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ʻO ka hoʻomohala ʻana o nā ʻenehana hydrogen ke kumu o ka hoʻokele waiwai ʻōmaʻomaʻo. Ma ke ʻano he kūlana mua no ka hoʻokō ʻana i ka mālama ʻana i ka hydrogen, pono nā mea hoʻouluulu ikaika a paʻa no ka hopena hydrogenation (de)hydrogenation. A hiki i kēia manawa, ua hoʻomalu ʻia kēia wahi e ka hoʻohana ʻana i nā metala makamae pipiʻi. Maanei, ke hāpai nei mākou i kahi mea hoʻouluulu hou e pili ana i ka cobalt haʻahaʻa ke kumu kūʻai (Co-SAs/NPs@NC) kahi e hoʻopili pū ʻia ai nā wahi metala hoʻokahi i hoʻolaha nui ʻia me nā nanoparticles maikaʻi e hoʻokō ai i ka dehydrogenation waikawa formic. Ma ka hoʻohana ʻana i ka mea maikaʻi loa o nā ʻāpana CoN2C2 i hoʻopuehu ʻia i ka atomically a me nā nanoparticles i hoʻopuni ʻia o ka nui 7-8 nm, me ka hoʻohana ʻana i ka propylene carbonate ma ke ʻano he solvent, ua loaʻa kahi hana kinoea maikaʻi loa o 1403.8 ml g-1 h-1, a ʻaʻohe pohō ma hope o 5 mau pōʻaiapuni. hana, ʻo ia hoʻi he 15 mau manawa ʻoi aku ka maikaʻi ma mua o ka Pd/C kalepa. Hōʻike nā hoʻokolohua in situ assay, i ka hoʻohālikelike ʻia me nā mea hoʻouluulu atom metala hoʻokahi a me nā nanoparticle e pili ana, hoʻonui ʻo Co-SAs/NPs@NC i ka adsorption a me ka hoʻāla ʻana o ke kikowaena monodentate koʻikoʻi ʻo HCOO*, no laila e hoʻolaha ana i ka ʻoki ʻana o ka pilina CH ma hope. Hōʻike nā helu kumumanaʻo e hoʻolaha ka hoʻohui ʻana o nā nanoparticles cobalt i ka hoʻololi ʻana o ke kikowaena d-band o kahi atom Co hoʻokahi i kahi kahua hana, no laila e hoʻomaikaʻi ana i ka hoʻopili ʻana ma waena o ka carbonyl O o ka waena HCOO* a me ke kikowaena Co, no laila e hoʻohaʻahaʻa ana i ka pale ikehu.
Ua manaʻo ʻia ʻo Hydrogen he mea lawe ikehu koʻikoʻi no ka hoʻololi ikehu honua o kēia manawa a hiki ke lilo i mea hoʻokele koʻikoʻi no ka hoʻokō ʻana i ke kūpaʻa kalapona1. Ma muli o kona mau waiwai kino e like me ka lapalapa a me ka haʻahaʻa haʻahaʻa, ʻo ka mālama palekana a me ka lawe ʻana o ka hydrogen nā pilikia koʻikoʻi i ka hoʻokō ʻana i ka hoʻokele waiwai hydrogen2,3,4. Ua hāpai ʻia nā mea lawe hydrogen organik wai (LOHC), e mālama a hoʻokuʻu i ka hydrogen ma o nā hopena kemika, ma ke ʻano he hopena. Ke hoʻohālikelike ʻia me ka hydrogen molekala, ʻo ia mau mea (methanol, toluene, dibenzyltoluene, etc.) he maʻalahi a maʻalahi hoʻi e lawelawe5,6,7. Ma waena o nā LOHC kuʻuna like ʻole, he haʻahaʻa ka ʻawaʻawa formic (FA) (LD50: 1.8 g/kg) a me ka hiki ke H2 o 53 g/L a i ʻole 4.4 wt%. ʻO ka mea nui, ʻo FA wale nō ka LOHC hiki ke mālama a hoʻokuʻu i ka hydrogen ma lalo o nā kūlana akahai i ke alo o nā mea hoʻoulu kūpono, no laila ʻaʻole pono nā hoʻokomo ikehu waho nui1,8,9. ʻO kaʻoiaʻiʻo, ua hoʻomohala ʻia nā mea hoʻouluulu metala hanohano he nui no ka dehydrogenation o ka waikawa formic, no ka laʻana, ʻoi aku ka ikaika o nā mea hoʻouluulu palladium ma mua o 50-200 mau manawa ma mua o nā mea hoʻouluulu metala haʻahaʻa ke kumu kūʻai10,11,12. Eia nō naʻe, inā ʻoe e noʻonoʻo i ke kumukūʻai o nā metala hana, no ka laʻana, ʻoi aku ka pipiʻi o ka palladium ma mua o 1000 mau manawa.
ʻO Cobalt, Ke hoʻomau nei ka ʻimi ʻana i nā mea hoʻoulu metala kumu heterogeneous ikaika loa a paʻa hoʻi e huki i ka hoihoi o nā mea noiʻi he nui ma ke kula nui a me ka ʻoihana13,14,15.
ʻOiai ua hoʻomohala ʻia nā mea hoʻouluulu haʻahaʻa haʻahaʻa e pili ana iā Mo a me Co, a me nā nanocatalysts i hana ʻia mai nā metala koʻikoʻi/kumu,14,16 no ka dehydrogenation FA, ʻo kā lākou deactivation mālie i ka wā o ka hopena he mea hiki ʻole ke pale ʻia ma muli o ka noho ʻana o nā wahi hana o nā metala, CO2, a me H2O e nā protons. a i ʻole formate anions (HCOO-), FA contamination, particle aggregation a me ka hiki ke CO poisoning17,18. Ua hōʻike koke mākou a me nā poʻe ʻē aʻe i nā mea hoʻouluulu atom hoʻokahi (SACs) me nā wahi CoIINx i hoʻopuehu nui ʻia ma ke ʻano he mau wahi hana e hoʻomaikaʻi i ka reactivity a me ke kūpaʻa waikawa o ka formic acid dehydrogenation i hoʻohālikelike ʻia me nā nanoparticles17,19,20,21,22,23,24. I loko o kēia mau mea Co-NC, lawelawe nā ʻātoma N ma ke ʻano he mau wahi nui e hoʻolaha i ka deprotonation FA me ka hoʻomaikaʻi ʻana i ke kūpaʻa o ka hoʻonohonoho ʻana ma o ka hoʻonohonoho ʻana me ka ʻātoma Co waena, ʻoiai ʻo nā ʻātoma Co e hāʻawi i nā wahi adsorption H a hoʻolaha i ka CH22 scission, 25,26. ʻO ka mea pōʻino, ʻo ka hana a me ke kūpaʻa o kēia mau mea hoʻouluulu ua mamao loa ia mai nā mea hoʻouluulu metala hanohano homogeneous a heterogeneous o kēia wā (Kiʻi 1) 13.
Hiki ke hoʻopuka ʻia ka ikehu keu mai nā kumu hou e like me ka lā a i ʻole ka makani ma o ka electrolysis o ka wai. Hiki ke mālama ʻia ka hydrogen i hana ʻia me ka hoʻohana ʻana i ka LOHC, kahi wai nona ka hydrogenation a me ka dehydrogenation e hoʻohuli ʻia. I ke kaʻina dehydrogenation, ʻo ka huahana wale nō ka hydrogen, a hoʻihoʻi ʻia ka wai lawe i kona kūlana mua a hydrogenated hou. Hiki ke hoʻohana ʻia ka hydrogen i nā kikowaena kinoea, nā pila, nā hale ʻoihana, a me nā mea hou aku.
I kēia manawa, ua hōʻike ʻia e hiki ke hoʻonui ʻia ka hana kūloko o nā SAC kikoʻī i ke alo o nā ʻātoma metala like ʻole a i ʻole nā ​​​​wahi metala hou aʻe i hāʻawi ʻia e nā nanoparticles (NPs) a i ʻole nanoclusters (NCs)27,28. Wehe kēia i nā hiki no ka adsorption hou aʻe a me ka hoʻoulu ʻana o ka substrate, a me ka modulation o ke geometry a me ka hoʻonohonoho uila o nā wahi monatomic. Ma kēia ʻano, hiki ke hoʻonui ʻia ka adsorption/activation substrate, e hāʻawi ana i ka pono catalytic holoʻokoʻa maikaʻi29,30. Hāʻawi kēia iā mākou i ka manaʻo o ka hana ʻana i nā mea catalytic kūpono me nā wahi hana hybrid. ʻOiai ua hōʻike nā SAC i hoʻomaikaʻi ʻia i ka hiki ke nui i nā ʻano noi catalytic ākea31,32,33,34,35,36, i ka maikaʻi o kā mākou ʻike, ʻaʻole maopopo kā lākou kuleana i ka mālama ʻana i ka hydrogen. Ma kēia ʻano, hōʻike mākou i kahi hoʻolālā versatile a paʻa no ka synthesis o nā catalysts hybrid cobalt-based (Co-SAs/NPs@NCs) i haku ʻia me nā nanoparticles i wehewehe ʻia a me nā kikowaena metala pākahi. Hōʻike nā Co-SAs/NPs@NC i hoʻomaikaʻi ʻia i ka hana dehydrogenation waikawa formic maikaʻi loa, ʻoi aku ka maikaʻi ma mua o nā catalysts nanostructured non-noble (e like me CoNx, nā ʻātoma cobalt hoʻokahi, cobalt@NC a me γ-Mo2N) a me nā catalysts metala hanohano. Hōʻike ka ʻano in-situ a me nā helu DFT o nā catalysts hana e lawelawe nā wahi metala pākahi ma ke ʻano he mau wahi hana, a hoʻonui nā nanoparticles o kēia mea i hana ʻia i ke kikowaena d-band o nā ʻātoma Co, paipai i ka adsorption a me ka hoʻāla ʻana o HCOO*, no laila e hoʻohaʻahaʻa ana i ka pale ikehu o ka hopena. .
ʻO nā ʻōnaehana Zeolite imidazolate (ZIFs) he mau mea hoʻomākaukau ʻekolu-dimensional i wehewehe pono ʻia e hāʻawi ana i nā mea hoʻouluulu no nā mea kalapona i hoʻopili ʻia me ka nitrogen (nā mea hoʻouluulu metala-NC) e kākoʻo i nā ʻano metala like ʻole37,38. No laila, hui pū ʻo Co(NO3)2 a me Zn(NO3)2 me 2-methylimidazole i loko o ka methanol e hana i nā hui metala like i loko o ka hopena. Ma hope o ka centrifugation a me ka maloʻo ʻana, ua pyrolyzed ʻia ʻo CoZn-ZIF ma nā mahana like ʻole (750–950 °C) i loko o kahi lewa o 6% H2 a me 94% Ar. E like me ka mea i hōʻike ʻia ma ke kiʻi ma lalo nei, he ʻano ʻokoʻa nā ʻano hana o nā mea i loaʻa a ua kapa ʻia ʻo Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750 (Kiʻi 2a). ). Ua kikoʻī ʻia nā nānā hoʻokolohua kikoʻī o kekahi mau ʻanuʻu koʻikoʻi i ke kaʻina hana synthesis ma nā Kiʻi 1 a me 2. C1-C3. Ua hana ʻia ka diffraction X-ray mahana loli (VTXRD) e nānā i ka ulu ʻana o ka mea hoʻoulu. Ke hiki ka mahana pyrolysis i 650 °C, loli nui ke ʻano XRD ma muli o ka hiolo ʻana o ke ʻano kristal i kauoha ʻia o ZIF (Kiʻi S4) 39. I ka piʻi ʻana o ka mahana, ʻike ʻia ʻelua mau piko ākea ma nā ʻano XRD o Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750 ma 20-30° a me 40-50°, e hōʻike ana i ka piko o ke kalapona amorphous (Kiʻi C5). 40. He mea kūpono ke hoʻomaopopo ʻana he ʻekolu wale nō piko hiʻohiʻona i ʻike ʻia ma 44.2°, 51.5° a me 75.8°, no ka cobalt metala (JCPDS #15-0806), a me 26.2°, no ke kalapona graphitic (JCPDS # 41-1487). Hōʻike ka spectrum X-ray o Co-SAs/NPs@NC-950 i ke alo o nā nanoparticles cobalt encapsulated like graphite ma ka catalyst41,42,43,44. Hōʻike ka spectrum Raman he ʻoi aku ka ikaika a me ka haiki o nā piko D a me G o Co-SAs/NPs@NC-950 ma mua o nā laʻana ʻē aʻe, e hōʻike ana i kahi kiʻekiʻe o ka graphitization (Kiʻi S6). Eia kekahi, hōʻike ʻo Co-SAs/NPs@NC-950 i ka ʻili o Brunner-Emmett-Taylor (BET) a me ka nui o ka pore (1261 m2 g-1 a me 0.37 cm3 g-1) ma mua o nā laʻana ʻē aʻe a ʻo ka hapa nui o nā ZIF he mau mea NC derivatives. Hōʻike ka spectroscopy absorption atomic (AAS) ʻo ka nui o ka cobalt o Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 a me Co-SAs/NPs@ he 2.69 wt.%, 2.74 wt.% a me 2.73 wt.%. NC-750 pakahi (Papa S2). Piʻi mālie ka nui o Zn o Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750, kahi i pili i ka hoʻonui ʻia ʻana o ka hōʻemi a me ka volatilization o nā ʻāpana Zn. Hoʻonui ʻia ka mahana pyrolysis (Zn, kiko paila = 907 °C) 45.46. Ua hōʻike ka loiloi elemental (EA) e emi ana ka pakeneka o N me ka hoʻonui ʻana i ka mahana pyrolysis, a ʻo ke kiʻekiʻe o ka nui o O ma muli paha o ka adsorption o ka molecular O2 mai ka ʻike ʻana i ka lewa. (Papa S3). Ma kahi o ka nui o ka cobalt, hui pū nā nanoparticles a me nā coatoms i hoʻokaʻawale ʻia, e hopena ana i ka hoʻonui nui ʻana o ka hana catalyst, e like me ka mea i kūkākūkā ʻia ma lalo nei.
Kiʻikuhi kiʻikuhi o ka synthesis o Co-SA/NPs@NC-T, kahi ʻo T ka mahana pyrolysis (°C). b kiʻi TEM. c Kiʻi o Co-SAs/NPs@NC-950 AC-HAADF-STEM. Ua hōʻailona ʻia nā ʻātoma Co hoʻokahi me nā pōʻai ʻulaʻula. d EDS spectrum o Co-SA/NPs@NC-950.
ʻIke ʻia, ua hōʻike ka microscopy electron transmission (TEM) i ke alo o nā nanoparticles cobalt like ʻole (NPs) me ka nui awelika o 7.5 ± 1.7 nm wale nō ma Co-SAs/NPs@NC-950 (Nā Kiʻi 2 b a me S8). Hoʻopili ʻia kēia mau nanoparticles me ke kalapona graphite-like i hoʻohui ʻia me ka nitrogen. ʻO ka lattice fringe spacing o 0.361 a me 0.201 nm e pili ana i nā ʻāpana kalapona graphitic (002) a me nā ʻāpana Co (111) metallic. Eia kekahi, ua hōʻike ka microscopy electron transmission annular dark-field scanning high-angle aberration-corrected (AC-HAADF-STEM) ua hoʻopuni ʻia nā Co NPs ma Co-SAs/NPs@NC-950 e ka cobalt atomic nui (Kiʻi 2c). Eia naʻe, ua ʻike wale ʻia nā ʻātoma cobalt i hoʻopuehu ʻia ma ke kākoʻo o nā laʻana ʻelua ʻē aʻe (Kiʻi S9). Hōʻike ke kiʻi HAADF-STEM o ka spectroscopy hoʻolaha ikehu (EDS) i ka hoʻolaha like ʻana o C, N, Co a me nā Co NP i hoʻokaʻawale ʻia ma Co-SAs/NPs@NC-950 (Kiʻi 2d). Hōʻike kēia mau hopena a pau ua hoʻopili pono ʻia nā kikowaena Co i hoʻolaha ʻia me nā atomically a me nā nanoparticles i hoʻopili ʻia i loko o ke kalapona graphite-like N-doped i nā substrates NC ma Co-SAs/NPs@NC-950, ʻoiai nā kikowaena metala i hoʻokaʻawale wale ʻia.
Ua aʻo ʻia ke kūlana valence a me ka hoʻohuihui kemika o nā mea i loaʻa e ka X-ray photoelectron spectroscopy (XPS). Ua hōʻike nā spectra XPS o nā catalysts ʻekolu i ke alo o nā mea Co, N, C a me O, akā aia wale nō ʻo Zn ma Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750 (Kiʻi 2). ). C10). I ka piʻi ʻana o ka mahana pyrolysis, emi ka nui o ka nitrogen i ka wā e lilo ai nā ʻano nitrogen i mea paʻa ʻole a palaho i loko o nā kinoea NH3 a me NOx ma nā mahana kiʻekiʻe (Papa S4) 47. No laila, ua piʻi mālie ka nui o ke kalapona mai Co-SAs/NPs@NC-750 a i Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-950 (Nā Kiʻi S11 a me S12). ʻO ka laʻana i pyrolyzed ma ka mahana kiʻekiʻe he haʻahaʻa ka hapa o nā ʻātoma nitrogen, ʻo ia hoʻi, ʻo ka nui o nā mea lawe NC ma Co-SAs/NPs@NC-950 e emi iho ma mua o nā laʻana ʻē aʻe. ʻO kēia ke alakaʻi ʻana i ka sintering ikaika o nā ʻāpana cobalt. Hōʻike ka spectrum O 1s i ʻelua mau piko C=O (531.6 eV) a me C–O (533.5 eV), kēlā me kēia (Kiʻi S13) 48. E like me ka mea i hōʻike ʻia ma ke Kiʻi 2a, hiki ke hoʻoholo ʻia ka spectrum N 1s i ʻehā mau piko hiʻohiʻona o ka pyridine nitrogen N (398.4 eV), pyrrole N (401.1 eV), graphite N (402.3 eV) a me Co-N (399.2 eV). Loaʻa nā pilina Co-N i nā laʻana ʻekolu, e hōʻike ana ua hoʻonohonoho ʻia kekahi mau ʻātoma N i nā wahi monometallic, akā ʻokoʻa loa nā ʻano49. ʻO ka hoʻopili ʻana o ka mahana pyrolysis kiʻekiʻe hiki ke hōʻemi nui i ka ʻike o nā ʻano Co-N mai 43.7% ma Co-SA/NPs@NC-750 a i 27.0% ma Co-SAs/NPs@NC-850 a me Co 17.6%@ NC-950. i loko o -CA/NPs, kahi e pili ana i ka hoʻonui ʻia ʻana o ka ʻike C (Kiʻi 3a), e hōʻike ana e hiki ke loli kā lākou helu hoʻohui Co-N a pani hapa ʻia e nā ʻātoma C50. Hōʻike ka spectrum Zn 2p e noho nui ana kēia mea ma ke ʻano Zn2+. (Kiʻi S14) 51. Hōʻike ka spectrum o Co 2p i ʻelua mau piko koʻikoʻi ma 780.8 a me 796.1 eV, i hāʻawi ʻia iā Co 2p3/2 a me Co 2p1/2, kēlā me kēia (Kiʻi 3b). Ke hoʻohālikelike ʻia me Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750, ua hoʻoneʻe ʻia ka piko Co-N ma Co-SAs/NPs@NC-950 i ka ʻaoʻao maikaʻi, e hōʻike ana he kiʻekiʻe aʻe ka emi ʻana o ka electron i ka ʻātoma Co hoʻokahi i ka ʻili -SAs/NPs@NC-950, e hopena ana i kahi kūlana oxidation kiʻekiʻe. He mea kūpono ke hoʻomaopopo ʻana ʻo Co-SAs/NPs@NC-950 wale nō i hōʻike i kahi piko nāwaliwali o ka cobalt zero-valent (Co0) ma 778.5 eV, ka mea e hōʻoiaʻiʻo ana i ke ola ʻana o nā nanoparticles i loaʻa mai ka hōʻuluʻulu ʻana o ka cobalt SA ma nā mahana kiʻekiʻe.
a N 1s a me b Co 2p spectra o Co-SA/NPs@NC-T. c XANES a me d FT-EXAFS spectra o Co-K-edge o Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750. e Nā kiʻi contour WT-EXAFS o Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850, a me Co-SAs/NPs@NC-750. f Piʻo kūpono FT-EXAFS no Co-SA/NPs@NC-950.
A laila ua hoʻohana ʻia ka spectroscopy absorption X-ray i hoʻopaʻa ʻia i ka manawa (XAS) e kālailai i ke ʻano uila a me ke kaiapuni hoʻonohonoho o nā ʻano Co i loko o ka hāpana i hoʻomākaukau ʻia. ʻO nā kūlana valence Cobalt ma Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750 Edge structure i hōʻike ʻia e ka normalized near-field X-ray absorption ma ka Co-K edge (XANES) spectrum. E like me ka mea i hōʻike ʻia ma ke Kiʻi 3c, aia ka absorption kokoke i ka lihi o nā hāpana ʻekolu ma waena o nā foils Co a me CoO, e hōʻike ana ʻo ke kūlana valence o nā ʻano Co mai 0 a +253. Eia kekahi, ua ʻike ʻia kahi hoʻololi i ka ikehu haʻahaʻa mai Co-SAs/NPs@NC-950 a i Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750, e hōʻike ana he haʻahaʻa ka mokuʻāina oxidation o Co-SAs/NPs@NC-750. Hoʻohuli ʻia ke kauoha. Wahi a nā hopena hoʻopili hui linear, ua manaʻo ʻia ke kūlana valence Co o Co-SAs/NPs@NC-950 he +0.642, ʻoi aku ka haʻahaʻa ma mua o ke kūlana valence Co o Co-SAs/NPs@NC-850 (+1.376). Co-SA/NP @NC-750 (+1.402). Hōʻike kēia mau hopena ua emi nui ka awelika o ka mokuʻāina oxidation o nā ʻāpana cobalt ma Co-SAs/NPs@NC-950, kahi e kūlike me nā hopena XRD a me HADF-STEM a hiki ke wehewehe ʻia e ka noho pū ʻana o nā nanoparticles cobalt a me ka cobalt hoʻokahi. . ʻĀtoma Co 41. Hōʻike ka spectrum Fourier transform X-ray absorption fine structure (FT-EXAFS) o ka Co K-edge e pili ana ka piko nui ma 1.32 Å i ka pūpū Co-N/Co-C, ʻoiai ʻo ke ala hoʻopuehu o ka metala Co-Co ma 2.18 wale nō ma Co-SAs Å i loaʻa ma /NPs@NC-950 (Kiʻi 3d). Eia kekahi, hōʻike ka contour plot wavelet transform (WT) i ka ikaika nui loa ma 6.7 Å-1 i hoʻopili ʻia i Co-N/Co-C, ʻoiai ʻo Co-SAs/NPs@NC-950 wale nō e hōʻike ana i ka ikaika nui loa i hoʻopili ʻia i 8.8. ʻO kekahi ikaika nui loa ma Å−1 i ka pilina Co–Co (Kiʻi 3e). Eia kekahi, ua hōʻike ka loiloi EXAFS i hana ʻia e ka mea hoʻolimalima ma nā mahana pyrolysis o 750, 850 a me 950 °C, ʻo nā helu hoʻohui Co-N he 3.8, 3.2 a me 2.3, kēlā me kēia, a ʻo nā helu hoʻohui Co-C he 0. 0.9 a me 1.8 (Kiʻi 3f, S15 a me ka Papa S1). ʻOi aku ka kikoʻī, hiki ke hoʻopili ʻia nā hopena hou loa i ke alo o nā ʻāpana CoN2C2 i hoʻopuehu ʻia me ka atomically a me nā nanoparticles i loko o Co-SAs/NPs@NC-950. I ka hoʻohālikelike ʻana, i loko o Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750, aia wale nō nā ʻāpana CoN3C a me CoN4. He mea maopopo ia me ka hoʻonui ʻana o ka mahana pyrolysis, ua pani mālie ʻia nā ʻātoma N i loko o ka ʻāpana CoN4 e nā ʻātoma C, a hui pū nā cobalt CA e hana i nā nanoparticles.
Ua hoʻohana ʻia nā kūlana hana i aʻo mua ʻia e aʻo i ka hopena o nā kūlana hoʻomākaukau ma nā waiwai o nā mea like ʻole (Kiʻi S16)17,49. E like me ka mea i hōʻike ʻia ma ke Kiʻi 4 a, ʻoi aku ka kiʻekiʻe o ka hana o Co-SAs/NPs@NC-950 ma mua o Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750. ʻIke ʻia, ua hōʻike nā laʻana Co i hoʻomākaukau ʻia ʻekolu i ka hana maikaʻi loa i hoʻohālikelike ʻia me nā mea hoʻoulu metala makamae kalepa maʻamau (Pd/C a me Pt/C). Eia kekahi, ʻaʻole hana nā laʻana Zn-ZIF-8 a me Zn-NC i ka dehydrogenation waikawa formic, e hōʻike ana ʻaʻole nā ​​​​​​ʻāpana Zn he mau wahi hana, akā he mea liʻiliʻi ko lākou hopena ma ka hana. Eia kekahi, ua hana ʻia ka hana o Co-SAs/NPs@NC-850 a me Co-SAs/NPs@NC-750 i ka pyrolysis lua ma 950°C no 1 hola, akā ua haʻahaʻa ma mua o Co-SAs/NPs@NC-750. @NC-950 (Kiʻi S17). Ua hōʻike ke ʻano kūkulu o kēia mau mea i ke alo o nā nanoparticles Co i loko o nā laʻana i hoʻoulu hou ʻia, akā ʻo ka ʻili kikoʻī haʻahaʻa a me ka nele o ke kalapona e like me ka graphite i hopena i ka hana haʻahaʻa i hoʻohālikelike ʻia me Co-SAs/NPs@NC-950 (Kiʻi S18–S20). Ua hoʻohālikelike ʻia hoʻi ka hana o nā laʻana me nā nui like ʻole o ka precursor Co, me ka hana kiʻekiʻe loa i hōʻike ʻia ma ka hoʻohui ʻana o 3.5 mol (Papa S6 a me Kiʻi S21). He mea maopopo ia ua hoʻopili ʻia ka hoʻokumu ʻia ʻana o nā kikowaena metala like ʻole e ka ʻike hydrogen i ka lewa pyrolysis a me ka manawa pyrolysis. No laila, ua loiloi ʻia nā mea Co-SAs/NPs@NC-950 ʻē aʻe no ka hana dehydrogenation waikawa formic. Ua hōʻike nā mea āpau i ka hana waena a maikaʻi loa; akā naʻe, ʻaʻohe o lākou i ʻoi aku ka maikaʻi ma mua o Co-SAs/NPs@NC-950 (Nā Kiʻi S22 a me S23). Ua hōʻike ʻia ke ʻano hoʻonohonoho o ka mea me ka hoʻonui ʻana i ka manawa pyrolysis, e emi mālie ana ka nui o nā kūlana Co-N monoatomic ma muli o ka hōʻuluʻulu ʻana o nā ʻātoma metala i loko o nā nanoparticles, e wehewehe ana i ka ʻokoʻa o ka hana ma waena o nā laʻana me ka manawa pyrolysis o 100-2000. ʻokoʻa. 0.5 h, 1 h, a me 2 h (Nā Kiʻi S24–S28 a me ka Papa S7).
ʻO ke kiʻikuhi o ka nui o ke kinoea e kūʻē i ka manawa i loaʻa i ka wā o ka dehydrogenation o nā ʻākoakoa wahie me ka hoʻohana ʻana i nā mea hoʻouluulu like ʻole. Nā kūlana hana: PC (10 mmol, 377 μl), mea hoʻouluulu (30 mg), PC (6 ml), Tback: 110 °C, Tactical: 98 °C, 4 ʻāpana b Co-SAs/NPs@NC-950 (30 mg), nā mea hoʻoheheʻe like ʻole. c Hoʻohālikelike i nā helu hoʻomohala kinoea o nā mea hoʻouluulu heterogeneous i nā mea hoʻoheheʻe organik ma 85-110 °C. d Hoʻokolohua hana hou ʻana o Co-SA/NPs@NC-950. Nā kūlana hana: FA (10 mmol, 377 µl), Co-SAs/NPs@NC-950 (30 mg), mea hoʻoheheʻe (6 ml), Tset: 110 °C, Tactual: 98 °C, hoʻokahi hola ka lōʻihi o kēlā me kēia pōʻaiapuni hana. Hōʻike nā kaha hewa i nā ʻokoʻa maʻamau i helu ʻia mai ʻekolu mau hoʻāʻo hana.
Ma keʻano laulā, ʻo ka pono o nā mea hoʻouluulu dehydrogenation FA e hilinaʻi nui ʻia i nā kūlana hopena, ʻoiai ka mea hoʻoheheʻe i hoʻohana ʻia8,49. I ka wā e hoʻohana ai i ka wai ma ke ʻano he mea hoʻoheheʻe, ua hōʻike ʻo Co-SAs/NPs@NC-950 i ka nui o ka hopena mua loa, akā ua hana ʻia ka deactivation, ma muli paha o nā protons a i ʻole H2O18 e noho ana i nā wahi hana. ʻO ka hoʻāʻo ʻana o ka mea hoʻouluulu i nā mea hoʻoheheʻe organik e like me 1,4-dioxane (DXA), n-butyl acetate (BAC), toluene (PhMe), triglyme a me cyclohexanone (CYC) ʻaʻole hoʻi i hōʻike i kekahi hoʻomaikaʻi ʻana, a ma ka propylene carbonate (PC)) (Kiʻi 4b a me ka Papa S8). Pēlā nō, ʻaʻohe hopena maikaʻi hou aʻe o nā mea hoʻohui e like me triethylamine (NEt3) a i ʻole sodium formate (HCCONa) i ka hana catalyst (Kiʻi S29). Ma lalo o nā kūlana hopena kūpono loa, ua hōʻea ka hua kinoea i 1403.8 mL g−1 h−1 (Kiʻi S30), ʻoi aku ka kiʻekiʻe ma mua o nā mea hoʻoulu Co i hōʻike mua ʻia (me SAC17, 23, 24). Ma nā hoʻokolohua like ʻole, me ka hoʻokoe ʻana i nā hopena i ka wai a me nā mea hoʻohui formate, ua loaʻa nā koho dehydrogenation a me dehydration a hiki i ka 99.96% (Papa S9). ʻO ka ikehu hoʻāla i helu ʻia he 88.4 kJ/mol, kahi e like me ka ikehu hoʻāla o nā mea hoʻoulu metala hanohano (Kiʻi S31 a me ka Papa S10).
Eia kekahi, ua hoʻohālikelike mākou i kekahi mau mea hoʻouluulu heterogeneous ʻē aʻe no ka dehydrogenation waikawa formic ma lalo o nā kūlana like (Kiʻi 4c, nā papa S11 a me S12). E like me ka mea i hōʻike ʻia ma ke Kiʻi 3c, ʻoi aku ka nui o ka hana kinoea o Co-SAs/NPs@NC-950 ma mua o nā mea hoʻouluulu metala kumu heterogeneous i ʻike nui ʻia a he 15 a me 15 mau manawa kiʻekiʻe ma mua o ka 5% Pd/C kalepa a me 5% Pd/C, kēlā me kēia, ma 10 hoʻokahi manawa. % Pt/C mea hoʻouluulu.
ʻO kahi hiʻohiʻona koʻikoʻi o kekahi hoʻohana pono ʻana o nā mea hoʻouluulu (de)hydrogenation ko lākou kūpaʻa. No laila, ua hoʻokō ʻia kahi moʻo o nā hoʻokolohua hana hou e hoʻohana ana iā Co-SAs/NPs@NC-950. E like me ka mea i hōʻike ʻia ma ke Kiʻi 4 d, ua noho mau ka hana mua a me ke koho ʻana o ka mea ma luna o ʻelima mau holo hoʻomau (e nānā pū i ka Papa S13). Ua hana ʻia nā hoʻokolohua lōʻihi a ua hoʻonui linear ʻia ka hana kinoea ma luna o 72 mau hola (Kiʻi S32). ʻO ka nui o ka cobalt o ka Co-SA/NPs@NC-950 i hoʻohana ʻia he 2.5 wt%, kahi kokoke loa i ka mea hoʻouluulu hou, e hōʻike ana ʻaʻohe leaching maopopo o ka cobalt (Papa S14). ʻAʻohe loli kala maopopo a i ʻole ka hōʻuluʻulu ʻana o nā ʻāpana metala i ʻike ʻia ma mua a ma hope o ka hopena (Kiʻi S33). Ua hōʻike ʻo AC-HAADF-STEM a me EDS o nā mea i hoʻopili ʻia i nā hoʻokolohua lōʻihi i ka paʻa ʻana a me ka hoʻopuehu like ʻana o nā wahi hoʻopuehu atomika a ʻaʻohe loli koʻikoʻi o ke ʻano (Nā Kiʻi S34 a me S35). Aia nō nā piko hiʻona o Co0 a me Co-N ma XPS, e hōʻoia ana i ka noho pū ʻana o Co NPs a me nā wahi metala pākahi, kahi e hōʻoiaʻiʻo ai i ke kūpaʻa o ka mea hoʻoulu Co-SAs/NPs@NC-950 (Kiʻi S36).
No ka ʻike ʻana i nā wahi hana nui loa i kuleana no ka dehydrogenation waikawa formic, ua hoʻomākaukau ʻia nā mea i koho ʻia me hoʻokahi wale nō kikowaena metala (CoN2C2) a i ʻole Co NP ma muli o nā haʻawina mua17. ʻO ke kaʻina o ka hana dehydrogenation waikawa formic i ʻike ʻia ma lalo o nā kūlana like ʻo Co-SAs/NPs@NC-950 > Co SA > Co NP (Papa S15), e hōʻike ana he ʻoi aku ka hana o nā wahi CoN2C2 i hoʻopuehu ʻia ma ke ʻano atomically ma mua o NPs. Hōʻike ka kinetics o ka hopena e hahai ana ka evolution hydrogen i nā kinetics hopena mua, akā ʻaʻole like nā pali o kekahi mau piʻo ma nā ʻano cobalt like ʻole, e hōʻike ana ʻaʻole hilinaʻi wale ka kinetics i ka waikawa formic, akā ma ke kahua hana (Kiʻi 2). C37). Ua hōʻike ʻia nā haʻawina kinetic hou aʻe, no ka loaʻa ʻole o nā piko metala cobalt i ka nānā ʻana o ka diffraction X-ray, ua ʻike ʻia ke kaʻina kinetic o ka hopena ma ke ʻano o ka ʻike cobalt he 1.02 ma nā pae haʻahaʻa (emi ma mua o 2.5%), e hōʻike ana i kahi hoʻolaha like o nā kikowaena cobalt monoatomic. nui. kahua hana (kiʻi S38 a me S39). Ke hiki aku ka nui o nā ʻāpana Co i 2.7%, piʻi koke ʻo r, e hōʻike ana e launa maikaʻi ana nā nanoparticles me nā ʻātoma pākahi e loaʻa ai ka hana kiʻekiʻe. I ka piʻi ʻana o ka nui o nā ʻāpana Co, lilo ke kūlou i nonlinear, kahi e pili ana me ka hoʻonui ʻana i ka helu o nā nanoparticles a me ka emi ʻana o nā kūlana monatomic. No laila, ʻo ka hana dehydrogenation LC i hoʻomaikaʻi ʻia o Co-SA/NPs@NC-950 ka hopena mai ka hana hui pū ʻana o nā wahi metala pākahi a me nā nanoparticles.
Ua hana ʻia kahi noiʻi hohonu me ka hoʻohana ʻana i ka in situ diffuse reflectance Fourier transform (in situ DRIFT) e ʻike i nā mea waena o ka hopena i ke kaʻina hana. Ma hope o ka hoʻomehana ʻana i nā laʻana i nā mahana hopena like ʻole ma hope o ka hoʻohui ʻana i ka waikawa formic, ua ʻike ʻia ʻelua mau alapine (Kiʻi 5a). ʻEkolu mau piko hiʻohiʻona o HCOOH* e ʻike ʻia ma 1089, 1217 a me 1790 cm-1, i hāʻawi ʻia i ka haʻalulu hoʻolōʻihi CH π (CH) ma waho o ka mokulele, ka haʻalulu hoʻolōʻihi CO ν (CO) a me ka haʻalulu hoʻolōʻihi C=O ν (C=O), 54, 55 pakahi. ʻO kekahi hui o nā piko ma 1363 a me 1592 cm-1 e pili ana i ka haʻalulu OCO symmetric νs(OCO) a me ka haʻalulu hoʻolōʻihi OCO asymmetric νas(OCO)33.56 HCOO*, pakahi. I ka holomua ʻana o ka hopena, e mae mālie ana nā piko pili o nā ʻano HCOOH* a me HCOO*. Ma ke ʻano laulā, ʻo ka hoʻokaʻawale ʻana o ka waikawa formic e pili ana i ʻekolu mau ʻanuʻu nui: (I) ka adsorption o ka waikawa formic ma nā wahi hana, (II) ka wehe ʻana o H ma o ke ala formate a i ʻole carboxylate, a me (III) ka hui pū ʻana o ʻelua H i hoʻokaʻawale ʻia e hana i ka hydrogen. ʻO HCOO* a me COOH* nā mea waena koʻikoʻi i ka hoʻoholo ʻana i nā ala formate a i ʻole carboxylate, kēlā me kēia57. Ma ka hoʻohana ʻana i kā mākou ʻōnaehana catalytic, ʻo ka piko HCOO* hiʻohiʻona wale nō i ʻike ʻia, e hōʻike ana e hana wale ʻia ka hoʻokaʻawale ʻana o ka waikawa formic ma o ke ala waikawa formic58. Ua hana ʻia nā nānā like ma nā mahana haʻahaʻa o 78 °C a me 88 °C (kiʻi S40).
ʻO nā spectra DRIFT ma kahi o ka dehydrogenation HCOOH ma kahi Co-SAs/NPs@NC-950 a me b Co SAs. Hōʻike ka moʻolelo i nā manawa hana ma kahi. c ʻO ka loli o ka nui o ke kinoea i hana ʻia me ka hoʻohana ʻana i nā reagents lepili isotope like ʻole i ka hala ʻana o ka manawa. d ʻIkepili hopena isotope kinetic.
Ua hoʻokō ʻia nā hoʻokolohua DRIFT like ma nā mea pili ʻo Co NP a me Co SA e aʻo i ka hopena synergistic ma Co-SA/NPs@NC-950 (Nā Kiʻi 5 b a me S41). Hōʻike nā mea ʻelua i nā ʻano like, akā ua neʻe iki nā piko hiʻona o HCOOH* a me HCOO*, e hōʻike ana i ka hoʻokomo ʻana o Co NPs e hoʻololi i ke ʻano uila o ke kikowaena monoatomic. ʻIke ʻia kahi piko hiʻona νas(OCO) ma Co-SAs/NPs@NC-950 a me Co SA akā ʻaʻole ma Co NPs, e hōʻike hou ana i ka waena i hana ʻia ma ka hoʻohui ʻana o ka waikawa formic he monodentate formic acid perpendicular i ka ʻili paʻakai mokulele. a ua adsorbed ma luna o SA ma ke ʻano he wahi hana 59. He mea kūpono ke hoʻomaopopo ʻana ua ʻike ʻia kahi piʻi nui o nā haʻalulu o nā piko hiʻona π(CH) a me ν(C = O), kahi i alakaʻi ai i ka hoʻololi ʻana o HCOOH* a hoʻomaʻamaʻa i ka hopena. ʻO ka hopena, ua aneane nalowale nā ​​​​piko hiʻohiʻona o HCOOH* a me HCOO* ma Co-SAs/NPs@NC ma hope o 2 min o ka hopena, ʻoi aku ka wikiwiki ma mua o ka monometallic (6 min) a me nā mea hoʻouluulu nanoparticle (12 min). . Hōʻoia kēia mau hopena a pau e hoʻonui ka doping nanoparticle i ka adsorption a me ka hoʻāla ʻana o nā mea waena, no laila e hoʻolalelale ana i nā hopena i manaʻo ʻia ma luna.
No ka hoʻopili hou ʻana i ke ala o ka hopena a me ka hoʻoholo ʻana i ke kaʻina hana hoʻoholo wikiwiki (RDS), ua hoʻokō ʻia ka hopena KIE i ke alo o Co-SAs/NPs@NC-950. Maanei, hoʻohana ʻia nā isotopes waikawa formic like ʻole e like me HCOOH, HCOOD, DCOOH a me DCOOD no nā haʻawina KIE. E like me ka mea i hōʻike ʻia ma ke Kiʻi 5c, ua emi ka wikiwiki o ka dehydrogenation ma ke ʻano penei: HCOOH > HCOOD > DCOOH > DCOOD. Eia kekahi, ua helu ʻia nā waiwai o KHCOOH/KHCOOD, KHCOOH/KDCOOH, KHCOOD/KDCOOD a me KDCOOH/KDCOOD he 1.14, 1.71, 2.16 a me 1.44, kēlā me kēia (Kiʻi 5d). No laila, ʻo ka ʻoki ʻana o ka pilina CH ma HCOO* e hōʻike ana i nā waiwai kH/kD >1.5, e hōʻike ana i kahi hopena kinetic nui60,61, a ʻike ʻia e hōʻike ana i ka RDS o ka dehydrogenation HCOOH ma Co-SAs/NPs@NC-950.
Eia kekahi, ua hana ʻia nā helu DFT e hoʻomaopopo i ka hopena o nā nanoparticles i hoʻohui ʻia ma ka hana kūloko o Co-SA. Ua kūkulu ʻia nā hiʻohiʻona Co-SAs/NPs@NC a me Co-SA ma muli o nā hoʻokolohua i hōʻike ʻia a me nā hana ma mua (Figs. 6a a me S42)52,62. Ma hope o ka hoʻonui ʻana o ke ʻano geometric, ua ʻike ʻia nā nanoparticles Co6 liʻiliʻi (CoN2C2) e noho pū ana me nā ʻāpana monoatomic, a ua hoʻoholo ʻia nā lōʻihi o ka pilina Co-C a me Co-N ma Co-SA/NPs@NC he 1.87 Å a me 1.90 Å, kēlā me kēia. , kahi e kūlike me nā hopena XAFS. Hōʻike ka helu ʻana o ka density partial o nā mokuʻāina (PDOS) e hōʻike ana ka atom Co metal hoʻokahi a me ka nanoparticle composite (Co-SAs/NPs@NC) i ka hybridization kiʻekiʻe kokoke i ka pae Fermi i hoʻohālikelike ʻia me CoN2C2, e hopena ana i ka HCOOH. ʻOi aku ka maikaʻi o ka hoʻoili ʻana o ka electron decomposed (Nā Kiʻi 6b a me S43). Ua helu ʻia nā kikowaena d-band pili o Co-SAs/NPs@NC a me Co-SA he -0.67 eV a me -0.80 eV, kēlā me kēia, ʻo ia hoʻi ka piʻi ʻana o Co-SAs/NPs@NC he 0.13 eV, kahi i kōkua ai ma hope o ka hoʻokomo ʻia ʻana o NP, ʻo ka adsorption o nā ʻāpana HCOO* e ka ʻōnaehana uila i hoʻololi ʻia o CoN2C2 e hana ʻia. Hōʻike ka ʻokoʻa o ka nui o ka hoʻouka ʻana i kahi ao electron nui a puni ka poloka CoN2C2 a me ka nanoparticle, e hōʻike ana i kahi pilina ikaika ma waena o lākou ma muli o ka hoʻololi electron. I hui pū ʻia me ka nānā ʻana o ka hoʻouka ʻana o Bader, ua ʻike ʻia ua nalowale ʻo Co i hoʻopuehu ʻia me ka atomically i 1.064e ma Co-SA/NPs@NC a me 0.796e ma Co SA (Kiʻi S44). Hōʻike kēia mau hopena i ka hoʻohui ʻana o nā nanoparticles e alakaʻi i ka hoʻopau ʻana o ka electron i nā pūnaewele Co, e hopena ana i ka piʻi ʻana o ka valence Co, kahi e kūlike me nā hopena XPS (Kiʻi 6c). Ua kālailai ʻia nā ʻano pilina Co-O o ka adsorption HCOO ma luna o Co-SAs/NPs@NC a me Co SA ma ka helu ʻana i ka hui Hamiltonian orbital crystalline (COHP)63. E like me ka mea i hōʻike ʻia ma ke Kiʻi 6 d, ʻo nā waiwai maikaʻi ʻole a me nā waiwai maikaʻi ʻole o -COHP e pili ana i ke kūlana antibonding a me ke kūlana nakinaki, kēlā me kēia. Ua loiloi ʻia ka ikaika o ka pilina o Co-O i adsorbed ʻia e HCOO (Co-carbonyl O HCOO*) ma ka hoʻohui ʻana i nā waiwai -COHP, ʻo ia hoʻi he 3.51 a me 3.38 no Co-SAs/NPs@NC a me Co-SA, kēlā me kēia. Ua hōʻike pū ka adsorption HCOOH i nā hopena like: ʻo ka piʻi ʻana o ka waiwai integral o -COHP ma hope o ka doping nanoparticle e hōʻike ana i ka piʻi ʻana o ka pilina Co-O, no laila e hoʻolaha ana i ka hoʻāla ʻana o HCOO a me HCOOH (Kiʻi S45).
ʻO ke ʻano hana lattice Co-SA/NPs@NC-950. b PDOS Co-SA/NP@NC-950 a me Co SA. c 3D isosurface o ka ʻokoʻa o nā densities charge o ka adsorption HCOOH ma Co-SA/NPs@NC-950 a me Co-SA. (d) pCOHP o nā pilina Co-O i adsorbed ʻia e HCOO ma Co-SA/NPs@NC-950 (hema) a me Co-SA (ʻākau). e Ke ala hana o ka dehydrogenation HCOOH ma Co-SA/NPs@NC-950 a me Co-SA.
I mea e hoʻomaopopo maikaʻi ai i ka hana dehydrogenation kiʻekiʻe o Co-SA/NPs@NC, ua hoʻoholo ʻia ke ala hopena a me ka ikehu. Ma ke ʻano kikoʻī, pili ka dehydrogenation FA i ʻelima mau ʻanuʻu, me ka hoʻololi ʻana o HCOOH i HCOOH*, HCOOH* i HCOO* + H*, HCOO* + H* i 2H* + CO2*, 2H* + CO2* i 2H* + CO2, a me 2H* ma H2 (Kiʻi 6e). ʻOi aku ka haʻahaʻa o ka ikehu adsorption o nā molekala waikawa formic ma ka ʻili catalyst ma o ka oxygen carboxylic ma mua o ka oxygen hydroxyl (Nā Kiʻi S46 a me S47). Ma hope mai, ma muli o ka ikehu haʻahaʻa, makemake nui ka adsorbate i ka ʻoki ʻana o ka pilina OH e hana i ka HCOO* ma mua o ka ʻoki ʻana o ka pilina CH e hana i ka COOH*. I ka manawa like, hoʻohana ʻo HCOO* i ka adsorption monodentate, kahi e paipai ai i ka haki ʻana o nā pilina a me ke kūkulu ʻana o CO2 a me H2. Ua kūlike kēia mau hopena me ke alo o kahi piko νas(OCO) ma ka DRIFT in situ, e hōʻike hou ana e hana ʻia ka hoʻohaʻahaʻa ʻana o FA ma o ke ala formate i kā mākou noiʻi. He mea nui e hoʻomaopopo e like me nā ana KIE, ʻoi aku ka kiʻekiʻe o ka pale ikehu hopena o ka dissociation CH ma mua o nā ʻanuʻu hopena ʻē aʻe a hōʻike i kahi RDS. ʻO ka pale ikehu o ka ʻōnaehana catalyst Co-SAs/NPs@NC kūpono he 0.86 eV haʻahaʻa ma mua o Co-SA (1.2 eV), kahi e hoʻomaikaʻi nui ai i ka pono dehydrogenation holoʻokoʻa. ʻO ka mea nui, ʻo ke alo o nā nanoparticles e hoʻoponopono i ka ʻōnaehana uila o nā wahi coactive i hoʻopuehu ʻia e ka atomically, kahi e hoʻonui hou ai i ka adsorption a me ka hoʻāla ʻana o nā waena, no laila e hoʻohaʻahaʻa ana i ka pale hopena a me ka hoʻolaha ʻana i ka hana hydrogen.
I ka hōʻuluʻulu manaʻo, ke hōʻike nei mākou no ka manawa mua e hiki ke hoʻomaikaʻi nui ʻia ka hana catalytic o nā mea hoʻouluulu hana hydrogen ma o ka hoʻohana ʻana i nā mea me nā kikowaena monometallic i hoʻolaha nui ʻia a me nā nanoparticles liʻiliʻi. Ua hōʻoia ʻia kēia manaʻo e ka synthesis o nā mea hoʻouluulu metala hoʻokahi i hoʻokumu ʻia me ka cobalt i hoʻololi ʻia me nā nanoparticles (Co-SAs/NPs@NC), a me nā mea pili me nā kikowaena metala hoʻokahi wale nō (CoN2C2) a i ʻole Co NPs. Ua hoʻomākaukau ʻia nā mea āpau e kahi ʻano pyrolysis hoʻokahi-ʻanuʻu maʻalahi. Hōʻike ka loiloi kūkulu ʻana ʻo ka mea hoʻouluulu maikaʻi loa (Co-SAs/NPs@NC-950) he mau ʻāpana CoN2C2 i hoʻopuehu ʻia me nā atomically a me nā nanoparticles liʻiliʻi (7-8 nm) i hoʻohui ʻia me ka nitrogen a me ke kalapona e like me ka graphite. Loaʻa iā ia ka huahana kinoea maikaʻi loa a hiki i 1403.8 ml g-1 h-1 (H2:CO2 = 1.01:1), H2 a me ke koho ʻana o CO o 99.96% a hiki ke mālama i ka hana mau no kekahi mau lā. ʻOi aku ka hana o kēia mea hoʻouluulu ma mua o ka hana o kekahi mau mea hoʻouluulu Co SA a me Pd/C ma 4 a me 15 mau manawa, kēlā me kēia. Hōʻike nā hoʻokolohua DRIFT In situ i ka hoʻohālikelike ʻia me Co-SA, hōʻike ʻo Co-SAs/NPs@NC-950 i ka adsorption monodentate ikaika o HCOO*, he mea nui ia no ke ala formate, a hiki i nā nanoparticles dopant ke hoʻolaha i ka hoʻāla ʻana o HCOO* a me ka wikiwiki ʻana o C–H. Ua ʻike ʻia ka ʻoki ʻana o ka pilina ʻo RDS. Hōʻike nā helu kumumanaʻo e hoʻonui ka doping Co NP i ke kikowaena d-band o nā ʻātoma Co hoʻokahi ma 0.13 eV ma o ka launa pū ʻana, e hoʻonui ana i ka adsorption o HCOOH* a me nā waena HCOO*, a laila e hōʻemi ana i ka pale hopena mai 1.20 eV no Co SA a i 0 .86 eV. ʻO ia ke kuleana no ka hana koʻikoʻi.
Ma ke ʻano ākea, hāʻawi kēia noiʻi i nā manaʻo no ka hoʻolālā ʻana i nā mea hoʻoulu metala hoʻokahi-ʻātoma hou a hoʻolaha i ka ʻike pehea e hoʻomaikaʻi ai i ka hana catalytic ma o ka hopena synergistic o nā kikowaena metala o nā nui like ʻole. Manaʻo mākou e hiki ke hoʻonui maʻalahi ʻia kēia ʻano hana i nā ʻōnaehana catalytic ʻē aʻe.
Ua kūʻai ʻia ʻo Co(NO3)2 6H2O (AP, 99%), Zn(NO3)2 6H2O (AP, 99%), 2-methylimidazole (98%), methanol (99.5%), propylene carbonate (PC, 99%) ethanol (AR, 99.7%) mai McLean, Kina. Ua kūʻai ʻia ka waikawa Formic (HCOOH, 98%) mai Rhawn, Kina. Ua hoʻohana pololei ʻia nā reagents a pau me ka ʻole o ka hoʻomaʻemaʻe hou ʻana, a ua hoʻomākaukau ʻia ka wai ultrapure me ka hoʻohana ʻana i kahi ʻōnaehana hoʻomaʻemaʻe ultrapure. Ua kūʻai ʻia ʻo Pt/C (5% mass loading) a me Pd/C (5% mass loading) mai Sigma-Aldrich.
Ua hoʻokō ʻia ka hana ʻana o nā nanocrystals CoZn-ZIF ma muli o nā ʻano hana mua me kekahi mau hoʻololi23,64. ʻO ka mea mua, ua hui pū ʻia he 30 mmol Zn(NO3)2·6H2O (8.925 g) a me 3.5 mmol Co(NO3)2·6H2O (1.014 g) a ua hoʻoheheʻe ʻia i loko o 300 ml o ka methanol. A laila, ua hoʻoheheʻe ʻia he 120 mmol o 2-methylimidazole (9.853 g) i loko o 100 ml o ka methanol a hoʻohui ʻia i ka hopena i luna. Ua hoʻoulu ʻia ka hui ʻana ma ka mahana o ka lumi no 24 mau hola. ʻO ka hope, ua hoʻokaʻawale ʻia ka huahana ma ka centrifugation ma 6429 g no 10 min a holoi pono ʻia me ka methanol ʻekolu manawa. Ua hoʻomaloʻo ʻia ka pauka hopena i loko o ka vacuum ma 60°C i ka pō ma mua o ka hoʻohana ʻana.
No ka hana ʻana i nā Co-SAs/NPs@NC-950, ua hoʻoheheʻe ʻia ka pauka CoZn-ZIF maloʻo ma 950 °C no 1 hola i loko o ke kahe kinoea o 6% H2 + 94% Ar, me ka helu hoʻomehana o 5 °C/min. A laila ua hoʻomaʻalili ʻia ka laʻana i ka mahana o ka lumi e loaʻa ai ʻo Co-SA/NPs@NC-950. No Co-SAs/NPs@NC-850 a i ʻole Co-SAs/NPs@NC-750, ua hoʻololi ʻia ka mahana pyrolysis i 850 a me 750 °C, kēlā me kēia. Hiki ke hoʻohana ʻia nā laʻana i hoʻomākaukau ʻia me ka ʻole o ka hana hou ʻana, e like me ke kālai ʻakika.
Ua hana ʻia nā ana ʻana o ka TEM (transmission electron microscopy) ma kahi microscope "cube" Thermo Fisher Titan Themis 60-300 i lako me kahi mea hoʻoponopono aberration kiʻi a me kahi aniani hoʻopili probe 300 kV. Ua hana ʻia nā hoʻokolohua HAADF-STEM me ka hoʻohana ʻana i nā microscope FEI Titan G2 a me FEI Titan Themis Z i lako me nā probes a me nā mea hoʻoponopono kiʻi, a me nā mea ʻike ʻehā ʻāpana DF4. Ua loaʻa pū nā kiʻi palapala ʻāina elemental EDS ma kahi microscope FEI Titan Themis Z. Ua hana ʻia ka loiloi XPS ma kahi spectrometer photoelectron X-ray (Thermo Fisher model ESCALAB 250Xi). Ua hōʻiliʻili ʻia nā spectra XANES a me EXAFS Co K-edge me ka hoʻohana ʻana i kahi papa XAFS-500 (China Spectral Instruments Co., Ltd.). Ua hoʻoholo ʻia ka ʻike Co e ka spectroscopy absorption atomic (AAS) (PinAAcle900T). Ua hoʻopaʻa ʻia nā spectra diffraction X-ray (XRD) ma kahi diffractometer X-ray (Bruker, Bruker D8 Advance, Kelemānia). Ua loaʻa nā isotherms adsorption nitrogen me ka hoʻohana ʻana i kahi mea hana adsorption kino (Micromeritics, ASAP2020, USA).
Ua hoʻokō ʻia ka hopena dehydrogenation i loko o kahi lewa argon me ka ea i wehe ʻia e like me ke ʻano maʻamau o Schlenk. Ua hoʻoneʻe ʻia ka ipu hana a hoʻopiha hou ʻia me ka argon i 6 mau manawa. E hoʻā i ka lako wai condenser a hoʻohui i ka catalyst (30 mg) a me ka solvent (6 ml). E hoʻomehana i ka ipu i ka mahana i makemake ʻia me ka hoʻohana ʻana i ka thermostat a ʻae iā ia e kaulike no 30 mau minuke. A laila ua hoʻohui ʻia ka waikawa formic (10 mmol, 377 μL) i ka ipu hana ma lalo o ka argon. E hoʻohuli i ka valve burette ʻekolu ala e hoʻohaʻahaʻa i ke kaomi o ka reactor, e pani hou, a hoʻomaka e ana i ka nui o ke kinoea i hana ʻia me ka hoʻohana ʻana i kahi burette manual (Kiʻi S16). Ma hope o ka manawa e pono ai no ka hoʻopau ʻana o ka hopena, ua hōʻiliʻili ʻia kahi laʻana kinoea no ka nānā ʻana o GC me ka hoʻohana ʻana i kahi syringe paʻa kinoea i hoʻomaʻemaʻe ʻia me ka argon.
Ua hana ʻia nā hoʻokolohua DRIFT In situ ma kahi spectrometer Fourier transform infrared (FTIR) (Thermo Fisher Scientific, Nicolet iS50) i lako me kahi mea ʻike mercury cadmium telluride (MCT). Ua kau ʻia ka pauka catalyst i loko o kahi cell reaction (Harrick Scientific Products, Praying Mantis). Ma hope o ka mālama ʻana i ka catalyst me ke kahawai o Ar (50 ml/min) ma ka mahana o ka lumi, ua hoʻomehana ʻia ka laʻana i kahi mahana i hāʻawi ʻia, a laila hoʻolapalapa ʻia me Ar (50 ml/min) i loko o kahi hopena HCOOH a ninini ʻia i loko o ka cell reaction in-situ. no ka hopena. Hoʻohālike i nā kaʻina hana catalytic heterogeneous. Ua hoʻopaʻa ʻia nā spectra infrared ma nā manawa mai 3.0 kekona a i 1 hola.
Hoʻohana ʻia ʻo HCOOH, DCOOH, HCOOD a me DCOOD ma ke ʻano he substrates i loko o ka propylene carbonate. Pili nā kūlana i koe i ke kaʻina hana dehydrogenation HCOOH.
Ua hana ʻia nā helu ʻana o nā kumumanaʻo mua me ka hoʻohana ʻana i ke kahua kumumanaʻo hana density i loko o ka pūʻolo hoʻohālike Vienna Ab initio (VASP 5.4.4) 65,66. Ua hoʻohana ʻia kahi cell superunit me kahi ʻili graphene (5 × 5) me kahi ana transverse o kahi 12.5 Å ma ke ʻano he substrate no CoN2C2 a me CoN2C2-Co6. Ua hoʻohui ʻia kahi mamao vacuum ma mua o 15 Å e pale aku i ka launa pū ʻana ma waena o nā papa substrate e pili ana. Ua wehewehe ʻia ka launa pū ʻana ma waena o nā ions a me nā electrons e ke ʻano o ka nalu amplified projected (PAW) 65,67. Ua hoʻohana ʻia ka hana Perdue-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) me ka hoʻoponopono van der Waals i hāpai ʻia e Grimm 68,69. ʻO nā pae hoʻohālikelike no ka ikehu holoʻokoʻa a me ka ikaika he 10−6 eV/atom a me 0.01 eV/Å. Ua hoʻonohonoho ʻia ka ʻoki ikehu ma 600 eV me ka hoʻohana ʻana i kahi Monkhorst-Pack 2 × 2 × 1 K-point grid. ʻO ka pseudopotential i hoʻohana ʻia ma kēia kumu hoʻohālike ua kūkulu ʻia mai ka hoʻonohonoho uila i loko o ke kūlana C 2s22p2, ke kūlana N 2s22p3, ke kūlana Co 3d74s2, ke kūlana H 1 s1, a me ke kūlana O 2s22p4. Ua helu ʻia ka ikehu adsorption a me ka ʻokoʻa o ka nui o ka electron ma ka unuhi ʻana i ka ikehu o ke ʻano kinoea a me nā ʻano ʻili mai ka ikehu o ka ʻōnaehana adsorbed e like me nā hiʻohiʻona adsorption a i ʻole interface70,71,72,73,74. Hoʻohana ʻia ka hoʻoponopono ikehu manuahi ʻo Gibbs e hoʻololi i ka ikehu DFT i ka ikehu manuahi ʻo Gibbs a noʻonoʻo i nā hāʻawi haʻalulu i ka entropy a me ka ikehu zero point75. Ua hoʻohana ʻia ke ʻano piʻi kiʻi-nudging elastic band (CI-NEB) e ʻimi i ke kūlana hoʻololi o ka hopena76.
Hoʻokomo ʻia nā ʻikepili āpau i loaʻa a kālailai ʻia i ka wā o kēia haʻawina i loko o ka ʻatikala a me nā mea kōkua a i ʻole e loaʻa mai ka mea kākau pili ma ke noi kūpono. Hāʻawi ʻia ka ʻikepili kumu no kēia ʻatikala.
Loaʻa nā code āpau i hoʻohana ʻia i nā simulations e hele pū ana me kēia ʻatikala mai nā mea kākau pili ma ke noi.
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