NO3)2 kunye ne-Zn(NO3)2 zidityaniswe ne-2-methylimidazole kwi-methanol ukwenza ii-complexes zesinyithi ezihambelanayo kwisisombululo. Emva kokufakwa kwe-centrifugation kunye nokomisa, i-CoZn-ZIF yatshiswa ngamaqondo obushushu ahlukeneyo (750–950 °C) kwi-atmospheric ye-6% H2 kunye ne-94% Ar. Njengoko kubonisiwe kumfanekiso ongezantsi, izinto eziveliswayo zineempawu ezahlukeneyo zesiza esisebenzayo kwaye zibizwa ngokuba yi-Co-SAs/NPs@NC-950, i-Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750 (Umfanekiso 2a). ). Ukuqwalaselwa okukhethekileyo kovavanyo lwamanyathelo athile abalulekileyo kwinkqubo yokwenza izinto kuchazwe kwiMifanekiso 1 kunye ne-2. C1-C3. I-variable temperature powder X-ray diffraction (VTXRD) yenziwe ukujonga ukuguquka kwe-catalyst. Emva kokuba ubushushu be-pyrolysis bufikelele kwi-650 °C, ipatheni ye-XRD itshintsha kakhulu ngenxa yokuwa kwesakhiwo sekristale esicwangcisiweyo se-ZIF (Umzobo S4) 39. Njengoko ubushushu busanda ngakumbi, kuvela iincopho ezimbini ezibanzi kwiipatheni ze-XRD ze-Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750 kwi-20–30° kunye ne-40–50°, ezimele incopho ye-amorphous carbon (Umzobo C5). 40. Kubalulekile ukuqaphela ukuba ziincopho ezintathu kuphela eziphawulweyo ezibonwe kwi-44.2°, 51.5° kunye ne-75.8°, ezizeze-metallic cobalt (JCPDS #15-0806), kunye ne-26.2°, ezizeze-graphitic carbon (JCPDS # 41-1487). I-X-ray spectrum ye-Co-SAs/NPs@NC-950 ibonisa ubukho be-graphite-like encapsulated cobalt nanoparticles kwi-catalyst41,42,43,44. I-Raman spectrum ibonisa ukuba i-Co-SAs/NPs@NC-950 ibonakala ineencochoyi ze-D kunye ne-G eziqinileyo nezincinci kunezinye iisampuli, nto leyo ebonisa inqanaba eliphezulu le-graphitization (Umfanekiso S6). Ukongeza, i-Co-SAs/NPs@NC-950 ibonisa indawo ephezulu ye-Brunner-Emmett-Taylor (BET) kunye nomthamo we-pore (1261 m2 g-1 kunye ne-0.37 cm3 g-1) kunezinye iisampuli kwaye uninzi lwee-ZIF zizinto ze-NC derivatives. (Umfanekiso S7 kunye neTheyibhile S1). I-Atomic absorption spectroscopy (AAS) ibonisa ukuba umxholo we-cobalt we-Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@ yi-2.69 wt%, 2.74 % wt. kunye ne-2.73% wt. NC-750 ngokwahlukeneyo (Itheyibhile S2). Umxholo we-Zn we-Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750 uyanda kancinci kancinci, nto leyo ebangelwa kukwehla okunyukileyo kunye nokuguquguquka kweeyunithi ze-Zn. Ukunyuka kobushushu be-pyrolysis (Zn, iqondo lokubila = 907 °C) 45.46. Uhlalutyo lwe-elemental (EA) lubonise ukuba ipesenti ye-N iyancipha ngobushushu be-pyrolysis obukhulayo, kwaye umxholo ophezulu we-O unokubangelwa kukufakwa kwe-molecular O2 ukusuka ekuchatshazelweni ngumoya. (Itheyibhile S3). Kwi-cobalt ethile equlathekileyo, ii-nanoparticles kunye nee-coatom ezizimeleyo zihlala kunye, nto leyo ebangela ukwanda okukhulu komsebenzi we-catalyst, njengoko kuxoxwe ngezantsi.
Umzobo weskematiki wokwenziwa kweCo-SA/NPs@NC-T, apho uT bubushushu be-pyrolysis (°C). b umfanekiso weTEM. c Umfanekiso weCo-SAs/NPs@NC-950 AC-HAADF-STEM. Iiathom zeCo nganye ziphawulwe ngezangqa ezibomvu. d Itemplate ye-EDS Co-SA/NPs@NC-950.
Okuphawulekayo kukuba, i-transmission electron microscopy (TEM) ibonise ubukho bee-cobalt nanoparticles (NPs) ezahlukeneyo ezinobukhulu obuphakathi be-7.5 ± 1.7 nm kuphela kwi-Co-SA/NPs@NC-950 (Imifanekiso 2 b kunye ne-S8). Ezi nanoparticles zifakwe kwi-graphite-like carbon efakwe i-nitrogen. I-lattice fringe spacing ye-0.361 kunye ne-0.201 nm ihambelana ne-graphitic carbon (002) kunye ne-metallic Co (111) particles, ngokulandelelana. Ukongeza, i-high-angle aberration-corrected annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) ityhile ukuba ii-Co NPs kwi-Co-SAs/NPs@NC-950 zazijikelezwe yi-atomic cobalt eninzi (Umzobo 2c). Nangona kunjalo, ii-atoms ze-cobalt ezisasazeke ngeatom kuphela ezibonwe kwinkxaso yezinye iisampuli ezimbini (Umzobo S9). Umfanekiso we-Energy dispersive spectroscopy (EDS) HAADF-STEM ubonisa ukusasazwa okufanayo kwe-C, N, Co kunye ne-Co NPs ezahlulwe ngokwee-Co kwi-Co-SAs/NPs@NC-950 (Umzobo 2d). Zonke ezi ziphumo zibonisa ukuba amaziko e-Co asasazeke ngokwee-atom kunye ne-nanoparticles ezifakwe kwi-carbon efana ne-graphite efakwe i-N zincamathiselwe ngempumelelo kwi-NC substrates kwi-Co-SAs/NPs@NC-950, ngelixa amaziko esinyithi ahlukeneyo kuphela.
Imeko ye-valence kunye nokwakheka kweekhemikhali kwezinto ezifunyenweyo kufundwe yi-X-ray photoelectron spectroscopy (XPS). I-XPS spectra yee-catalysts ezintathu ibonise ubukho bezinto ze-Co, N, C kunye ne-O, kodwa i-Zn yayikhona kuphela kwi-Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750 (Umzobo 2). ). C10). Njengoko ubushushu be-pyrolysis busanda, umxholo we-nitrogen uwonke uyancipha njengoko iintlobo ze-nitrogen zingazinzi kwaye zibola zibe ziigesi ze-NH3 kunye ne-NOx kumaqondo obushushu aphezulu (Itheyibhile S4) 47. Ngoko ke, umxholo wekhabhoni uwonke unyuke kancinci ukusuka kwi-Co-SAs/NPs@NC-750 ukuya kwi-Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-950 (Imifanekiso S11 kunye ne-S12). Isampuli efakwe kwi-pyrolyzed kumaqondo obushushu aphezulu inenxalenye ephantsi yee-athomu ze-nitrogen, oko kuthetha ukuba inani lee-NC carriers kwi-Co-SAs/NPs@NC-950 kufuneka libe ngaphantsi kunezinye iisampuli. Oku kukhokelela ekutshiseni ngamandla kwamasuntswana e-cobalt. I-spectrum ye-O1s ibonisa iincopho ezimbini ze-C=O (531.6 eV) kunye ne-C–O (533.5 eV), ngokulandelelana (Umfanekiso S13) 48. Njengoko kubonisiwe kuMfanekiso 2a, i-spectrum ye-N1s inokusonjululwa ibe ziincopho ezine ze-pyridine nitrogen N (398.4 eV), i-pyrrole N (401.1 eV), i-graphite N (402.3 eV) kunye ne-Co-N (399.2 eV). Iibhondi ze-Co-N zikhona kuzo zonke iisampulu ezintathu, nto leyo ebonisa ukuba ezinye ii-athomu ze-N zilungelelaniswe kwiindawo ze-monometallic, kodwa iimpawu zahlukile kakhulu49. Ukusetyenziswa kobushushu obuphezulu be-pyrolysis kunokunciphisa kakhulu umxholo weentlobo ze-Co-N ukusuka kwi-43.7% kwi-Co-SA/NPs@NC-750 ukuya kwi-27.0% kwi-Co-SAs/NPs@NC-850 kunye ne-Co 17.6%@ NC-950. kwi--CA/NPs, ehambelana nokwanda komxholo we-C (Umzobo 3a), okubonisa ukuba inani labo lokudibanisa i-Co-N linokutshintsha kwaye lithatyathelwe indawo yi-athomu ze-C50. I-spectrum ye-Zn 2p ibonisa ukuba le nto ikhona ikakhulu kwimo ye-Zn2+. (Umfanekiso S14) 51. I-spectrum ye-Co 2p ibonisa iincopho ezimbini ezibalaseleyo kwi-780.8 kunye ne-796.1 eV, ezibangelwa yi-Co 2p3/2 kunye ne-Co 2p1/2, ngokulandelelana (Umfanekiso 3b). Xa kuthelekiswa ne-Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750, incopho ye-Co-N kwi-Co-SAs/NPs@NC-950 itshintshelwa kwicala elihle, okubonisa ukuba i-athomu enye ye-Co kumphezulu we--SAs/NPs@NC-950 inomlinganiselo ophezulu wokuphelelwa yi-electron, okubangela imeko ephezulu ye-oxidation. Kubalulekile ukuqaphela ukuba yiCo-SAs/NPs@NC-950 kuphela ebonise incopho ebuthathaka ye-zero-valent cobalt (Co0) kwi-778.5 eV, nto leyo ebonisa ukuba kukho ii-nanoparticles ezibangelwa kukuhlanganiswa kwe-cobalt SA kumaqondo obushushu aphezulu.
a N 1s kunye b Co 2p spectra ye Co-SA/NPs@NC-T. c XANES kunye d FT-EXAFS spectra ye Co-K-edge ye Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 kunye Co-SAs/NPs@NC-750. e WT-EXAFS contour plots ye Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850, kunye Co-SAs/NPs@NC-750. f FT-EXAFS fitting curve ye Co-SA/NPs@NC-950.
I-X-ray absorption spectroscopy (XAS) evalwe ngexesha (time-locked X-ray absorption spectrum) yasetyenziswa ukuhlalutya isakhiwo se-elektroniki kunye nendawo yokudibanisa yeentlobo ze-Co kwisampulu elungisiweyo. I-Cobalt valence states kwi-Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750. Isakhiwo se-Edge sityhilwe yi-normalized near-field X-ray absorption ye-Co-K edge (XANES) spectrum. Njengoko kubonisiwe kuMfanekiso 3c, ukufunxwa kufutshane nomphetho weesampuli ezintathu kuphakathi kwe-Co kunye ne-CoO foils, okubonisa ukuba imeko ye-valence yeentlobo ze-Co isusela kwi-0 ukuya kwi-+253. Ukongeza, utshintsho oluya kumandla aphantsi lubonwe ukusuka kwi-Co-SAs/NPs@NC-950 ukuya kwi-Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750, okubonisa ukuba i-Co-SAs/NPs@NC-750 ine-reverse order esezantsi. Ngokweziphumo zokudibanisa okucwangcisiweyo, imeko ye-Co valence ye-Co-SAs/NPs@NC-950 iqikelelwa ukuba yi-+0.642, ephantsi kunemeko ye-Co valence ye-Co-SAs/NPs@NC-850 (+1.376). Co-SA/NP @NC-750 (+1.402). Ezi ziphumo zibonisa ukuba imeko ye-oxidation ephakathi yee-cobalt particles kwi-Co-SAs/NPs@NC-950 inciphile kakhulu, nto leyo ehambelana neziphumo ze-XRD kunye ne-HADF-STEM kwaye inokuchazwa kukubakho kwee-cobalt nanoparticles kunye ne-single cobalt. Iiathom zeCo 41. I-Fourier transform X-ray absorption fine structure (FT-EXAFS) spectrum yeCo K-edge ibonisa ukuba incochoyi ephambili kwi-1.32 Å yeyeshell yeCo-N/Co-C, ngelixa indlela yokusasazeka kweCo-Co yentsimbi ikwi-2.18 kuphela kwiCo-SAs Å efumaneka kwi-/NPs@NC-950 (Umzobo 3d). Ngaphezu koko, i-wavelet transform (WT) contour plot ibonisa i-maximum intensity kwi-6.7 Å-1 ebangelwa yiCo-N/Co-C, ngelixa yiCo-SAs/NPs@NC-950 kuphela ebonisa i-maximum intensity ebangelwa yi-8.8. Enye i-intensity maximum ikwi-Å−1 kwi-Co-Co bond (Umzobo 3e). Ukongeza, uhlalutyo lwe-EXAFS olwenziwe ngumqeshi lubonise ukuba kumaqondo obushushu e-pyrolysis angama-750, 850 kunye nama-950 °C, amanani oqhagamshelwano lwe-Co-N ayengama-3.8, 3.2 kunye nama-2.3, ngokulandelanayo, kwaye amanani oqhagamshelwano lwe-Co-C ayengama-0. 0.9 kunye no-1.8 (Umzobo 3f, S15 kunye neTheyibhile S1). Ngokukodwa, iziphumo zamva nje zinokubangelwa bubukho beeyunithi ze-CoN2C2 ezisasazeke ngeathomu kunye nee-nanoparticles kwi-Co-SAs/NPs@NC-950. Ngokwahlukileyo koko, kwi-Co-SAs/NPs@NC-850 kunye ne-Co-SAs/NPs@NC-750, ziiyunithi ze-CoN3C kunye ne-CoN4 kuphela ezikhoyo. Kuyacaca ukuba ngobushushu be-pyrolysis obandayo, ii-athomu ze-N kwiyunithi ye-CoN4 zitshintshwa kancinci kancinci zii-athomu ze-C, kwaye i-cobalt CA ihlangana ukuze yenze ii-nanoparticles.
Iimeko zokusabela ezifundwe ngaphambili zazisetyenziselwa ukufunda impembelelo yeemeko zokulungiselela kwiimpawu zezinto ezahlukeneyo (Umzobo S16)17,49. Njengoko kubonisiwe kuMfanekiso 4 a, umsebenzi weCo-SAs/NPs@NC-950 uphezulu kakhulu kunoweCo-SAs/NPs@NC-850 kunye neCo-SAs/NPs@NC-750. Okuphawulekayo kukuba, zonke iisampulu ezintathu zeCo ezilungisiweyo zibonise ukusebenza okuphezulu xa kuthelekiswa nee-catalysts zesinyithi ezixabisekileyo zorhwebo (Pd/C kunye nePt/C). Ukongeza, iisampulu zeZn-ZIF-8 kunye neZn-NC bezingasebenzi ekukhutshweni kwe-formic acid, nto leyo ebonisa ukuba amasuntswana eZn azikho kwiindawo ezisebenzayo, kodwa impembelelo yawo kumsebenzi ayinamsebenzi. Ukongeza, umsebenzi weCo-SAs/NPs@NC-850 kunye neCo-SAs/NPs@NC-750 wenze i-pyrolysis yesibini kwi-950°C kangangeyure e-1, kodwa wawungaphantsi kunoweCo-SAs/NPs@NC-750. @NC-950 (Umzobo S17). Ukuchazwa kwesakhiwo kwezi zinto kubonise ubukho bee-nanoparticles ze-Co kwiisampuli eziphinde zaphikiswa, kodwa indawo ephantsi ethile kunye nokungabikho kwe-carbon efana ne-graphite kubangele umsebenzi ophantsi xa kuthelekiswa ne-Co-SAs/NPs@NC-950 (Umfanekiso S18–S20). Umsebenzi weesampuli ezineemilinganiselo ezahlukeneyo ze-Co precursor nawo uthelekiswe, kunye nomsebenzi ophezulu oboniswe kwi-3.5 mol addition (Itheyibhile S6 kunye noMfanekiso S21). Kuyacaca ukuba ukwakheka kwamaziko esinyithi ahlukeneyo kuchaphazeleka ngumxholo we-hydrogen kwi-pyrolysis atmosphere kunye nexesha le-pyrolysis. Ke ngoko, ezinye izinto ze-Co-SAs/NPs@NC-950 zivavanywe ngomsebenzi we-formic acid dehydrogenation. Zonke izinto zibonise ukusebenza okuphakathi ukuya kokulungileyo kakhulu; nangona kunjalo, akukho nanye kuzo eyayingcono kune-Co-SAs/NPs@NC-950 (Imifanekiso S22 kunye ne-S23). Ukuchazwa kwesakhiwo sezinto kubonise ukuba ngexesha le-pyrolysis elonyukayo, umxholo wezikhundla ze-monoatomic Co-N uyancipha kancinci kancinci ngenxa yokuhlanganiswa kwee-athomu zesinyithi zibe zii-nanoparticles, nto leyo echaza umahluko kumsebenzi phakathi kweesampuli ezinexesha le-pyrolysis eliyi-100-2000. umahluko yi-0.5 h, i-1 h, kunye ne-2 h (Imifanekiso S24–S28 kunye neTheyibhile S7).
Igrafu yomthamo wegesi xa kuthelekiswa nexesha elifunyenwe ngexesha lokususwa kwe-hydrogen kwi-fuel assemblies kusetyenziswa ii-catalysts ezahlukeneyo. Iimeko zokusabela: FA (10 mmol, 377 μl), catalyst (30 mg), PC (6 ml), Tback: 110 °C, Tactical: 98 °C, 4 parts b Co-SAs/NPs@NC-950 (30 mg), ii-solvents ezahlukeneyo. c Uthelekiso lwamazinga okuvela kwegesi kwii-catalysts ezahlukeneyo kwi-organic solvents kwi-85–110 °C. d Co-SA/NPs@NC-950 uvavanyo lokuphinda usebenzise. Iimeko zokusabela: FA (10 mmol, 377 µl), Co-SAs/NPs@NC-950 (30 mg), solvent (6 ml), Tback: 110 °C, Tactical: 98 °C, umjikelo ngamnye wokusabela uhlala iyure enye. Iibha zempazamo zimele ukuphambuka okuqhelekileyo okubalwe kwiimvavanyo ezintathu ezisebenzayo.
Ngokubanzi, ukusebenza kakuhle kwee-catalysts ze-FA dehydrogenation kuxhomekeke kakhulu kwiimeko zokusabela, ingakumbi i-solvent esetyenzisiweyo8,49. Xa kusetyenziswa amanzi njenge-solvent, i-Co-SAs/NPs@NC-950 ibonise izinga eliphezulu lokuqala lokusabela, kodwa kuye kwenzeka ukungasebenzi, mhlawumbi ngenxa yeeprotons okanye i-H2O18 ezihlala kwiindawo ezisebenzayo. Uvavanyo lwe-catalyst kwi-organic solvents ezifana ne-1,4-dioxane (DXA), i-n-butyl acetate (BAC), i-toluene (PhMe), i-triglyme kunye ne-cyclohexanone (CYC) nazo azibonisanga phuculo, nakwi-propylene carbonate (PC)) (Umzobo 4b kunye neTheyibhile S8). Ngokufanayo, izongezo ezifana ne-triethylamine (NEt3) okanye i-sodium formate (HCCONA) azizange zibe nefuthe elihle ngakumbi ekusebenzeni kwe-catalyst (Umfanekiso S29). Phantsi kweemeko ezifanelekileyo zokusabela, isivuno segesi sifikelele kwi-1403.8 mL g−1 h−1 (Umzobo S30), owawuphezulu kakhulu kunazo zonke ii-catalysts ze-Co ezixeliweyo ngaphambili (kuquka i-SAC17, 23, 24). Kwizilingo ezahlukeneyo, ngaphandle kweempendulo emanzini kunye nezongezo ze-formate, ukukhetha ukuya kuthi ga kwi-99.96% yokuphelelwa ngamanzi emzimbeni kunye nokuphelelwa ngamanzi emzimbeni kufunyenwe (Itheyibhile S9). Amandla okusebenza abaliweyo yi-88.4 kJ/mol, ethelekiswa namandla okusebenza kwee-catalysts zesinyithi ezihloniphekileyo (Umfanekiso S31 kunye neTheyibhile S10).
Ukongeza, sithelekise inani lezinye ii-catalysts ezahlukeneyo zokuphelelwa yi-asidi ye-formic phantsi kweemeko ezifanayo (Umzobo 4c, iitheyibhile S11 kunye ne-S12). Njengoko kubonisiwe kuMfanekiso 3c, izinga lokuveliswa kwegesi le-Co-SAs/NPs@NC-950 lidlula elo lee-catalysts zesinyithi ezisisiseko ezahlukeneyo ezaziwayo kwaye liphezulu ngokuphindwe ka-15 nange-15 kunele-5% Pd/C yorhwebo kunye ne-5% Pd/C, ngokulandelanayo. kanye. % Pt/C catalyst.
Uphawu olubalulekileyo lwalo naluphi na ukusetyenziswa okusebenzayo kwee-catalysts ze-hydrogenation (de) kukuzinza kwazo. Ke ngoko, uthotho lweemvavanyo zokuphinda zisetyenziswe kusetyenziswa i-Co-SAs/NPs@NC-950 lwenziwe. Njengoko kubonisiwe kuMfanekiso 4 d, umsebenzi wokuqala kunye nokukhetha kwezinto azizange zitshintshe kwimijikelo emihlanu elandelelanayo (jonga kwakhona iTheyibhile S13). Uvavanyo lwexesha elide lwenziwe kwaye imveliso yegesi yanda ngokuthe ngqo kwiiyure ezingama-72 (Umfanekiso S32). Umxholo we-cobalt we-Co-SA/NPs@NC-950 esetyenzisiweyo yayiyi-2.5 wt%, eyayisondele kakhulu kwe-catalyst entsha, nto leyo ebonisa ukuba akukho kutsalwa kwe-cobalt okucacileyo (Itheyibhile S14). Akukho tshintsho lucacileyo lombala okanye ukuhlanganiswa kwamasuntswana esinyithi okubonwe ngaphambi nasemva kwempendulo (Umfanekiso S33). I-AC-HAADF-STEM kunye ne-EDS yezinto ezisetyenzisiweyo kwiimvavanyo zexesha elide zibonise ukugcinwa kunye nokusasazeka okufanayo kweendawo zokusasazeka kwe-athomu kwaye akukho tshintsho lubalulekileyo lwesakhiwo (Imifanekiso S34 kunye ne-S35). Iincopho zeCo0 kunye neCo-N zisekhona kwiXPS, nto leyo ebonisa ukuba kukho i-Co NPs kunye neendawo zesinyithi ezahlukeneyo, nto leyo eqinisekisa uzinzo lwe-Co-SAs/NPs@NC-950 catalyst (Umfanekiso S36).
Ukuchonga iindawo ezisebenzayo kakhulu ezinoxanduva lokuphelelwa yi-asidi ye-formic, izinto ezikhethiweyo ezineziko elinye lesinyithi (i-CoN2C2) okanye i-Co NP zalungiswa ngokusekelwe kwizifundo zangaphambili17. Ulandelelwano lomsebenzi wokuphelelwa yi-asidi ye-formic olubonwe phantsi kweemeko ezifanayo yi-Co-SAs/NPs@NC-950 > Co SA > Co NP (Itheyibhile S15), ebonisa ukuba iindawo ze-CoN2C2 ezisasazeke ngeathomu zisebenza ngakumbi kune-NPs. I-kinetics yokusabela ibonisa ukuba ukuvela kwe-hydrogen kulandela i-kinetics yokusabela kwe-first-order, kodwa imiqolomba yee-curves ezininzi kwi-cobalt content eyahlukileyo ayifani, ebonisa ukuba i-kinetics ayixhomekekanga kwi-asidi ye-formic kuphela, kodwa nakwindawo esebenzayo (Umzobo 2). C37). Izifundo ezongezelelweyo ze-kinetic zibonise ukuba, ngenxa yokungabikho kweencopho ze-cobalt metal kuhlalutyo lwe-X-ray diffraction, ulandelelwano lwe-kinetic lwempendulo ngokwemixholo ye-cobalt lufunyenwe luyi-1.02 kumanqanaba aphantsi (ngaphantsi kwe-2.5%), ebonisa ukusasazwa okuphantse kufane kweziko le-cobalt le-monoatomic. eziphambili. indawo esebenzayo (imizobo S38 kunye ne-S39). Xa umxholo wee-particles ze-Co ufikelela kwi-2.7%, i-r iyanda ngequbuliso, nto leyo ebonisa ukuba ii-nanoparticles zisebenzisana kakuhle nee-athomu zomntu ngamnye ukuze zenze umsebenzi ophezulu. Njengoko umxholo wee-particles ze-Co ukhula ngakumbi, i-curve iba yi-nonlinear, enxulunyaniswa nokwanda kwenani lee-nanoparticles kunye nokwehla kwezikhundla ze-monatomic. Ngoko ke, ukusebenza okuphuculweyo kwe-LC dehydrogenation ye-Co-SA/NPs@NC-950 kuvela kukuziphatha ngokubambisana kweendawo zesinyithi zomntu ngamnye kunye nee-nanoparticles.
Kwenziwe uphando olunzulu kusetyenziswa i-in situ diffuse reflectance Fourier transform (in situ DRIFT) ukuchonga ii-reaction intermediates kule nkqubo. Emva kokufudumeza iisampuli kumaqondo obushushu ahlukeneyo emva kokongeza i-formic acid, kwabonwa iiseti ezimbini zee-frequency (Umzobo 5a). Iincopho ezintathu ze-HCOOH* zivela kwi-1089, 1217 kunye ne-1790 cm-1, ezibangelwa kukungcangcazela kwe-out-of-plane CH π (CH) stretching vibration, CO ν (CO) stretching vibration kunye ne-C=O ν (C=O) stretching vibration, 54, 55 ngokulandelelana . Enye iseti yeencopho kwi-1363 kunye ne-1592 cm-1 ihambelana ne-symmetric OCO vibration νs(OCO) kunye ne-asymmetric OCO stretching vibration νas(OCO)33.56 HCOO*, ngokulandelelana. Njengoko i-reaction iqhubeka, iincopho ezinxulumene ne-HCOOH* kunye ne-HCOO* ziyancipha kancinci kancinci. Ngokubanzi, ukubola kwe-formic acid kubandakanya amanyathelo amathathu aphambili: (I) ukufunxwa kwe-formic acid kwiindawo ezisebenzayo, (II) ukususwa kwe-H ngendlela ye-formate okanye ye-carboxylate, kunye (III) ukudityaniswa kwe-H ezimbini ezifunxwayo ukuvelisa i-hydrogen. I-HCOO* kunye ne-COOH* zizinto eziphambili ekumiseleni iindlela ze-formate okanye ze-carboxylate, ngokulandelelana57. Kwinkqubo yethu ye-catalytic, kuphela i-HCOO* peak ephawulekayo evele, ebonisa ukuba ukubola kwe-formic acid kwenzeka kuphela ngendlela ye-formic acid58. Ukuqwalaselwa okufanayo kwenziwe kumaqondo obushushu aphantsi angama-78 °C kunye nama-88 °C (umzobo S40).
Iispectra ze-DRIFT ze-HCOOH dehydrogenation kwi-Co-SAs/NPs@NC-950 kunye ne-b Co SAs. Le ntsomi ibonisa amaxesha okusabela kwindawo. c Iintshukumo zomthamo wegesi ezifunyenwe kusetyenziswa ii-reagents ezahlukeneyo zokulebhelisha i-isotope. d Idatha yesiphumo se-Kinetic isotope.
Uvavanyo olufanayo lwe-DRIFT lwenziwe kwizinto ezinxulumene ne-Co NP kunye ne-Co SA ukuze kufundwe isiphumo sokusebenzisana kwi-Co-SA/NPs@NC-950 (Imifanekiso 5 b kunye ne-S41). Zombini izinto zibonisa iindlela ezifanayo, kodwa iincopho zeempawu ze-HCOOH* kunye ne-HCOO* zitshintshile kancinci, nto leyo ebonisa ukuba ukungeniswa kwe-Co NPs kutshintsha ulwakhiwo lwe-elektroniki lweziko le-monoatomic. Incopho yempawu ye-νas(OCO) ibonakala kwi-Co-SAs/NPs@NC-950 kunye ne-Co SA kodwa hayi kwi-Co NPs, nto leyo ebonisa ukuba i-intermediate eyenziwe xa kongezwa i-formic acid yi-monodentate formic acid ethe nkqo kumphezulu wetyuwa. kwaye ifakwa kwi-SA njengendawo esebenzayo 59. Kubalulekile ukuqaphela ukuba ukwanda okukhulu kokungcangcazela kweencopho zeempawu ze-π(CH) kunye ne-ν(C = O) kwabonwa, nto leyo ebonakala ikhokelele ekuguqulweni kwe-HCOOH* kwaye yenza kube lula ukuphendula. Ngenxa yoko, iincopho zeempawu ze-HCOOH* kunye ne-HCOO* kwi-Co-SAs/NPs@NC zaphantse zanyamalala emva kwemizuzu emi-2 yokusabela, okukhawulezayo kune-monometallic (imizuzu emi-6) kunye nee-nanoparticle-based catalysts (imizuzu eli-12). Zonke ezi ziphumo ziqinisekisa ukuba i-nanoparticle doping iphucula ukutsalwa kunye nokusebenza kwe-intermediates, ngaloo ndlela ikhawulezisa iimpendulo ezicetywayo apha ngasentla.
Ukuze kuhlalutywe ngakumbi indlela yokusabela kunye nokufumanisa inyathelo lokumisela izinga (RDS), isiphumo se-KIE senziwe phambi kwe-Co-SAs/NPs@NC-950. Apha, ii-isotopes ezahlukeneyo ze-formic acid ezifana ne-HCOOH, i-HCOOD, i-DCOOH kunye ne-DCOOD zisetyenziselwa izifundo ze-KIE. Njengoko kubonisiwe kuMfanekiso 5c, izinga lokuphelelwa ngamanzi emzimbeni liyancipha ngolu hlobo lulandelayo: i-HCOOH > i-HCOOD > i-DCOOH > i-DCOOD. Ukongeza, amaxabiso abaliweyo e-KHCOOH/KHCOOD, i-KHCOOH/KDCOOH, i-KHCOOD/KDCOOD kunye ne-KDCOOH/KDCOOD yayiyi-1.14, 1.71, 2.16 kunye ne-1.44, ngokulandelelana (Umzobo 5d). Ngoko ke, ukuqhekeka kwe-CH bond kwi-HCOO* kubonisa amaxabiso e-kH/kD ​​>1.5, okubonisa isiphumo esikhulu se-kinetic60,61, kwaye kubonakala ngathi kumela i-RDS ye-HCOOH dehydrogenation kwi-Co-SAs/NPs@NC-950.
Ukongeza, izibalo ze-DFT zenziwe ukuze kuqondwe impembelelo yee-nanoparticles ezifakwe kwi-doped kumsebenzi wangaphakathi we-Co-SA. Iimodeli ze-Co-SAs/NPs@NC kunye ne-Co-SA zakhiwe ngokusekelwe kuvavanyo olubonisiweyo kunye nemisebenzi yangaphambili (Iifig. 6a kunye ne-S42)52,62. Emva kokulungiswa kwejiyometri, ii-nanoparticles ezincinci ze-Co6 (CoN2C2) ezihlala kunye neeyunithi ze-monoatomic zachongwa, kwaye ubude be-bond ye-Co-C kunye ne-Co-N kwi-Co-SA/NPs@NC bachongwa ukuba yi-1.87 Å kunye ne-1.90 Å, ngokulandelanayo. , nto leyo ehambelana neziphumo ze-XAFS. I-calculated partial density of states (PDOS) ibonisa ukuba i-single Co metal atom kunye ne-nanoparticle composite (Co-SAs/NPs@NC) zibonisa i-hybridization ephezulu kufutshane nenqanaba le-Fermi xa kuthelekiswa ne-CoN2C2, nto leyo ebangela i-HCOOH. Ukudluliselwa kwe-electron ebolileyo kusebenza ngakumbi (Iifig. 6b kunye ne-S43). Amaziko e-d-band ahambelanayo e-Co-SAs/NPs@NC kunye ne-Co-SA abalwe njenge--0.67 eV kunye ne--0.80 eV, ngokulandelelana, phakathi kwawo ukwanda kwe-Co-SAs/NPs@NC kwakuyi-0.13 eV, nto leyo enegalelo lokuba emva kokungeniswa kwe-NP, ukutsalwa kwee-HCOO* particles yisakhiwo se-elektroniki esilungisiweyo se-CoN2C2 kwenzeka. Umahluko kubuninzi be-charge ubonisa ilifu elikhulu le-electron elijikeleze ibhloko ye-CoN2C2 kunye ne-nanoparticle, nto leyo ebonisa ukusebenzisana okunamandla phakathi kwazo ngenxa yokutshintshiselana kwe-electron. Idibene nohlalutyo lwe-Bader charge, kwafunyaniswa ukuba i-Co esasazeke ngeathomu ilahlekelwe yi-1.064e kwi-Co-SA/NPs@NC kunye ne-0.796e kwi-Co SA (Umfanekiso S44). Ezi ziphumo zibonisa ukuba ukuhlanganiswa kwee-nanoparticles kukhokelela ekunciphiseni kwe-electron kwiindawo ze-Co, okubangela ukwanda kwe-Co valence, okuhambelana neziphumo ze-XPS (Umzobo 6c). Iimpawu zokusebenzisana kwe-Co-O zokufakwa kwe-HCOO kwi-Co-SAs/NPs@NC kunye ne-Co SA zihlalutywe ngokubala iqela le-Hamiltonian eliyi-crystalline orbital (COHP)63. Njengoko kubonisiwe kuMfanekiso 6 d, amaxabiso angalunganga nalungileyo e--COHP ahambelana nesimo sokulwa nokubophelela kunye nesimo sokubophelela, ngokwahlukeneyo. Amandla ebhondi ye-Co-O afakwe yi-HCOO (Co-carbonylOH HCOO*) avavanywe ngokuhlanganisa amaxabiso e--COHP, awayeyi-3.51 kunye ne-3.38 kwi-Co-SAs/NPs@NC kunye ne-Co-SA, ngokwahlukeneyo. Ukusongelwa kwe-HCOOH kukwabonise iziphumo ezifanayo: ukunyuka kwexabiso elihlanganisiweyo le--COHP emva kokusetyenziswa kwe-nanoparticle kubonise ukwanda kwebhondi ye-Co-O, ngaloo ndlela kukhuthaza ukusebenza kwe-HCOO kunye ne-HCOOH (Umfanekiso S45).
Ulwakhiwo lweLattice lweCo-SA/NPs@NC-950. b PDOS Co-SA/NP@NC-950 kunye neCo SA. c I-isosurface ye-3D yomahluko kwiingxinano zetshaja ze-HCOOH adsorption kwiCo-SA/NPs@NC-950 kunye neCo-SA. (d) i-pCOHP yeebhondi zeCo-O ezifakwe yi-HCOO kwiCo-SA/NPs@NC-950 (ekhohlo) kunye neCo-SA (ekunene). e Indlela yokusabela ye-HCOOH dehydrogenation kwiCo-SA/NPs@NC-950 kunye neCo-SA.
Ukuze kuqondwe ngcono ukusebenza okuphezulu kokungabi namanzi emzimbeni kweCo-SA/NPs@NC, indlela yokusabela kunye namandla yasekwa. Ngokukodwa, ukungabi namanzi emzimbeni kwe-FA kubandakanya amanyathelo amahlanu, kuquka ukuguqulwa kwe-HCOOH ukuya kwi-HCOOH*, i-HCOOH* ukuya kwi-HCOO* + H*, i-HCOO* + H* ukuya kwi-2H* + CO2*, i-2H* + CO2* ukuya kwi-2H* + CO2, kunye ne-2H* kwi-H2 (Umzobo 6e). Amandla okufunxa iimolekyuli ze-formic acid kumphezulu we-catalyst nge-carbon oxygen aphantsi kune-hydroxyl oxygen (Imifanekiso S46 kunye ne-S47). Emva koko, ngenxa yamandla aphantsi, i-adsorbate ngokukhethekileyo idlula kwi-OH bond cleavage ukuze yenze i-HCOO* endaweni ye-CH bond cleavage ukuze yenze i-COOH*. Kwangaxeshanye, i-HCOO* isebenzisa i-monodentate adsorption, ekhuthaza ukuqhekeka kweebhondi kunye nokwakheka kwe-CO2 kunye ne-H2. Ezi ziphumo zihambelana nobukho bencopho ye-νas(OCO) kwi-in situ DRIFT, nto leyo ebonisa ukuba ukuchithwa kwe-FA kwenzeka ngendlela ye-formate kwisifundo sethu. Kubalulekile ukuqaphela ukuba ngokwemilinganiselo ye-KIE, ukwahlukana kwe-CH kunomqobo wamandla okusabela ophezulu kakhulu kunamanye amanyathelo okusabela kwaye kumela i-RDS. Umqobo wamandla wenkqubo ye-catalyst ye-Co-SAs/NPs@NC efanelekileyo yi-0.86 eV ephantsi kuneye-Co-SA (1.2 eV), nto leyo ephucula kakhulu ukusebenza kakuhle kwe-dehydrogenation. Okuphawulekayo kukuba, ubukho bee-nanoparticles bulawula ulwakhiwo lwe-elektroniki lweendawo ze-coactive ezisasazeke ngeathomu, nto leyo ephucula ngakumbi ukutsalwa kunye nokusebenza kwe-intermediates, ngaloo ndlela inciphisa umqobo wokusabela kwaye ikhuthaza imveliso ye-hydrogen.
Ngamafutshane, sibonisa okokuqala ukuba ukusebenza kwe-catalytic kwe-hydrogen production catalysts kunokuphuculwa kakhulu ngokusebenzisa izinto ezine-monometallic centers ezisasazwe kakhulu kunye ne-nanoparticles ezincinci. Le ngcamango iqinisekiswe ngokudityaniswa kwe-cobalt-based single-atom metal catalysts eziguqulwe nge-nanoparticles (Co-SAs/NPs@NC), kunye nezinto ezinxulumene nazo ezine-single-metal centers kuphela (CoN2C2) okanye i-Co NPs. Zonke izinto zilungiswe ngendlela elula ye-pyrolysis. Uhlalutyo lwesakhiwo lubonisa ukuba i-catalyst engcono kakhulu (Co-SAs/NPs@NC-950) iqulethe iiyunithi ze-CoN2C2 ezisasazwe ngeathomu kunye ne-nanoparticles ezincinci (7-8 nm) ezifakwe i-nitrogen kunye ne-graphite-like carbon. Inemveliso entle kakhulu yegesi ukuya kuthi ga kwi-1403.8 ml g-1 h-1 (H2:CO2 = 1.01:1), i-H2 kunye ne-CO selectivity ye-99.96% kwaye inokugcina umsebenzi oqhubekayo kangangeentsuku ezininzi. Umsebenzi wale catalyst udlula umsebenzi wee-catalysts ezithile ze-CoSA kunye ne-Pd/C ngamaxesha ama-4 nangama-15, ngokulandelelana. Uvavanyo lwe-DRIFT olukwindawo lubonisa ukuba xa kuthelekiswa ne-Co-SA, i-Co-SAs/NPs@NC-950 ibonisa ukutsalwa kwe-HCOO* okunamandla, okubalulekileyo kwindlela yokwenza i-formate, kwaye ii-nanoparticles ze-dopant zinokukhuthaza ukusebenza kwe-HCOO* kunye nokukhawuleziswa kwe-C-H. Ukuqhekeka kwebhondi kwachongwa njenge-RDS. Ubalo lwethiyori lubonisa ukuba ukutsalwa kwe-Co NP kwandisa iziko le-d-band yee-athomu ze-Co enye nge-0.13 eV ngokusebenzisana, kuphucula ukutsalwa kwe-HCOOH* kunye nee-intermediates ze-HCOO*, ngaloo ndlela kunciphisa umqobo wokusabela ukusuka kwi-1.20 eV ye-Co SA ukuya kwi-0 .86 eV. Unoxanduva lokusebenza okugqwesileyo.
Ngokubanzi, olu phando lubonelela ngeengcinga zoyilo lwee-catalysts ezintsha zesinyithi ze-atom enye kwaye luqhubela phambili ukuqonda indlela yokuphucula ukusebenza kwe-catalytic ngokusebenzisa isiphumo sokusebenzisana kwamaziko esinyithi anobukhulu obahlukeneyo. Sikholelwa ukuba le ndlela inokwandiswa ngokulula nakwezinye iinkqubo ezininzi ze-catalytic.
I-Co(NO3)2 6H2O (AR, 99%), i-Zn(NO3)2 6H2O (AR, 99%), i-2-methylimidazole (98%), i-methanol (99.5%), i-propylene carbonate (PC, 99%) ethanol (AR, 99.7%) ithengwe eMcLean, eTshayina. I-Formic acid (HCOOH, 98%) ithengwe eRhawn, eTshayina. Zonke ii-reagents zisetyenziswe ngokuthe ngqo ngaphandle kokucocwa okongeziweyo, kwaye amanzi acocekileyo kakhulu alungiswa kusetyenziswa inkqubo yokucoca ecocekileyo kakhulu. I-Pt/C (5% yokulayisha ubunzima) kunye ne-Pd/C (5% yokulayisha ubunzima) zithengwe eSigma-Aldrich.
Ukwenziwa kwee-nanocrystals zeCoZn-ZIF kwenziwe ngokusekelwe kwiindlela zangaphambili kunye notshintsho oluthile23,64. Okokuqala, i-30 mmol Zn(NO3)2·6H2O (8.925 g) kunye ne-3.5 mmol Co(NO3)2·6H2O (1.014 g) zaxutywa zaza zanyibilika kwi-300 ml ye-methanol. Emva koko, i-120 mmol ye-2-methylimidazole (9.853 g) yanyibilika kwi-100 ml ye-methanol yaza yongezwa kwisisombululo esingentla. Umxube wavuselelwa kubushushu begumbi iiyure ezingama-24. Ekugqibeleni, imveliso yahlulwe nge-centrifugation kwi-6429 g imizuzu eli-10 yaza yahlanjwa kakuhle nge-methanol kathathu. Umgubo ophumayo womiswa kwi-vacuum kwi-60°C ubusuku bonke ngaphambi kokusetyenziswa.
Ukuze kwenziwe i-Co-SAs/NPs@NC-950, umgubo owomileyo we-CoZn-ZIF watshiswa kwi-950 °C kangangeyure e-1 kumoya wegesi we-6% H2 + 94% Ar, ngesantya sokufudumeza se-5 °C/min. Emva koko isampuli yapholiswa kubushushu begumbi ukuze kufunyanwe i-Co-SA/NPs@NC-950. Kwi-Co-SAs/NPs@NC-850 okanye kwi-Co-SAs/NPs@NC-750, ubushushu be-pyrolysis batshintsha ukuya kwi-850 kunye ne-750 °C, ngokwahlukeneyo. Iisampulu ezilungisiweyo zingasetyenziswa ngaphandle kokuqhubekeka nokusebenza, njengokugrumba i-asidi.
Ukulinganiswa kwe-TEM (transmission electron microscopy) kwenziwe kwi-Thermo Fisher Titan Themis 60-300 "cube" microscope exhotyiswe nge-aberration corrector yokufota kunye ne-300 kV probe shaping lens. Uvavanyo lwe-HAADF-STEM lwenziwe kusetyenziswa ii-FEI Titan G2 kunye nee-FEI Titan Themis Z microscopes ezixhotyiswe ngee-probes kunye nee-image correctors, kunye nee-DF4 four-segment detectors. Imifanekiso ye-EDS elemental mapping ikwafunyenwe kwi-FEI Titan Themis Z microscope. Uhlalutyo lwe-XPS lwenziwe kwi-X-ray photoelectron spectrometer (Thermo Fisher model ESCALAB 250Xi). I-XANES kunye ne-EXAFS spectra ze-Co K-edge ziqokelelwe kusetyenziswa itafile ye-XAFS-500 (China Spectral Instruments Co., Ltd.). Umxholo we-Co umiselwe yi-atomic absorption spectroscopy (AAS) (PinAAcle900T). Iispectra ze-X-ray diffraction (XRD) zirekhodwe kwi-X-ray diffractometer (Bruker, Bruker D8 Advance, Germany). Ii-isotherms ze-nitrogen adsorption zifunyenwe kusetyenziswa isixhobo se-physical adsorption (Micromeritics, ASAP2020, USA).
I-reaction dehydrogenation yenziwe kwindawo ye-argon apho umoya ususiwe ngokwendlela eqhelekileyo yeSchlenk. I-reaction vessel yakhutshwa yaza yazaliswa nge-argon izihlandlo ezi-6. Vula unikezelo lwamanzi lwe-condenser uze wongeze i-catalyst (30 mg) kunye ne-solvent (6 ml). Fudumeza isitya kubushushu obufunekayo usebenzisa i-thermostat kwaye uyivumele ilingane imizuzu engama-30. I-Formic acid (10 mmol, 377 μL) yongezwa kwi-reaction vessel phantsi kwe-argon. Jika ivalvu ye-burette eneendlela ezintathu ukuze unciphise uxinzelelo kwi-reactor, uyivale kwakhona, kwaye uqale ukulinganisa umthamo wegesi eveliswayo usebenzisa i-burette yesandla (Umfanekiso S16). Emva kwexesha elifunekayo ukuze i-reaction igqitywe, isampuli yegesi yaqokelelwa ukuze kuhlalutywe i-GC kusetyenziswa isirinji engangenisi gesi ehlanjululwe nge-argon.
Uvavanyo lwe-Insitu drift lwenziwe kwi-Fourier transform infrared (FTIR) spectrometer (Thermo Fisher Scientific, Nicolet iS50) exhotyiswe nge-mercury cadmium telluride (MCT) detector. I-catalyst powder yafakwa kwi-reaction cell (Harrick Scientific Products, Praying Mantis). Emva kokunyanga i-catalyst ngomlambo we-Ar (50 ml/min) kubushushu begumbi, isampuli yafudunyezwa ukuya kubushushu obuthile, emva koko yafakwa amaqamza nge-Ar (50 ml/min) kwisisombululo se-HCOOH yaza yagalelwa kwi-in-situ reaction cell. ukuze iphendule. Iimodeli zeenkqubo ze-catalytic ezahlukeneyo. Ii-infrared spectra zarekhodwa ngamaxesha aphakathi ukusuka kwimizuzwana eyi-3.0 ukuya kwiyure e-1.
I-HCOOH, i-DCOOH, i-HCOOD kunye ne-DCOOD zisetyenziswa njengezinto ezisetyenziswa kwi-propylene carbonate. Ezinye iimeko zihambelana nenkqubo yokukhupha i-hydrogenation ye-HCOOH.
Imigaqo yokuqala yokubala yenziwe kusetyenziswa isakhelo sethiyori yokusebenza koxinano ngaphakathi kwiphakheji yemodeli yeVienna Ab initio (VASP 5.4.4) 65,66. Iseli ye-superunit enomphezulu we-graphene (5 × 5) enomlinganiselo onqamlezileyo omalunga ne-12.5 Å yasetyenziswa njengesiseko seCoN2C2 kunye neCoN2C2-Co6. Umgama we-vacuum ongaphezulu kwe-15 Å wongezwa ukuze kuthintelwe ukusebenzisana phakathi kweeleya zesiseko ezikufutshane. Ukusebenzisana phakathi kwee-ion kunye nee-electron kuchazwa yindlela ye-projected amplified wave (PAW) 65,67. Umsebenzi we-Perdue-Burke-Ernzerhoff (PBE) generalized gradient approximation (GGA) ocetyiswe yiGrimm kunye ne-van der Waals correction68,69 wasetyenziswa. Iikhrayitheriya zokuhlangana kwamandla apheleleyo kunye namandla yi-10−6 eV/atom kunye ne-0.01 eV/Å. Ukunqunyulwa kwamandla kumiselwe kwi-600 eV kusetyenziswa igridi yeMonkhorst-Pack 2 × 2 × 1 K-point. I-pseudopotential esetyenzisiweyo kule modeli yakhiwe ukusuka kwi-electronic configuration ukuya kwi-C 2s22p2 state, N 2s22p3 state, Co 3d74s2 state, H 1 s1 state, kunye ne-O 2s22p4 state. Amandla okutsalwa kwamandla kunye nomahluko wobuninzi be-electron kubalwa ngokuthabatha amandla esigaba segesi kunye neentlobo zomphezulu kumandla enkqubo etsalwa amandla ngokwemodeli ye-adsorption okanye ye-interface70,71,72,73,74. Ukulungiswa kwamandla asimahla eGibbs kusetyenziselwa ukuguqula amandla e-DFT abe ngamandla asimahla eGibbs kwaye kuthathelwa ingqalelo igalelo lokudlidliza kwi-entropy kunye namandla e-zero point75. Indlela ye-ascending image-nudging elastic band (CI-NEB) yasetyenziswa ukukhangela imeko yotshintsho lwe-reaction76.
Yonke idatha efunyenweyo nehlaziyiweyo ngeli xesha lophando ifakiwe kwinqaku kunye nezixhobo ezongezelelweyo okanye iyafumaneka kumbhali ohambelanayo xa iceliwe ngokufanelekileyo. Idatha yomthombo inikezelwe kweli nqaku.
Yonke ikhowudi esetyenzisiweyo kwiimodeli ezihamba neli nqaku iyafumaneka kubabhali abafanelekileyo xa iceliwe.
UDutta, I. et al. I-Formic acid ixhasa uqoqosho olunekhabhoni ephantsi. isihlomelo. Izixhobo zamandla. 12, 2103799 (2022).
Wei, D., Sang, R., Sponholz, P., Junge, H. kunye noBeller, M. I-hydrogenation eguqukayo ye-carbon dioxide ibe yi-formic acid xa kukho i-lysine kusetyenziswa ii-Mn-claw complexes. Nat. Energy 7, 438–447 (2022).
UWei, D. et al. Ukuya kuqoqosho lwe-hydrogen: uphuhliso lwee-catalysts ezahlukeneyo zokugcina i-hydrogen kunye ne-release chemistry. Iileta zamandla ze-ACS. 7, 3734–3752 (2022).
UModisha PM, uOuma SNM, uGarijirai R., uWasserscheid P. kunye noBessarabov D. Amathemba okugcinwa kwehydrogen kusetyenziswa ii-hydrogen carriers ezingamanzi eziphilayo. Amandla Amafutha 33, 2778–2796 (2019).
Niermann, M., Timmerberg, S., Drunert, S. kunye noKaltschmitt, M. Abathwali behydrogen yendalo engamanzi kunye nezinye iindlela zokuthutha ihydrogen evuselelekayo kwihlabathi liphela. uhlaziyo. inkxaso. amandla. Ivuliwe 135, 110171 (2021).
UPreister P, uPapp K kunye noWasserscheid P. Abathwali behydrogen yendalo engamanzi (LOHC): besiya kuqoqosho lwehydrogen olungenayo ihydrogen. ukusetyenziswa. Umthombo weekhemikhali. 50, 74–85 (2017).
UChen, Z. et al. Uphuhliso lwee-catalysts ze-palladium ezinokuthenjwa zokunciphisa i-asidi ye-formic. Ikhathalogu ye-AKS. 13, 4835–4841 (2023).
Sun, Q., Wang, N., Xu, Q. kunye noYu, J. Ii-nanocatalysts zesinyithi ezixhaswa yi-nanopore zokuvelisa i-hydrogen ngokufanelekileyo kwiikhemikhali zokugcina i-hydrogen zesigaba solwelo. isihlomelo. Matt. 32, 2001818 (2020).
Seraj, JJA, et al. Isincedisi esisebenzayo sokukhupha i-hydrogenation ye-asidi ye-formic ecocekileyo. I-Nat. communicate. 7, 11308 (2016).
UKar S., uRauch M., uLeithus G., uBen-David Y. kunye noMilstein D. Ukususwa kwe-hydrogenation ye-acid ecocekileyo ngaphandle kwezongezo. UNat. Gatar. 4, 193–201 (2021).
ULi, S. et al. Imigaqo elula nesebenzayo yoyilo olunengqiqo lwee-catalysts ze-formic acid dehydrogenation ezingafaniyo. isihlomelo. Matt. 31, 1806781 (2019).
ULiu, M. et al. I-catalysis eyahlukeneyo yeteknoloji yokugcina i-hydrogen kusetyenziswa i-formic acid-based carbon dioxide. isihlomelo. Izixhobo zamandla. 12, 2200817 (2022).