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Di divɛlɔpmɛnt fɔ haydrojɛn tɛnkɔlɔji dɛn de na di at fɔ di grɛn ikɔmi. As prɛkɔndishɔn fɔ riliys haydrojɛn stɔrɔj, aktiv ɛn stebul katalis fɔ di haydrojɛneshɔn (di)haydrojɛneshɔn riakshɔn nid fɔ de. Te naw, na di we aw pipul dɛn de yuz dia dia valyu tin dɛn na dis eria. Hia, wi prכpos wan nכvel lכw-kכst kכbalt-bεys katalis (Co-SAs/NPs@NC) we hεli distributed singl-mεtal sayt dεm de sinagεstikli kכpl wit fayn nanopartikl dεm fכ achyv efyushכn fכmik asid dεhaydrojenεshכn. Yuz di bes matirial of atomically dispersed CoN2C2 units en encapsulated nanoparticles of 7-8 nm saiz, yuz propylene carbonate as solvent, wan ekselent gas prodakshon of 1403.8 ml g-1 h-1 bin get, en no loss bin de afta 5 saikl. aktiviti, we 15 tεm bεtε pas kכmεshכnal Pd/C. in situ assay εkspεriεns sho se, kכmpεr to rilayt singl mεtal atכm εn nanopartikl katalis, Co-SAs/NPs@NC de εnhans di adsכpshכn εn aktibכshכn fכ di ki monodentate intamεdiεt HCOO*, we de protεkt sכbsεkvεnt CH bכnd klivεj. Tiorikal kכlkyulshכn sho se intagrεshכn fכ kobalt nanopartikl dεm de promuot di kכnvכshכn fכ di d-band sεntr fכ wan singl Co atכm insay wan aktv sayt, we de εnhans di kכpl bitwin di kכbכnayl O fכ di HCOO* intamεdiεt εn di Co sεntr, we de lכs di enεji barεri.
Dɛn kin tek haydrojɛn as impɔtant ɛnaji kyaria fɔ di kɔrɛnt glob ɔl ɛnaji transishɔn ɛn i kin bi wan impɔtant drayva fɔ ajɔst di kabɔn nyutraliti1. Bikɔs ɔf in fizik prɔpati dɛm lɛk flammabiliti ɛn lɔw density, sef ɛn efishɔnal stɔrɔj ​​ɛn transpɔt ɔf haydrojɛn na di men tin dɛm fɔ riliys di haydrojɛn ikɔmi2,3,4. Dɛn dɔn prɔpos likwid ɔrganik haydrojɛn kyaria (LOHC), we de kip ɛn rilis haydrojɛn tru kemikal riakshɔn, as sɔlvushɔn. we yu kompare to mכlikul haydrojεn, dεn kayn tin dεm ya (mεtanכl, toluεn, dibεnzyltoluεn, εtk) izi εn i izi fכ hεndl5,6,7. pan difrεn tradishכnal LOHC dεm, fכmik asid (FA) gεt rili lכw tכksisiti (LD50: 1.8 g/kg) εn H2 kapasiti fכ 53 g/L כ 4.4 wt%. notably, FA na di onli LOHC we kin stכr εn rilis haydrojεn כnda mild kכndishכn insay di prεsεns fכ fayn katalis, so i nכ nid big εksternal εnεji inputs1,8,9. infakt, plεnti nכbul mεtal katalis dεn dכn divεlכp fכ di dihaydrojenεshכn fכ fכmik asid, fכ egzampl, paladyכm-bεys katalis dεm de 50-200 tεm mכr aktv pas inkεnsiv mεtal katalis dεm10,11,12. Bɔt if yu tek tɛm tink bɔt di kɔst fɔ aktiv mɛtal dɛn, fɔ ɛgzampul, paladiɔm dia pas 1000 tɛm.
Cobalt, Di sכch fכ hεli aktv εn stebul hεtεrojεnik bεs mεtal katalis dεm de kכntinyu fכ atrak di intres fכ plεnti risach pipul dεm na akademi εn industri13,14,15.
Pan ɔl we dɛn dɔn divɛlɔp inɛkpɛnsiv katalis dɛn we dɛn bayz pan Mo ɛn Co, ɛn bak nanokatalyst dɛn we dɛn mek frɔm nobul/bɛs mɛtal alɔy,14,16 fɔ FA dihaydrojɛneshɔn, dɛn smɔl smɔl dɛaktiveshɔn we dɛn de du di riakshɔn nɔ go ebul fɔ avɔyd bikɔs ɔf di ɔkupeshɔn fɔ aktiv sayt dɛn fɔ mɛtal, CO2, ɛn H2O bay protɔn dɛn. כ fכmat anכn dεm (HCOO-), FA kכntaminεshכn, patikyula agregεshכn εn posεbul CO pכyzin17,18. Wi ɛn ɔda pipul dɛn nɔ tu te yet we dɛn sho se singl-atɔm katalis (SAC) wit ayli dispɛrs CoIINx sayt dɛn as aktiv sayt dɛn de impruv di riaktiviti ɛn asid rɛsistɛns fɔ fɔmik asid dihaydrojɛneshɔn kɔmpia to nanopartikul dɛn17,19,20,21,22,23,24. insay dεn Co-NC mεtirial dεm ya, N atכm dεm de sav as mεjכr sayt dεm fכ protεkt FA diprotoneshכn we dεn de εnhans strכkchכral stεbiliti tru kכdכnayshכn wit di sεntrial Co atכm, we Co atכm dεm de gi H adsכpshכn sayt dεm εn protεkt CH22 scission, 25,26. כnכfכs, di aktvכti εn stεbiliti fכ dεn katalis ya stil fa frכm mכdan homojεnik εn hεtεrojεnik nכbul mεtal katalis dεm (Fig. 1) 13 .
Ɛkses ɛnaji frɔm rinuɔbal sɔs dɛm lɛk solar ɔ briz kin kɔmɔt bay ilɛktrɔlaysis fɔ wata. di haydrojen we dεn prodyuz kin stכr yuz LOHC, wan likwid we in haydrojεnεshכn εn dihaydrojenεshכn kin rivashכn. Insay di dihaydrojɛneshɔn stɛp, di wangren tin we de mek na haydrojɛn, ɛn di likwid we de kɛr di tin kin go bak to in ɔrijinal stet ɛn dɛn kin gɛt haydrojɛn bak. As tɛm de go, dɛn kin yuz haydrojɛn fɔ mek gas steshɔn dɛn, batri dɛn, bildin dɛn we dɛn kin yuz fɔ mek industri, ɛn ɔda tin dɛn.
rεsεntli, dεn bin ripot se di intrinsik aktiviti fכ spεsifi k SAC dεm kin εnhans insay di prεsεns fכ difrεn mεtal atכm dεm כ adishכnal mεtal sayt dεm we nanopartikl (NP) כ nanoklasta (NC) de gi27,28. dis de opin op possibiliti fכ fכda adsכpshכn εn aktibכshכn fכ di sabstεrayt, εn bak fכ mכduleshכn fכ di jכmetri εn ilektronik strכkchכ fכ monatomik sayt dεm. כl dis mek, sabstεrayt adsכpshכn/aktivεshכn kin optimiz, we de gi bεtε כvala katalytik efyushכn29,30. dis de gi wi di aidia fכ mek aprכpriet katalytik mεtirial dεm wit haybrid aktv sayt dεm. Pan ɔl we impɔtant SAC dɛn dɔn sho big pɔtnɛshɛl insay bɔku bɔku katalitik aplikeshɔn dɛn, dɛn wok fɔ stɔrɔj ​​haydrojɛn, to wi no, nɔ klia. In dis rispek, wi ripot wan versatile en robust strateji fכ di sεntesis כf kobalt-bεys haybrid katalis (Co-SAs/NPs@NCs) we kכnsis כf difayn nanopartikl εn individyual mεtal sεnta. Di optimized Co-SAs/NPs@NC exhibit ekselent fכmik asid dihaydrojeneshכn pεrformεns, we bεtε pas nכn-nobul nanostructured katalis (lεk CoNx, singl kobalt atכm, kobalt@NC εn γ-Mo2N) εn ivin nobul mεtal katalis. In-situ karaktaizεshכn εn DFT kכlkyulεshכn fכ aktv katalis sho se individyual mεtal sayt dεm de sav as aktv sayt, εn di nanopartikl dεm fכ di prεsεnt invεnshכn de εnhans di d-band sεntr fכ Co atכm dεm, promuot adsכpshכn εn aktibכshכn fכ HCOO*, we de lכs di enεji barεri fכ di riakshכn. .
Ziolite imidazolate frameworks (ZIFs) na wel-difain tri-dimenshonal prεkursכr dεm we de gi katalis fכ naytrojen-dכp kabכnas mεtirial (mεtal-NC katalis) fכ sכpכt difrεn tכp mεtal dεm37,38. So, Co(NO3)2 εn Zn(NO3)2 de kam togεda wit 2-methylimidazole insay mεtanכl fכ fכm di kכrεspכndεnt mεtal kכmpleks dεm insay sכlushכn. Afta sεntrifugayshכn εn dryin, CoZn-ZIF bin pyrolyzed pan difrεnt tεmprachכ (750–950 °C) insay wan atmosfεr we 6% H2 εn 94% Ar. As yu si na di figa dכn, di mεtirial dεm we kכmכt gεt difrεn aktv sayt kכntribyushכn dεm εn dεn gi dεm di nem Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 εn Co-SAs/NPs@NC-750 (Figure 2a). ) . sכm spεsifi k εkspεriεns obsכbishכn dεm fכ sכm ki stεp dεm na di sεntesis prכsεs dεn dεtayl insay fכg 1 εn 2. C1-C3. Variable temperature powder X-ray diffraction (VTXRD) bin de du fɔ monitar di evolushɔn fɔ di katalis. afta di payrolisis tεmprachכ rich 650 °C, di XRD patεn chenj bכku bכku wan biכs fכ di kolכpshכn fכ di כda kristכl strכkchכ fכ ZIF (Fig. S4) 39 . As di tεmprachכ de inkrεs mכr, tu brayt pik dεm de apia na di XRD patεn dεm fכ Co-SAs/NPs@NC-850 εn Co-SAs/NPs@NC-750 na 20–30° εn 40–50°, we de riprizent di pik fכ amorphous kabכn (Fig. C5). 40. I fayn fɔ no se na tri karakta pik nɔmɔ dɛn bin si na 44.2°, 51.5° ɛn 75.8°, we na mɛtalik kɔbalt (JCPDS #15-0806), ɛn 26.2°, we de pan grafiti kabɔn (JCPDS # 41-1487). di X-ray spεktrum fכ Co-SAs/NPs@NC-950 sho di prεsεns כf grafayt-lεk εnkapsulεt kכbalt nanopartikl dεm pan di katalis41,42,43,44. Di Raman spɛktrum sho se i tan lɛk se Co-SAs/NPs@NC-950 gɛt strɔng ɛn smɔl D ɛn G pik pas di ɔda sampul dɛn, we sho se i gɛt ay digri pan grafaytayzeshɔn ( Figure S6 ). Apat frɔm dat, Co-SAs/NPs@NC-950 de sho ay Brunner-Emmett-Taylor (BET) sɔfa eria ɛn pore volyum (1261 m2 g-1 ɛn 0.37 cm3 g-1) pas ɔda sampul dɛn ɛn mɔs ZIF dɛn na NC dɛrivativ. matirial (Figure S7 ɛn Tebul S1). Atɔmik absɔpshɔn spɛktroskɔpi (AAS) sho se di kɔbalt kɔntinyu na Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 ɛn Co-SAs/NPs@ na 2.69 wt%, 2.74 % wt. ɛn 2.73% wt. NC-750 rispɛktvɔli (Tɛbul S2). di Zn kכntεnt fכ Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 εn Co-SAs/NPs@NC-750 de inkrεs sכmtεm, we dεn atribyut to di inkrεs rεdukshכn εn volatilayzεshכn fכ Zn yunit dεm. Inkrεs in payrolisis tεmprachכ (Zn, bכyl pכynt = 907 °C) 45.46. Elemental analysis (EA) sho se di pasεnshכn fכ N de dכn wit inkrεs pan pyrolysis tεmprachכ, εn di hכy O kכntεnt kin bi biכs fכ di adsכpshכn fכ mכlikul O2 frכm εkspכzכn to εya. (Tɛbul S3). pan wan sכm kכbalt kכntεnt, nanopartikl dεm εn isolεt kכatכm dεm de kכgεst, we de rεsult in wan siknifikant inkrεs pan katalis aktiviti, lεk aw dεn dכn tכk bכt dכn.
Skematik dayagram fכ di sεntez fכ Co-SA/NPs@NC-T, usay T na di payrolysis tεmprachכ (°C). b TEM imej we dɛn mek. c Imej fɔ Kɔ-SA dɛn/NP dɛn@NC-950 AC-HAADF-STEM. Dɛn mak wan wan Co atɔm dɛn wit rɛd sɛrkɛl dɛn. d EDS Templat Ko-SA/NPs@NC-950.
notably, transmishכn εlektrכn maykroskכpi (TEM) dεn sho di prεsεns כf difrεn kכbalt nanopartikl (NPs) wit wan avεj saiz 7.5 ± 1.7 nm כnli in Co-SA/NPs@NC-950 ( Figures 2 b εn S8). dis nanopartikl dεm de kapsul wit grafayt-layk kabכn we dεn dכp wit naytrojen. Di lat fring spays we na 0.361 ɛn 0.201 nm kɔrɛspɔnd to grafitik kabɔn (002) ɛn mɛtalik Co (111) patikyula dɛn, rispɛktvɔli. Apat frɔm dat, ay-ɛngl aberreshɔn-kɔrɛkt anul dak-fild skan transmishɔn ilɛktron maykroskɔpi (AC-HAADF-STEM) rivɛl se Co NPs insay Co-SAs/NPs@NC-950 bin rawnd bɔku bɔku atɔmik kɔbalt (Fig. 2c). Bɔt na ɔl di atɔmik dispɛrs kɔbalt atɔm dɛn nɔmɔ dɛn bin si pan di sɔpɔt fɔ di ɔda tu sampul dɛn (Fig. S9). Energy dispersive spectroscopy (EDS) HAADF-STEM imej sho yunifom distribyushɔn fɔ C, N, Co ɛn sɛgregɛt Co NP dɛn insay Co-SAs/NPs@NC-950 (Fig. 2d). Ɔl dɛn rizɔlt ya sho se atɔmik dispɛrs Co sɛnta ɛn nanopartikl dɛn we dɛn kapsul insay N-dɔp grafayt-layk kabɔn de saksesful wan atak to NC sabstret dɛn insay Co-SAs/NPs@NC-950, we na ɔl isol mɛtal sɛnta dɛn.
Di valɛns stet ɛn kemikal kɔmpɔzishɔn fɔ di matirial dɛn we dɛn gɛt bin stɔdi bay X-ray fotoɛlektrɔn spɛktroskɔpi (XPS). Di XPS spɛktra fɔ di tri katalis dɛn sho di prɛzɛns fɔ ɛlimɛnt dɛn Co, N, C ɛn O, bɔt Zn bin de nɔmɔ insay Co-SAs/NPs@NC-850 ɛn Co-SAs/NPs@NC-750 (Fig. 2). ). C10). as di payrolisis tεmprachכ de inkrεs, di tכtal naytrojen kכntεnt de dכn as di naytrojen spεshal dεm de bi כnstebul εn dεkכmpכz to NH3 εn NOx gas dεm na hכy tεmprachכ (Tεbul S4) 47 . So, di totכl kabכn kכntεnt sכmtεm inkrεs frכm Co-SAs/NPs@NC-750 to Co-SAs/NPs@NC-850 εn Co-SAs/NPs@NC-950 (Figure S11 εn S12). Di sampul we dɛn payrolayz pan ay tɛmpracha gɛt smɔl pat pan naytrɔjen atɔm dɛn, we min se di amɔnt fɔ NC kyaria dɛn na Co-SAs/NPs@NC-950 fɔ smɔl pas di wan we de na ɔda sampul dɛn. Dis kin mek di kobalt patikyula dɛn strɔng mɔ. Di O 1s spɛktrum sho tu pik C=O (531.6 eV) ɛn C–O (533.5 eV), rispɛktvɔli (Figure S13) 48 . As yu si na Fig 2a, di N 1s spɛktrum kin rizɔlt insay 4 karakta pik dɛn we gɛt piridin naytrɔjen N (398.4 eV), payrɔl N (401.1 eV), grafayt N (402.3 eV) ɛn Co-N (399.2 eV). Co-N bond dεm de insay כl di tri sεmpl dεm, we sho se sכm N atכm dεm kכdכnayt to monomεtal sayt dεm, bכt di kכntribyushכn dεm difrεnt bכku49. Aplikeshɔn fɔ ay payrolisis tɛmpracha kin ridyus di kɔntinyu fɔ Co-N spɛshal frɔm 43.7% insay Co-SA/NPs@NC-750 to 27.0% insay Co-SAs/NPs@NC-850 ɛn Co 17.6%@ NC-950. in -CA/NPs, we kכrεspכnd to inkrεs pan di C kכntεnt (Fig. 3a), we de sho se dεn Co-N kכdכnayshכn nכmba kin chenj εn patli riples bay C50 atכm dεm. di Zn 2p spεktrum sho se dis εlimεnt de prεdominantli insay di fכm Zn2+. (Figure S14) 51. Di spɛktrum fɔ Co 2p de sho tu prominɛnt pik dɛn na 780.8 ɛn 796.1 eV, we dɛn atribyut to Co 2p3/2 ɛn Co 2p1/2, rispɛktvɔli (Figure 3b). We yu kɔmpia am wit Co-SAs/NPs@NC-850 ɛn Co-SAs/NPs@NC-750, di Co-N pik na Co-SAs/NPs@NC-950 de shift to di pɔzitiv sayd, we sho se wan Co atɔm to di sɔfa -SAs/NPs@NC-950 gɛt ay digri pan ɛliktrɔn diplɛshɔn, we de rilizɔt in ay ɔksidɛshɔn stet. i fayn fכ no se na כnli Co-SAs/NPs@NC-950 sho wik pik fכ ziro-valεnt kכbalt (Co0) na 778.5 eV, we pruv di egzistens כf nanopartikl dεm we kכmכt frכm di agregεshכn כf kobalt SA na ay tεmprachכ.
a N 1s ɛn b Co 2p spɛktra fɔ Co-SA/NPs@NC-T. c XANES ɛn d FT-EXAFS spɛktra fɔ Kɔ-K-ɛj fɔ Kɔ-SA dɛn/NPs@NC-950, Kɔ-SA dɛn/NPs@NC-850 ɛn Kɔ-SA dɛn/NPs@NC-750. e WT-EXAFS kɔntɔ plot dɛn fɔ Kɔ-SA dɛn/NPs@NC-950, Kɔ-SA dɛn/NPs@NC-850, ɛn Kɔ-SA dɛn/NPs@NC-750. f FT-EXAFS fitin kεrv fכ Co-SA/NPs@NC-950.
Afta dat, dɛn yuz tɛm-lɔk X-ray absɔpshɔn spɛktroskɔpi (XAS) fɔ analayz di ilɛktronik strɔkchɔ ɛn kɔdineshɔn ɛnvayrɔmɛnt fɔ di Co spɛshal dɛn na di sampul we dɛn pripia. Kobalt valεns stet in Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 εn Co-SAs/NPs@NC-750 Edj strכkchכ we dεn rivεl bay nכmal nia-fild X-ray absכpshכn fכ Co-K edj ( XANES) spεktrum. As yu si na Fig 3c, di absכpshכn nia di edj fכ di tri sεmpl dεm de bitwin di Co εn CoO fכyl dεm, we sho se di valεns stet fכ Co spεshal dεm de frכm 0 to +253. Apat frɔm dat, dɛn bin si wan transishɔn to lɔwa ɛnaji frɔm Co-SAs/NPs@NC-950 to Co-SAs/NPs@NC-850 ɛn Co-SAs/NPs@NC-750, we sho se Co-SAs/ NPs@NC-750 gɛt lɔwa ɔksidɛshɔn stet. rivays ɔda. Akɔdin to di linya kɔmbayn fitin rizɔlt, dɛn ɛstimat di Co valɛns stet fɔ Co-SAs/NPs@NC-950 fɔ bi +0.642, we smɔl pas di Co valɛns stet fɔ Co-SAs/NPs@NC-850 (+1.376). Ko-SA/NP @NC-750 (+1.402) we dɛn kɔl. Dis rizulεt dεm sho se di avεrej כksidεshכn stet fכ kobalt patikyula dεm na Co-SAs/NPs@NC-950 dεn rεdכks bכku, we kכnsist wit di XRD εn HADF-STEM risכlt dεm εn dεn kin εksplen am bay di kכbalt nanopartikl dεm εn singl kobalt. . Co atom 41. Fourier transfכm X-ray absכpshכn fayn strכkchכ (FT-EXAFS) spεktrum fכ di Co K-edj sho se di men pik na 1.32 Å na di Co-N/Co-C shel, we di skata pat fכ mεtal Co -Co de na 2.18 nכmכ insay Co-SAs Å we dεn fכnshכn na /NPs@NC-950 (Fig. 3d). Plɛnti mɔ, di wɛvlɛt transfɔm (WT) kɔntɔ plot sho di maksimal intɛnsity na 6.7 Å-1 we dɛn atribyut to Co-N/Co-C, we na ɔl Co-SAs/NPs@NC-950 sho di maksimal intensiti we dɛn atribyut to 8.8. כda intensiti maksimכm de na Å−1 to di Co–Co bond (Fig. 3e). Apat frɔm dat, EXAFS analisis we di lɛsa du sho se na payrolaysis tɛmpracha we na 750, 850 ɛn 950 °C, di Co-N kɔdineshɔn nɔmba dɛn na bin 3.8, 3.2 ɛn 2.3, rispɛktvɔli, ɛn di Co-C kɔdineshɔn nɔmba dɛn na bin 0. 0.9 ɛn 1.8 (Fig. 3f, S15 ɛn Tebul S1). mכr spεsifi k, di laytst risכlt kin bi atribyut to di prεsεns כf atomically dispersed CoN2C2 yunit dεm εn nanopartikl dεm in Co-SAs/NPs@NC-950. difrεnt frכm dat, insay Co-SAs/NPs@NC-850 εn Co-SAs/NPs@NC-750, na כnli CoN3C εn CoN4 yunit dεm de. i klia se wit inkrεsiv payrolisis tεmprachכ, N atכm dεm na di CoN4 yunit de riples sכmtεm wit C atכm dεm, εn kobalt CA agregεt fכ fכm nanopartikl dεm.
Previously stכdi riakshכn kכndishכn dεn bin yuz fכ stכdi di ifekt כf prεparashכn kכndishכn pan di prכpati dεm fכ difrεn mεtirial dεm (Fig. S16)17,49. As yu si na Fig 4 a, di aktiviti fɔ Co-SAs/NPs@NC-950 rili ay pas di wan fɔ Co-SAs/NPs@NC-850 ɛn Co-SAs/NPs@NC-750. Notis, ɔl di tri pripia Co sɛmpul dɛn sho supia pefɔmɛns kɔmpia to standad kɔmɛshɔnal prɛshɔ mɛtal katalis (Pd/C ɛn Pt/C). Apat fr dat, di Zn-ZIF-8 εn Zn-NC sεmpl dεm bin inaktiv tכwεd fכmik asid dεhaydrojenεshכn, we sho se di Zn patikyula dεm nכto aktv sayt, bכt dεn ifekt pan di aktvכti na nεglijibl. Apat frɔm dat, di aktiviti fɔ Co-SAs/NPs@NC-850 ɛn Co-SAs/NPs@NC-750 bin ɔnda sɛkɔndari payrolaysis na 950°C fɔ 1 awa, bɔt i bin smɔl pas di wan fɔ Co-SAs/NPs@NC-750 . @NC-950 (Fig. S17) we dɛn kɔl S17. Structural characterization of dis matirial sho di prezɛns ɔf Co nanoparticles in di ri-pyrolyzed sampul, bɔt di lɔw spɛsifi k sɔfayz eria ɛn absɛns ɔf grafayt-layk kabɔn rizulta in lɔwa aktiviti kɔmpia to Co-SAs/NPs@NC-950 (Figure S18–S20). Di aktvכti כf sεmpl wit difrεnt amoun כf Co prεkursכr bin kכmpεr bak, wit di hεyest aktvכti we dεn sho na 3.5 mol adishכn (Tεbul S6 εn Fig S21). I klia se di fכmeshכn fכ difrεn mεtal sεntr dεm de infכmeshכn bay di haydrojεn we de insay di payrolaysis atmosfεr εn di payrolaysis tεm. So, ɔda Co-SAs/NPs@NC-950 matirial dɛn bin evalyu fɔ fɔmik asid dihaydrojɛneshɔn aktiviti. Ɔl di matirial dɛn sho se dɛn de du mɔdaret to rili gud wok; כltu, nכn pan dεm nכ bin bεtε pas Co-SAs/NPs@NC-950 (Figure S22 εn S23). di strכkchכral kכntribyushכn fכ di mεtirial sho se wit inkrεs pan di payrolysis tεm, di kכntεnt fכ monoatomik Co-N posishכn dεm de dכn sכmtεm biכs fכ di agregεshכn fכ mεtal atכm dεm insay nanopartikl dεm, we de εksplen di difrεns in aktiviti bitwin sεmpl dεm wit payrolysis tεm we na 100-2000. difrɛn. 0.5 h, 1 h, ɛn 2 h (Figure S24–S28 ɛn Tebul S7).
Graf fɔ gas volyum versus di tɛm we dɛn gɛt di tɛm we dɛn de dihaydrojɛn di fiul asɛmbli dɛn we dɛn de yuz difrɛn katalis dɛn. Riakshɔn kɔndishɔn dɛn: FA (10 mmol, 377 μl), katalis (30 mg), PC (6 ml), Tback: 110 °C, Taktikal: 98 °C, 4 pat b Co-SAs/NPs@NC-950 ( 30 mg), difrɛn sɔlvɛnt dɛn. c Kכmpεreshכn כf gas εvכlyushכn rεt כf hεtεrojεnik katalis in כrganik sכlvεnt dεm na 85–110 °C. d Co-SA/NPs@NC-950 risaykul ɛkspirimɛnt. Riakshɔn kɔndishɔn dɛn: FA (10 mmol, 377 μl), Co-SAs/NPs@NC-950 (30 mg), sɔlvɛnt (6 ml), Tback: 110 °C, Taktikal: 98 °C, ɛni riakshɔn saykl de las wan awa . Erɔ bar dɛn de sho standad dɛvyayshɔn dɛn we dɛn kɔl frɔm tri aktiv tɛst dɛn.
in jεnarכl, di efyushכn fכ FA dihaydrojenεshכn katalis dεm de hεli dipεnd pan di riakshכn kכndishכn dεm, spεshal wan di sכlvεnt we dεn yuz8,49. we yu yuz wata as sכlvεnt, Co-SAs/NPs@NC-950 sho di hεyest initial riakshכn rεt, bכt dεaktivεshכn apin, posisibul biכs fכ protכn כ H2O18 we okyupay di aktv sayt dεm. Tεst כf di katalis in כrganik sכlvεnt lεk 1,4-dayoksan (DXA), n-butyl asetεt (BAC), toluεn (PhMe), triglim εn sayklohεksanכn (CYC) כlso nכ sho nכ improvεmεnt, εn in prכpilin kabכnayt (PC) ) (Fig. 4b εn Tεbul S8). Semweso, aditiv dεm lεk triethylamine (NEt3) כ sכdiכm fכmat (HCCONa) nכ bin gεt nכ fכda pכsitiv ifekt pan katalis pεrformεns (Figure S29). כnda optimal riakshכn kכndishכn, di gas yield rich 1403.8 mL g−1 h−1 (Fig. S30), we bin sכmtεm hכy pas כl di Co katalis dεm we dεn bin ripot bifo (inklud SAC17, 23, 24). Insay difrɛn ɛkspiriɛns dɛn, we dɛn nɔ inklud riakshɔn dɛn na wata ɛn wit fɔmat aditiv, dɛn bin gɛt sɛlɛktiviti we go rich 99.96% fɔ dihaydrojɛneshɔn ɛn dɛhaydreshɔn (Tɛbul S9). di kכlkyul aktibכshכn εnεji na 88.4 kJ/mol, we kכmparabl to di aktibכshכn εnεji fכ nכbul mεtal katalis dεm (Figure S31 εn Tεbul S10).
Apat fr dat, wi kכmpεr wan nכmba כf כda hεtεrojεnik katalis fכ fכmik asid dεhaydrojenεshכn כnda di sem kayn kכndishכn (Fig. 4c, tebul S11 εn S12). As yu si na Fig 3c, di gas prodakshɔn rit fɔ Co-SAs/NPs@NC-950 pas di wan we bɔku pan di hɛtɛrojɛnik bays mɛtal katalis dɛn we dɛn sabi ɛn i 15 ɛn 15 tɛm ay pas di wan we kɔmɛshɔnal 5% Pd/C ɛn 5% Pd/C, rispɛktvɔli. wan tɛm. % Pt/C katalis.
Wan impɔtant tin fɔ ɛni prɛktikal aplikeshɔn fɔ (di)haydrojɛneshɔn katalis na dɛn stebiliti. So, dɛn bin du wan siriɔs risaykul ɛkspiriɛns we dɛn yuz Co-SAs/NPs@NC-950. As yu si na Fig 4 d, di initial aktiviti ɛn selektiviti fɔ di matirial nɔ bin chenj ova fayv kɔnsɛkutiv rɔn (luk bak Tebul S13). Lכng tεm tεst dεm bin kכnεkt εn gas prodakshכn inkrεs linya wan ova 72 awa (Figure S32). Di kobalt kɔntinyu fɔ di yuz Co-SA/NPs@NC-950 na bin 2.5 wt%, we bin rili klos to di wan we di fresh katalis gɛt, we sho se no klia lichin nɔ bin de pan kobalt (Tɛbul S14). No klia kכla chenj כ agregεshכn כf mεtal patikyula dεm bin obsεv bifo εn afta di riakshכn ( Figure S33 ). AC-HAADF-STEM ɛn EDS ɔf matirial dɛn we dɛn aplay insay lɔng tɛm ɛkspiriɛns sho ritɛnshɔn ɛn yunifom dispershɔn fɔ atɔmik dispershɔn sayt ɛn nɔ signifyant strɔkchɔral chenj (Figure S34 ɛn S35). Di kכntribyushכn pik dεm fכ Co0 εn Co-N stil de insay XPS, we de pruv di kכ-εgzistεns fכ Co NP dεm εn individyual mεtal sayt dεm, we de kכnfכm bak di stεbiliti fכ di Co-SAs/NPs@NC-950 katalis (Figure S36).
Fכ no di mכst aktiv sayt dεm we rispansabl fכ fכmik asid dεhaydrojenεshכn, dεn bin pripia sεlekt mεtirial dεm wit כnli wan mεtal sεntr (CoN2C2) כ Co NP bays pan stכdi dεm we bin dכn bifo17. di כda fכmik asid dεhaydrojeneshכn aktvכti we dεn obsεv כnda di sem kכndishכn dεm na Co-SAs/NPs@NC-950 > Co SA > Co NP (Tεbul S15), we sho se atכmik dispersed CoN2C2 sayt dεm de mכr aktv pas NP dεm . di riakshכn kεnεtiks sho se haydrojεn εvכlyushכn de fala fכs כda riakshכn kεnεtiks, bכt di sכlכp dεm fכ sεvεra kכv dεm na difrεn kכbalt kכntεnt dεm nכ de di sem, we sho se di kεnεtiks nכ de dipכnt nכto כnli pan fכmik asid, bכt i de dipכnt bak pan di aktv sayt (Fig. 2). C37). Fɔda kaynɛtik stɔdi dɛn sho se, we dɛn gi di absɛns ɔf kobalt mɛtal pik dɛn na ɛkstrem rayt difrakshɔn analisis, dɛn fain se di kaynɛtik ɔda fɔ di riakshɔn in tayms ɔf kobalt kɔntinyu fɔ bi 1.02 na lɔwa lɛvɛl (lɛs dan 2.5%), we sho se wan ɔlmost yunifom distribyushɔn fɔ monoatɔmik kɔbalt sɛnta dɛn. men. aktiv sayt (fig. S38 ɛn S39). we di kכntεnt fכ Co patikyula dεm rich 2.7%, r de inkrεs wan wan, we de sho se di nanopartikl dεm de intarakt fayn wit wan wan atכm dεm fכ gεt hכy aktiviti. as di kכntεnt fכ di Co patikyula dεm de inkrεs mכr, di kכv de bi nכnlayn, we de sho se di nכmba fכ di nanopartikl dεm de inkrεs εn di dכn pan di monatomik posishכn dεm. So, di improv LC dihaydrojeneshכn pεrformεns fכ Co-SA/NPs@NC-950 rizulεt frכm di kכpεraytiv bihayv כf individyual mεtal sayt dεm εn nanopartikl dεm.
Wan in-dip stכdi bin kכriכnt yuz in situ difεs rεflεktεns Fourier transfכm (in situ DRIFT) fכ aydentify riakshכn intamεdiεt dεm insay di prכsεs. Afta we dɛn ɔt di sampul dɛn to difrɛn riakshɔn tɛmpracha afta dɛn ad fɔmik asid, dɛn si tu sɛt dɛn fɔ frikshɔn (Fig. 5a). Tri kכntribyushכn pik dεm fכ HCOOH* de apin na 1089, 1217 εn 1790 cm-1, we dεn atribyut to di כt-כf-plεn CH π (CH) strεch vaybrεshכn, CO ν (CO) strεch vaybrεshכn εn C=O ν (C=O) strεch vaybrεshכn, 54, 55 rispεktivli . Wan ɔda sɛt fɔ pik dɛn na 1363 ɛn 1592 cm-1 kɔrɛspɔnd to di simɛtrik OCO vaybreshɔn νs(OCO) ɛn di asimɛtrik OCO strɛch vaybreshɔn νas(OCO)33.56 HCOO*, rispɛktvɔli. as di riakshכn de go, di rilitiv pik dεm fכ HCOOH* εn HCOO* de wik sכmtεm. jεnarali, di dεkompozishכn fכ fכmik asid involv tri men stεp dεm: (I) adsכpshכn fכ fכmik asid na aktv sayt dεm, (II) fכ pul H tru di fכmat כ kכbכksilayt path, εn (III) kכmbaynshכn fכ tu adsכb H fכ prodyuz haydrojεn. HCOO* εn COOH* na ki intamεdiεt dεm fכ disayd di fכmat כ kכbכksilayt path dεm, rispεktivli57. insay wi katalytik sistεm, na di kכntribyushכn HCOO* pik nכmכ bin apia, we sho se di dεkomposishכn fכ fכmik asid de apin כnli tru di fכmik asid path58. Similar obsכbishכn dεn bin mek pan lכw tεmprachכ 78 °C εn 88 °C (fig. S40).
In situ DRIFT spɛktra fɔ HCOOH dihaydrojɛneshɔn pan wan Co-SAs/NPs@NC-950 ɛn b Co SAs. Di lɛjɛnd de sho di tɛm dɛn we dɛn kin riak na di sayt. c Dynamics of gas volyum we dɛn gɛt we dɛn yuz difrɛn aysɔtop lɛbɛlin rijen dɛn. d Kinetik isotop ifekt data.
Similar in situ DRIFT experiments wεn kכriכnt pan di rilayt mεtirial Co NP εn Co SA fכ stכdi di sinagεstik ifekt in Co-SA/NPs@NC-950 ( Figures 5 b εn S41). di tu mεtirial dεm sho di sem kayn tren, bכt di kכntribyushכn pik dεm fכ HCOOH* εn HCOO* dεn shift sכmtεm, we sho se di introdכkshכn fכ Co NP dεm de chenj di ilektronik strכkchכ fכ di monoatomik sεntr. wan kכntribyushכn νas(OCO) pik de apin insay Co-SAs/NPs@NC-950 εn Co SA bכt nכto insay Co NP dεm, we de sho fכs se di intamεdiεt we fכm we dεn ad fכmik asid na monodentate fכmik asid pεrpindikul to di plen sכlt sεf. εn i de adsכp pan SA as di aktv sayt 59 . I fayn fɔ no se dɛn bin si wan signifyant inkris pan di vaybreshɔn dɛn na di karakta pik π(CH) ɛn ν(C = O), we i tan lɛk se i mek di HCOOH* distɔrshɔn ɛn i mek di riakshɔn izi. As a rizulyt, di kכntribyushכn pik dεm fכ HCOOH* εn HCOO* in Co-SAs/NPs@NC kכlכsכl disappear afta 2 min riakshɔn, we fast pas di wan fכ monomεtal (6 min) εn nanopartikl-bεys katalis (12 min). . כl dis rizulεt dεm kכnfכm se nanopartikl dכping de εnhans di adsכpshכn εn aktibכshכn fכ intamεdiεt dεm, we de aksεlεrat di riakshכn dεm we dεn prכpos oba.
Fכ fכs analכz di riakshכn path εn dεtεmin di rεt dεterminin stεp (RDS), di KIE ifekt bin kכriכnt insay di prεsεns כf Co-SAs/NPs@NC-950. Na ya, dɛn de yuz difrɛn fɔmik asid aysɔtop dɛn lɛk HCOOH, HCOOD, DCOOH ɛn DCOOD fɔ KIE stɔdi. As yu si na Fig 5c, di dihaydrojeneshכn rεt de dכn insay dis כda: HCOOH > HCOOD > DCOOH > DCOOD. Apat frɔm dat, di valyu dɛn we dɛn kɔl KHCOOH/KHCOOD, KHCOOH/KDCOOH, KHCOOD/KDCOOD ɛn KDCOOH/KDCOOD na bin 1.14, 1.71, 2.16 ɛn 1.44, rispɛktvɔli (Fig. 5d). so, CH bond klivεj in HCOO* de sho kH/kD valyu >1.5, we de sho se i gεt mεjכr kinetik ifekt60,61, εn i tan lεk se i de riprizent di RDS fכ HCOOH dihaydrojenεshכn pan Co-SAs/NPs@NC-950.
Apat frɔm dat, dɛn bin du DFT kɔlkyulɛshɔn fɔ ɔndastand di ifɛkt we doped nanopartikl dɛn gɛt pan di intrinsik aktiviti fɔ Co-SA. Di Co-SAs/NPs@NC ɛn Co-SA mɔdel dɛn bin kɔnstrɔk bays pan di ɛkspiriɛns dɛn we dɛn sho ɛn di wok dɛn we dɛn bin dɔn du bifo (Fig. 6a ɛn S42)52,62. Afta jɔyometrik ɔptimayzeshɔn, dɛn bin aydentify smɔl Co6 nanopartikl dɛn (CoN2C2) we de kɔ-ɛgzistin wit monoatɔmik yunit dɛn, ɛn dɛn bin disayd se di Co-C ɛn Co-N bond lɔng dɛn na Co-SA/NPs@NC na 1.87 Å ɛn 1.90 Å, rispɛktvɔli. , we kɔnsistɛn wit di XAFS rizɔlt dɛn. Di kalkyul patɛl density ɔf stet (PDOS) sho se singl Co mɛtal atɔm ɛn nanopartikl kɔmpɔzit (Co-SAs/NPs@NC) de sho ay haybridayzeshɔn nia di Fɛmi lɛvɛl kɔmpia to CoN2C2, we de rilizɔt HCOOH. di dεkompoz εlektrכn tכnfכs de mכr efyushכn ( Figure 6b εn S43). Di kɔrɛspɔndɛns d-band sɛnta dɛn fɔ Co-SAs/NPs@NC ɛn Co-SA bin kɔlkul fɔ bi -0.67 eV ɛn -0.80 eV, rispɛktvɔli, bitwin we di inkris fɔ Co-SAs/NPs@NC na bin 0.13 eV, we kɔntribyut se afta di introdɔkshɔn fɔ NP, di adsɔpshɔn fɔ HCOO* patikyula dɛn bay di adapt ilɛktronik strɔkchɔ fɔ CoN2C2 de apin. di difrεns in chaj dεnsiti sho wan big εlektrכn klawd rawnd di CoN2C2 blכk εn di nanopartikl, we de sho se strכng intarakshכn bitwin dεm bikoz fכ εlektrכn εkshεnj. Kɔmbayn wit Bader chaj analisis, dɛn fain se atɔmik dispɛrs Co lɔs 1.064e insay Co-SA/NPs@NC ɛn 0.796e insay Co SA ( Figure S44 ). dis rizulεt dεm sho se di intagrεshכn fכ nanopartikl dεm de lid to εlektrכn dεplεshכn fכ Co sayt dεm, we de rεsult in inkrεs pan Co valεns, we kכnsist wit di XPS risכlt (Fig. 6c). Di Co-O intarakshɔn kwaliti dɛn fɔ HCOO adsɔpshɔn pan Co-SAs/NPs@NC ɛn Co SA bin analayz bay we dɛn kɔl di kristalin ɔrbital Hamiltonian grup (COHP)63. as yu si na di pikchכ 6 d, nεgεtiv εn positifu valyu dεm fכ -COHP kכrεspכnd to di antibonding stet εn binding stet, rispεktivli. Di bond trɛnk fɔ Co-O we HCOO adsɔb (Co-carbonyl O HCOO*) bin asɛs bay we dɛn intagret di -COHP valyu dɛn, we na bin 3.51 ɛn 3.38 fɔ Co-SAs/NPs@NC ɛn Co-SA, rispɛktvɔli. HCOOH adsכpshכn sho bak di sem kayn risכlt: di inkrεs pan di intagrεl valyu fכ -COHP afta nanopartikl dכping indikεt inkrεs pan Co-O bכndin, we de promuot di aktibכshכn fכ HCOO εn HCOOH ( Figure S45 ).
Latis strɔkchɔ fɔ Co-SA/NPs@NC-950. b PDOS Ko-SA/NP@NC-950 ɛn Kɔ SA. c 3D isosurface of di difrεns in chaj dεnsiti dεm fכ HCOOH adsכpshכn pan Co-SA/NPs@NC-950 εn Co-SA. (d) pCOHP fכ Co-O bכnd dεm we HCOO adsכp pan Co-SA/NPs@NC-950 (left) εn Co-SA (rayt). e Riakshɔn path fɔ HCOOH dihaydrojɛneshɔn pan Co-SA/NPs@NC-950 ɛn Co-SA.
Fכ bεtε כndastand di supεriכr dihaydrojenεshכn pεrformεns fכ Co-SA/NPs@NC, dεn bin establish di riakshכn pat εn εnεji. sכm spεshal wan, FA dihaydrojenεshכn involv fayv stεp dεm, inklud di kכnvכshכn fכ HCOOH to HCOOH*, HCOOH* to HCOO* + H*, HCOO* + H* to 2H* + CO2*, 2H* + CO2* to 2H* + CO2, εn 2H* insay H2 (Fig. 6e). di adsכpshכn enεji fכ fכmik asid mכlikul dεm na di katalis sεf tru kכbכksilik כksijεn de lכs pas tru haydroksil כksijεn (Figure S46 εn S47). afta dat, biכs fכ di lכw enεji, di adsכbεt de prεfrεns כnda OH bכnd klivεj fכ fכm HCOO* pas CH bכnd klivεj fכ fכm COOH*. di sem tεm, HCOO* de yuz monodentate adsכpshכn, we de protεkt di bכnd dεm we de brok εn di fכmeshכn fכ CO2 εn H2. dis rizulεt dεm kכnsist wit di prεsεns fכ wan νas(OCO) pik in in situ DRIFT, we de sho fכs se FA dεgradashכn de apin tru di fכmat path insay wi stכdi. I impɔtant fɔ no se akɔdin to KIE mɛzhɔmɛnt, CH disosieshɔn gɛt bɔku ay riakshɔn ɛnaji barɛri pas ɔda riakshɔn stɛp dɛn ɛn i de riprizent wan RDS. di enεji barεri fכ di optimal Co-SAs/NPs@NC katalis sistεm na 0.86 eV lכw pas di wan fכ Co-SA (1.2 eV), we de sכmtεm impruv di כvala dihaydrojenεshכn efyushכn. notis, di prεsεns fכ nanopartikl dεm de rεgεl di ilektronik strכkchכ fכ di atכmik dispersed kכaktiv sayt dεm, we de fכs εnhans di adsכpshכn εn aktibכshכn fכ intamεdiεt dεm, we de lכs di riakshכn barεri εn protεkt haydrojεn prodakshכn.
In sɔmari, wi de sho fɔ di fɔs tɛm se di katalaytik pefɔmɛns fɔ haydrojɛn prodakshɔn katalis dɛn kin rili impɔtant bay we wi de yuz matirial dɛn wit ayli distribyushɔn monomɛtal sɛnta ɛn smɔl nanopartikul dɛn. Dis kɔnsɛpt dɔn validet bay di sɛntesis fɔ kobalt-bɛs singl-atɔm mɛtal katalis dɛn we dɛn modify wit nanopartikl (Co-SAs/NPs@NC), ɛn bak rilayt matirial dɛn wit ɔl singl-mɛtal sɛnta (CoN2C2) ɔ Co NPs. Ɔl di matirial dɛn bin pripia bay wan simpul wan-step payrolaysis we. Structural analysis sho se di bes katalis (Co-SAs/NPs@NC-950) kכnsis fכ atomically dispersed CoN2C2 yunit dεm εn sכm nanopartikl dεm (7-8 nm) we dכp wit naytrojen εn grafayt-layk kabכn. I gɛt fayn fayn gas prodaktiviti we go rich 1403.8 ml g-1 h-1 (H2: CO2 = 1.01:1), H2 ɛn CO sɛlektiviti we na 99.96% ɛn i kin mentɛn kɔnstant aktiviti fɔ sɔm dez. di aktvכti fכ dis katalis pas di aktvכti fכ sכm Co SA εn Pd/C katalis dεm bay 4 εn 15 tεm, rispεktivli. in situ DRIFT εkspεriεns sho se we yu kכmpεr wit Co-SA, Co-SAs/NPs@NC-950 de sho strכng monodentate adsכpshכn fכ HCOO*, we imכtant fכ di fכmat path, εn dopant nanopartikl dεm kin promuot HCOO* aktibכshכn εn C–H aksεlεrayshכn . Di bond klivεj bin aydentify as RDS. Tiorikal kכlkyulshכn sho se Co NP dכping de inkrεs di d-band sεntr fכ singl Co atכm dεm bay 0.13 eV tru intarakshכn, εnhans di adsכpshכn fכ HCOOH* εn HCOO* intamεdiεt dεm, we de ridyus di riakshכn barεri frכm 1.20 eV fכ Co SA to 0 .86 eV. Na in gɛt di wok fɔ du fayn fayn wan.
Mɔ brayt wan, dis risach de gi aydia fɔ di dizayn fɔ nyu singl-atɔm mɛtal katalis ɛn advans ɔndastandin fɔ aw fɔ impɔtant katalis pefɔmɛns tru di sinajɛstik ifɛkt fɔ mɛtal sɛnta dɛn we gɛt difrɛn saiz. Wi biliv se dis aprɔch kin izi fɔ ɛkstɛnd to bɔku ɔda katalaytik sistɛm dɛn.
Co(NO3)2 6H2O (AR, 99%), Zn(NO3)2 6H2O (AR, 99%), 2-mɛtilimidazɔl (98%), mɛtanɔl (99.5%), prɔpilin kabɔnɛt (PC, 99% ) ɛtɛnol (AR, 99.7%) bin bay frɔm Maklin, Chaina. Fɔmik asid (HCOOH, 98%) bin bay frɔm Rhawn, Chaina. Ɔl di rijin dɛn bin yuz dairekt wan witout ɔda purifyeshɔn, ɛn dɛn bin pripia ɔltrapure wata yuz wan ultrapure purifyeshɔn sistem. Pt/C (5% mas lod) ɛn Pd/C (5% mas lod) bin bay frɔm Sigma-Aldrich.
Di sεntesis כf CoZn-ZIF nanokristals bin kכriכnt bays pan prεviכs mεtכd dεm wit sכm modifyushכn23,64. Fɔs, dɛn miks 30 mmol Zn(NO3)2·6H2O (8.925 g) ɛn 3.5 mmol Co(NO3)2·6H2O (1.014 g) ɛn sɔlv dɛn insay 300 ml mɛtanɔl. Afta dat, 120 mmol 2-methylimidazole (9.853 g) bin sכlv insay 100 ml mεtanכl εn ad am to di sכlushכn we de oba. Di miksɔp bin stɔp na rum tɛmpracha fɔ 24 awa. Fכ finish, di prodakt bin separet bay sεntrifugayshכn na 6429 g fכ 10 min εn was am gud gud wan wit mεtanכl tri tεm. Di pauda we kɔmɔt bin dray insay vaykum na 60°C ɔvnayt bifo dɛn yuz am.
Fכ sεntez Co-SAs/NPs@NC-950, dray CoZn-ZIF pauda bin pyrolyzed na 950 °C fכ 1 h insay wan gas fכ fכlכ 6% H2 + 94% Ar, wit wan hεtin rεt we na 5 °C/min. Afta dat, dɛn kol di sampul to rum tɛmpracha fɔ gɛt Co-SA/NPs@NC-950. Fɔ Co-SAs/NPs@NC-850 ɔ Co-SAs/NPs@NC-750, di payrolaysis tɛmpracha bin chenj to 850 ɛn 750 °C, rispɛktvɔli. Yu kin yuz sɛmpul dɛn we dɛn dɔn pripia we dɛn nɔ prosɛs dɛn mɔ, lɛk asid ɛch.
TEM (transmishɔn ilɛktron maykroskɔpi) mɛzhɔmɛnt dɛn bin du pan wan Thermo Fisher Titan Themis 60-300 “kub” maykroskɔp we gɛt wan aberreshɔn kɔrɛkshɔn fɔ imej ɛn wan 300 kV prob shep lens. HAADF-STEM ekspiriens dɛn bin du yuz FEI Titan G2 ɛn FEI Titan Themis Z maykroskɔp dɛn we gɛt prob ɛn imej kɔrɛkshɔn, ɛn bak DF4 4-sɛgmɛnt ditektɔ dɛn. EDS elemental mapping imej dɛn bin gɛt bak pan wan FEI Titan Themis Z maykroskɔp. XPS analisis bin de pan wan X-ray fotoelektrɔn spɛktromita (Thermo Fisher model ESCALAB 250Xi). XANES ɛn EXAFS spɛktra fɔ Co K-ɛj bin kɔlɛkt yuz wan XAFS-500 tebul (China Spectral Instruments Co., Ltd.). Co kɔntinyu bin de ditarmin bay atɔmik absɔpshɔn spɛktroskɔpi (AAS) (PinAAcle900T). X-ray difrakshɔn (XRD) spɛktra dɛn bin rɛkɛd pan wan X-ray difraktomita (Bruker, Bruker D8 Advance, Jamani). Naytrɔjen adsɔpshɔn isotɛm dɛn bin gɛt yuz wan fizik adsɔpshɔn aprɛshɔn (Micromeritics, ASAP2020, USA).
Di dihaydrojeneshɔn riakshɔn bin kɔmɔt na wan argon atmosfɛs wit ɛya we dɛn pul akɔdin to di standad Schlenk we. Di riakshɔn vessel bin ɛvakuet ɛn ful-ɔp am bak wit argon 6 tɛm. On di kondensa wata saplai ɛn ad katalis (30 mg) ɛn sɔlvɛnt (6 ml). Hɛt di kɔntena to di tɛmpracha we yu want yuz tɛmostayt ɛn alaw am fɔ ikwal fɔ 30 minit. Afta dat, dɛn ad fɔmik asid (10 mmol, 377 μL) to di riakshɔn vessel ɔnda argon. Tכn di tri-way bכret valv fכ dεprεshכn di riakta, kכloz am bak, εn bigin fכ mεzj di vכlyum כf gas we dεn prodyuz yuz manual bכret (Figure S16). Afta di tɛm we dɛn nid fɔ mek di riakshɔn dɔn, dɛn gɛda wan gas sɛmpul fɔ GC analisis we dɛn yuz wan gas-tayt sirinj we dɛn pul wit argon.
In situ drift ɛkspiriɛns dɛn bin du pan wan Fourier transfɔm infrarɛd (FTIR) spɛktromita (Thermo Fisher Scientific, Nicolet iS50) we gɛt wan mɛkkyuri kadmiɔm tɛlurayd (MCT) ditektɔ. Di katalis paoda bin put insay wan riakshɔn sɛl (Harrick Scientific Products, Praying Mantis). Afta we dɛn trit di katalis wit wan strim we gɛt Ar (50 ml/min) na rum tɛmpracha, dɛn ɔt di sampul to wan givɛn tɛmpracha, dɔn dɛn bɔbul am wit Ar (50 ml/min) insay wan HCOOH sɔlvushɔn ɛn tɔn am insay di in-situ riakshɔn sɛl. fɔ riakshɔn. Model hεtεrojεnik katalytik prכsεs dεm. Infrared spɛktra dɛn bin rɛkɛd pan intaval dɛn we de frɔm 3.0 sɛkɔn to 1 awa.
HCOOH, DCOOH, HCOOD ɛn DCOOD dɛn de yuz as sabstret insay prɔpilin kabɔnɛt. di rεmεnεnt kכndishכn dεm kכrεkt to di HCOOH dεhaydrojenεshכn prosidכs.
Fɔs prinsipul kɔlkyulɛshɔn dɛn bin du yuz di density fɛnshɔnal tiori fremwɔk insay di Vienna Ab initio mɔdelin pakej (VASP 5.4.4) 65,66. A superunit sel wit grafin surface (5 × 5) wit transvas dimɛnshɔn we na lɛk 12.5 Å bin yuz as sabstret fɔ CoN2C2 ɛn CoN2C2-Co6. A vaykum distans we pas 15 Å bin ad fɔ avɔyd intarakshɔn bitwin adjasent sabstret layers. di intarakshכn bitwin ayכn εn εlektrכn dεn dεskrεb am bay di projεkt amplifyed wεv (PAW) mεtכd65,67. Di Perdue-Burke-Ernzerhoff (PBE) jenɛralized gradient aprɔksimɛshɔn (GGA) fɛnshɔn we Grimm bin prɔpɔz wit van der Waals kɔrɛkshɔn68,69 bin yuz. Di kכnvεgεshכn krayteria fכ tכtal εnεji εn fכs na 10−6 eV/atכm εn 0.01 eV/Å. Di enaji kot-of bin set na 600 eV yuz wan Monkhorst-Pack 2 × 2 × 1 K-point grid. Di pseudopotensial we dɛn yuz na dis mɔdel na in dɛn kɔnstrɔk frɔm di ilɛktronik kɔnfigyushɔn insay di C 2s22p2 stet, N 2s22p3 stet, Co 3d74s2 stet, H 1 s1 stet, ɛn O 2s22p4 stet. di adsכpshכn enεji εn εlektrכn dεnsiti difrεns dεn kכl am bay we dεn pul di enεji fכ di gas fεz εn sכfayz spεshal frכm di enεji fכ di adsכpshכn sistεm akɔdin to adsכpshכn כ intafεys mכdel70,71,72,73,74. Di Gibs fri enaji kɔrɛkshɔn de yuz fɔ kɔnvɔyt DFT ɛnaji to Gibs fri ɛnaji ɛn tek kɔnt ɔf vaybreshɔn kɔntribyushɔn to ɛntrɔpi ɛn ziro pɔynt ɛnaji75. Di ascending imej-nudging elastik band (CI-NEB) mεtכd bin yuz fכ sכch fכ di transishכn stet fכ di riakshכn76.
Ɔl di data we dɛn gɛt ɛn analayz we dɛn de du dis stɔdi, de insay di atikul ɛn sɔpɔtmɛnt matirial dɛn ɔ dɛn kin gɛt am frɔm di kɔrɛspɔndɛns ɔda pɔsin we rayt am if i aks fɔ am fayn fayn wan. Dɛn gi di sɔs data fɔ dis atikul.
Ɔl di kɔd dɛn we dɛn yuz na di simulshɔn dɛn we de wit dis atikul de frɔm di kɔrɛspɔndɛns ɔda pipul dɛn we dɛn aks fɔ am.
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