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Kukula kwa ukadaulo wa haidrojeni kuli pakati pa chuma chobiriwira. Monga chofunikira pakusunga haidrojeni, ma catalyst ogwira ntchito komanso okhazikika a hydrogenation (de)hydrogenation reaction amafunika. Mpaka pano, dera lino lakhala likulamulidwa ndi kugwiritsa ntchito zitsulo zamtengo wapatali zodula. Pano, tikupereka njira yatsopano yotsika mtengo yochokera ku cobalt (Co-SAs/NPs@NC) momwe malo ogawidwa kwambiri achitsulo chimodzi amagwirizanitsidwa mogwirizana ndi tinthu tating'onoting'ono tating'onoting'ono kuti akwaniritse bwino kuchotsedwa kwa asidi. Pogwiritsa ntchito zinthu zabwino kwambiri za mayunitsi a CoN2C2 omwazikana ndi ma nanoparticles okhala ndi kukula kwa 7-8 nm, pogwiritsa ntchito propylene carbonate ngati solvent, kupanga mpweya wabwino kwambiri wa 1403.8 ml g-1 h-1 kunapezeka, ndipo panalibe kutayika pambuyo pa ntchito ya 5 cycles, yomwe ndi yabwino nthawi 15 kuposa Pd/C yogulitsa. Mayeso a malo omwe alipo akuwonetsa kuti, poyerekeza ndi ma atomu achitsulo chimodzi ndi ma catalyst a nanoparticle okhudzana nawo, Co-SAs/NPs@NC imakulitsa kulowetsedwa ndi kuyatsidwa kwa key monodentate intermediate HCOO*, motero kumalimbikitsa kugawanika kwa CH bond. Mawerengedwe a chiphunzitso akuwonetsa kuti kuphatikiza kwa cobalt nanoparticles kumathandizira kusintha kwa d-band center ya atomu imodzi ya Co kukhala malo ogwirira ntchito, motero kumawonjezera kulumikizana pakati pa carbonyl O ya HCOO* intermediate ndi Co center, potero kumachepetsa chotchinga cha mphamvu.
Hydrojeni imaonedwa kuti ndi yonyamula mphamvu yofunika kwambiri pakusintha kwa mphamvu padziko lonse lapansi ndipo ikhoza kukhala chinthu chofunikira kwambiri pakukwaniritsa kusalowerera kwa kaboni1. Chifukwa cha makhalidwe ake monga kuyaka komanso kutsika kwa kachulukidwe, kusungirako bwino komanso kunyamula kwa hydrogen ndi nkhani zazikulu pakukwaniritsa chuma cha hydrogen2,3,4. Zonyamula hydrogen zamadzimadzi (LOHCs), zomwe zimasunga ndikutulutsa hydrogen kudzera muzochita zamakemikolo, zaperekedwa ngati yankho. Poyerekeza ndi hydrogen ya mamolekyulu, zinthu zotere (methanol, toluene, dibenzyltoluene, ndi zina zotero) ndizosavuta komanso zosavuta kuzigwira5,6,7. Pakati pa ma LOHC osiyanasiyana achikhalidwe, formic acid (FA) ili ndi poizoni wochepa (LD50: 1.8 g/kg) ndi mphamvu ya H2 ya 53 g/L kapena 4.4 wt%. Chodziwika bwino ndichakuti, FA ndiye LOHC yokhayo yomwe ingasunge ndikutulutsa hydrogen pansi pamikhalidwe yofatsa pamaso pa ma catalysts oyenera, motero sikufuna mphamvu zambiri zakunja1,8,9. Ndipotu, ma catalyst ambiri achitsulo chodziwika bwino apangidwa kuti achepetse ma formic acid, mwachitsanzo, ma catalyst ochokera ku palladium ndi ogwira ntchito nthawi 50-200 kuposa ma catalyst achitsulo otsika mtengo10,11,12. Komabe, ngati muganizira mtengo wa zitsulo zogwira ntchito, mwachitsanzo, palladium ndi yokwera mtengo nthawi zoposa 1000.
Cobalt, Kufunafuna zinthu zoyambira zachitsulo zogwira ntchito kwambiri komanso zokhazikika zikupitilira kukopa chidwi cha ofufuza ambiri m'maphunziro ndi mafakitale13,14,15.
Ngakhale kuti ma catalyst otsika mtengo ochokera ku Mo ndi Co, komanso ma nanocatalyst opangidwa kuchokera ku noble/base metal alloys, 14,16 apangidwa kuti achepetse FA, kuchepetsa kwawo pang'onopang'ono panthawi ya reaction sikungapeweke chifukwa cha kukhala kwa malo ogwirira ntchito a zitsulo, CO2, ndi H2O ndi ma proton kapena ma anion (HCOO-), kuipitsidwa kwa FA, kusonkhana kwa tinthu tating'onoting'ono ndi poyizoni wa CO17,18. Ife ndi ena posachedwapa tawonetsa kuti ma catalyst a atomu imodzi (SACs) okhala ndi malo ofalikira kwambiri a CoIINx ngati malo ogwirira ntchito amathandizira reactivity ndi kukana kwa asidi ya formic acid dehydrogenation poyerekeza ndi nanoparticles17,19,20,21,22,23,24. Mu zinthu izi za Co-NC, ma atomu a N amagwira ntchito ngati malo akuluakulu olimbikitsira FA deprotonation pomwe akuwonjezera kukhazikika kwa kapangidwe kake kudzera mu mgwirizano ndi atomu yapakati ya Co2, pomwe ma atomu a Co amapereka malo okhudzidwa ndi H ndikulimbikitsa CH22 scission, 25,26. Mwatsoka, ntchito ndi kukhazikika kwa ma catalyst awa akadali kutali ndi ma catalyst amakono achitsulo chofanana komanso chosiyana (Chithunzi 1) 13.
Mphamvu yochulukirapo kuchokera kuzinthu zongowonjezedwanso monga dzuwa kapena mphepo imatha kupangidwa ndi electrolysis ya madzi. Hydrogen yomwe imapangidwa imatha kusungidwa pogwiritsa ntchito LOHC, madzi omwe hydrogenation ndi dehydrogenation yake zimatha kubwezeretsedwanso. Mu gawo la dehydrogenation, chinthu chokhacho ndi hydrogen, ndipo madzi onyamula amabwezeretsedwa momwe analili poyamba ndikuwonjezeredwa hydrogen. Hydrogen pamapeto pake ingagwiritsidwe ntchito m'malo opangira mafuta, mabatire, nyumba zamafakitale, ndi zina zambiri.
Posachedwapa, zanenedwa kuti ntchito yeniyeni ya ma SAC enaake ikhoza kukulitsidwa pamaso pa ma atomu osiyanasiyana achitsulo kapena malo ena achitsulo operekedwa ndi nanoparticles (NPs) kapena nanoclusters (NCs)27,28. Izi zimatsegula mwayi wowonjezera kulowetsedwa ndi kuyatsidwa kwa substrate, komanso kusintha kwa geometry ndi kapangidwe ka zamagetsi ka malo a monatomic. Mwanjira imeneyi, kulowetsedwa/kuyatsidwa kwa substrate kumatha kukonzedwanso, kupereka mphamvu yabwino kwambiri yolumikizira29,30. Izi zimatipatsa lingaliro lopanga zinthu zoyenera zolumikizira ndi malo ogwirira ntchito osakanizidwa. Ngakhale ma SAC okonzedwa bwino awonetsa kuthekera kwakukulu mu ntchito zosiyanasiyana zolumikizira31,32,33,34,35,36, monga momwe tikudziwira, ntchito yawo pakusungira haidrojeni siikudziwika bwino. Pachifukwa ichi, tikupereka njira yosinthasintha komanso yolimba yopangira ma catalyst osakanikirana ndi cobalt (Co-SAs/NPs@NCs) omwe ali ndi ma nanoparticles odziwika bwino ndi malo achitsulo payokha. Co-SAs/NPs@NC yokonzedwa bwino ikuwonetsa magwiridwe antchito abwino kwambiri a formic acid dehydrogenation, zomwe zili bwino kuposa ma catalyst osapangidwa bwino (monga CoNx, ma atomu a cobalt amodzi, cobalt@NC ndi γ-Mo2N) komanso ma catalyst achitsulo abwino. Kufotokozera momwe zinthu zilili komanso kuwerengera kwa DFT kwa ma catalyst ogwira ntchito kumasonyeza kuti malo achitsulo amodzi ndi amodzi amagwira ntchito ngati malo ogwirira ntchito, ndipo tinthu tating'onoting'ono ta chipangizochi timawonjezera pakati pa ma atomu a Co, kumalimbikitsa kuyamwa ndi kuyambitsa HCOO*, potero kumachepetsa chotchinga cha mphamvu cha reaction.
Mafelemu a Zeolite imidazolate (ZIFs) ndi ma precursors odziwika bwino omwe amapereka ma catalysts a zinthu za kaboni zopangidwa ndi nayitrogeni (ma catalysts a metal-NC) kuti athandizire mitundu yosiyanasiyana ya zitsulo37,38. Chifukwa chake, Co(NO3)2 ndi Zn(NO3)2 zimasakanikirana ndi 2-methylimidazole mu methanol kuti apange ma complexes achitsulo ofanana mu yankho. Pambuyo pa centrifugation ndi kuumitsa, CoZn-ZIF idasinthidwa kutentha kosiyanasiyana (750–950 °C) mumlengalenga wa 6% H2 ndi 94% Ar. Monga momwe zasonyezedwera pachithunzi pansipa, zinthu zomwe zimachokera zimakhala ndi mawonekedwe osiyanasiyana a malo ogwirira ntchito ndipo zimatchedwa Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750 (Chithunzi 2a). ). Kuwona kwapadera kwa njira zina zofunika pakupangira kwafotokozedwa mwatsatanetsatane mu Zithunzi 1 ndi 2. C1-C3. Kusinthasintha kwa kutentha kwa X-ray (VTXRD) kunachitika kuti kuwone kusintha kwa catalyst. Kutentha kwa pyrolysis kukafika pa 650 °C, mawonekedwe a XRD amasintha kwambiri chifukwa cha kugwa kwa kapangidwe ka kristalo ka ZIF (Chithunzi S4) 39. Pamene kutentha kukuchulukirachulukira, nsonga ziwiri zazikulu zimawonekera mu mawonekedwe a XRD a Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750 pa 20–30° ndi 40–50°, zomwe zikuyimira nsonga ya kaboni yopanda mawonekedwe (Chithunzi C5). 40. Ndikofunikira kudziwa kuti nsonga zitatu zokha zomwe zimawonedwa ndi 44.2°, 51.5° ndi 75.8°, zomwe ndi za cobalt yachitsulo (JCPDS #15-0806), ndi 26.2°, zomwe ndi za graphitic carbon (JCPDS # 41-1487). Sipekitiramu ya X-ray ya Co-SAs/NPs@NC-950 ikuwonetsa kukhalapo kwa tinthu tating'onoting'ono ta cobalt tofanana ndi graphite pa catalyst41,42,43,44. Sipekitiramu ya Raman ikuwonetsa kuti Co-SAs/NPs@NC-950 ikuwoneka kuti ili ndi ma D ndi G peaks amphamvu komanso opapatiza kuposa zitsanzo zina, zomwe zikusonyeza kuti graphitization ndi yapamwamba kwambiri (Chithunzi S6). Kuphatikiza apo, Co-SAs/NPs@NC-950 ikuwonetsa Brunner-Emmett-Taylor (BET) pamwamba ndi voliyumu ya pore (1261 m2 g-1 ndi 0.37 cm3 g-1) kuposa zitsanzo zina ndipo ma ZIF ambiri ndi zinthu zochokera ku NC (Chithunzi S7 ndi Table S1). Atomic absorption spectroscopy (AAS) ikuwonetsa kuti kuchuluka kwa cobalt mu Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@ ndi 2.69 wt.%, 2.74 wt.% ndi 2.73 wt.%. NC-750 motsatana (Table S2). Kuchuluka kwa Zn mu Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750 kumawonjezeka pang'onopang'ono, zomwe zimachitika chifukwa cha kuchepa kwakukulu ndi kusinthasintha kwa mayunitsi a Zn. Kuwonjezeka kwa kutentha kwa pyrolysis (Zn, boiling point = 907 °C) 45.46. Elemental analysis (EA) inawonetsa kuti kuchuluka kwa N kumachepa ndi kutentha kwa pyrolysis komwe kumawonjezeka, ndipo kuchuluka kwa O2 kungakhale chifukwa cha kuyamwa kwa molekyulu O2 kuchokera ku mpweya. (Table S3). Pa kuchuluka kwa cobalt, tinthu tating'onoting'ono ndi ma coatom olekanitsidwa amakhala pamodzi, zomwe zimapangitsa kuti ntchito ya catalyst ichuluke kwambiri, monga tafotokozera pansipa.
Chithunzi cha kapangidwe ka Co-SA/NPs@NC-T, komwe T ndi kutentha kwa pyrolysis (°C). b chithunzi cha TEM. c Chithunzi cha Co-SAs/NPs@NC-950 AC-HAADF-STEM. Maatomu a Co imodzi amalembedwa ndi mabwalo ofiira. d EDS spectrum ya Co-SA/NPs@NC-950.
Chochititsa chidwi n'chakuti, ma microscopy a ma electron otumizira (TEM) adawonetsa kupezeka kwa ma cobalt nanoparticles (NPs) osiyanasiyana okhala ndi kukula kwapakati pa 7.5 ± 1.7 nm kokha mu Co-SAs/NPs@NC-950 (Zithunzi 2 b ndi S8). Ma nanoparticles awa ali ndi graphite-like carbon doped ndi nayitrogeni. Malo ozungulira a lattice fringe a 0.361 ndi 0.201 nm akugwirizana ndi graphite carbon (002) ndi metallic Co (111) particles, motsatana. Kuphatikiza apo, high-angle aberration-corrected annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) adawonetsa kuti ma Co NPs mu Co-SAs/NPs@NC-950 anali ozunguliridwa ndi atomic cobalt wochuluka (Chithunzi 2c). Komabe, ma atomu a cobalt omwazikana ndi atomic okha ndi omwe adawonedwa pothandizidwa ndi zitsanzo zina ziwiri (Chithunzi S9). Chithunzi cha HAADF-STEM cha Energy dispersive spectroscopy (EDS) chikuwonetsa kufalikira kofanana kwa C, N, Co ndi Co NPs zolekanitsidwa mu Co-SAs/NPs@NC-950 (Chithunzi 2d). Zotsatira zonsezi zikuwonetsa kuti malo osakanikirana a Co ndi nanoparticles omwe ali mu carbon ya N-doped graphite-like carbon amamangiriridwa bwino ku ma substrates a NC mu Co-SAs/NPs@NC-950, pomwe malo opangidwa ndi zitsulo okha ndi omwe ali okha.
Mkhalidwe wa valence ndi kapangidwe ka mankhwala a zinthu zomwe zapezeka zidaphunziridwa ndi X-ray photoelectron spectroscopy (XPS). XPS spectra ya ma catalyst atatuwa idawonetsa kupezeka kwa zinthu Co, N, C ndi O, koma Zn inalipo mu Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750 (Chithunzi 2). ). C10). Pamene kutentha kwa pyrolysis kukukwera, kuchuluka kwa nayitrogeni kumachepa pamene mitundu ya nayitrogeni imakhala yosakhazikika ndikuwola kukhala mpweya wa NH3 ndi NOx pa kutentha kwakukulu (Table S4) 47. Chifukwa chake, kuchuluka kwa kaboni konse kudakwera pang'onopang'ono kuchokera ku Co-SAs/NPs@NC-750 kupita ku Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-950 (Zithunzi S11 ndi S12). Chitsanzo chotenthetsera kutentha kwakukulu chili ndi gawo lochepa la maatomu a nayitrogeni, zomwe zikutanthauza kuti kuchuluka kwa ma NC carriers mu Co-SAs/NPs@NC-950 kuyenera kukhala kochepa kuposa komwe kuli m'zitsanzo zina. Izi zimapangitsa kuti tinthu ta cobalt tiwonongeke kwambiri. Sipekitiramu ya O1s imasonyeza nsonga ziwiri C=O (531.6 eV) ndi C–O (533.5 eV), motsatana (Chithunzi S13) 48. Monga momwe zasonyezedwera pa Chithunzi 2a, sipekitiramu ya N1s ikhoza kuthetsedwa kukhala nsonga zinayi za pyridine nitrogen N (398.4 eV), pyrrole N (401.1 eV), graphite N (402.3 eV) ndi Co-N (399.2 eV). Ma Co-N bonds alipo m'zitsanzo zonse zitatu, zomwe zikusonyeza kuti maatomu ena a N amagwirizanitsidwa ndi malo a monometallic, koma makhalidwe amasiyana kwambiri49. Kugwiritsa ntchito kutentha kwakukulu kwa pyrolysis kungachepetse kwambiri kuchuluka kwa mitundu ya Co-N kuchokera pa 43.7% mu Co-SA/NPs@NC-750 mpaka 27.0% mu Co-SAs/NPs@NC-850 ndi Co 17.6%@ NC-950. mu -CA/NPs, zomwe zikugwirizana ndi kuwonjezeka kwa kuchuluka kwa C (Chithunzi 3a), zomwe zikusonyeza kuti nambala yawo yolumikizirana ya Co-N ikhoza kusintha ndikusinthidwa pang'ono ndi maatomu a C50. Zn 2p spectrum ikuwonetsa kuti chinthuchi chilipo makamaka mu mawonekedwe a Zn2+. (Chithunzi S14) 51. Sipekitiramu ya Co2p ikuwonetsa nsonga ziwiri zodziwika bwino pa 780.8 ndi 796.1 eV, zomwe zimayambitsidwa ndi Co 2p3/2 ndi Co 2p1/2, motsatana (Chithunzi 3b). Poyerekeza ndi Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750, nsonga ya Co-N mu Co-SAs/NPs@NC-950 imasunthidwa kumbali yabwino, zomwe zikusonyeza kuti atomu imodzi ya Co pamwamba pa -SAs/NPs@NC-950 ili ndi digiri yapamwamba ya kuchepa kwa ma elekitironi, zomwe zimapangitsa kuti pakhale mkhalidwe wochuluka wa okosijeni. Ndikofunikira kudziwa kuti Co-SAs/NPs@NC-950 yokha ndi yomwe inawonetsa chiwopsezo chofooka cha zero-valent cobalt (Co0) pa 778.5 eV, zomwe zimatsimikizira kukhalapo kwa nanoparticles zomwe zimachitika chifukwa cha kusonkhana kwa SA cobalt pa kutentha kwakukulu.
a N 1s ndi b Co 2p spectra ya Co-SA/NPs@NC-T. c XANES ndi d FT-EXAFS spectra ya Co-K-edge ya Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750. e WT-EXAFS contour plots ya Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850, ndi Co-SAs/NPs@NC-750. f FT-EXAFS fitting curve ya Co-SA/NPs@NC-950.
Kenako, X-ray absorption spectroscopy (XAS) yotsekedwa nthawi inagwiritsidwa ntchito pofufuza kapangidwe ka zamagetsi ndi malo ogwirizanitsa a mitundu ya Co mu chitsanzo chokonzedwa. Ma Cobalt valence states mu Co-SAs/NPs@NC-950, Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750 Kapangidwe ka m'mphepete kamawululidwa ndi kuyamwa kwa X-ray komwe kumakhala kofanana ndi munda pa Co-K edge (XANES) spectrum. Monga momwe zasonyezedwera pa Chithunzi 3c, kuyamwa pafupi ndi m'mphepete mwa zitsanzo zitatu kuli pakati pa Co ndi CoO foils, zomwe zikusonyeza kuti mkhalidwe wa valence wa mitundu ya Co uli pakati pa 0 mpaka +253. Kuphatikiza apo, kusintha kupita ku mphamvu yotsika kunawonedwa kuchokera ku Co-SAs/NPs@NC-950 kupita ku Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750, zomwe zikusonyeza kuti Co-SAs/NPs@NC-750 ili ndi mkhalidwe wotsika wa okosijeni. Dongosolo losinthira. Malinga ndi zotsatira za kuyika kophatikizana kolunjika, mkhalidwe wa Co valence wa Co-SAs/NPs@NC-950 ukuyembekezeka kukhala +0.642, womwe ndi wocheperako kuposa mkhalidwe wa Co valence wa Co-SAs/NPs@NC-850 (+1.376). Co-SA/NP @NC-750 (+1.402). Zotsatirazi zikusonyeza kuti mkhalidwe wapakati wa okosijeni wa tinthu ta cobalt mu Co-SAs/NPs@NC-950 wachepa kwambiri, zomwe zikugwirizana ndi zotsatira za XRD ndi HADF-STEM ndipo zitha kufotokozedwa ndi kukhalapo kwa cobalt nanoparticles ndi single cobalt. Maatomu a Co 41. Fourier transform X-ray absorption fine structure (FT-EXAFS) spectrum ya Co K-edge ikuwonetsa kuti nsonga yayikulu pa 1.32 Å ndi ya chipolopolo cha Co-N/Co-C, pomwe njira yofalikira ya Co-Co yachitsulo ili pa 2.18 yokha mu Co-SAs Å yomwe imapezeka mu /NPs@NC-950 (Chithunzi 3d). Kuphatikiza apo, mawonekedwe a contour ya wavelet transform (WT) akuwonetsa mphamvu yayikulu pa 6.7 Å-1 yolumikizidwa ndi Co-N/Co-C, pomwe Co-SAs/NPs@NC-950 yokha ndi yomwe ikuwonetsa mphamvu yayikulu yolumikizidwa ndi 8.8. Mphamvu yayikulu ina ili pa Å−1 ku Co-Co bond (Chithunzi 3e). Kuphatikiza apo, kusanthula kwa EXAFS komwe wobwereketsa adachita kunawonetsa kuti kutentha kwa pyrolysis kwa 750, 850 ndi 950 °C, manambala ogwirizana a Co-N anali 3.8, 3.2 ndi 2.3, motsatana, ndipo manambala ogwirizana a Co-C anali 0. 0.9 ndi 1.8 (Chithunzi 3f, S15 ndi Table S1). Mwachindunji, zotsatira zaposachedwa zitha kufotokozedwa ndi kukhalapo kwa mayunitsi a CoN2C2 omwazikana ndi ma nanoparticles mu Co-SAs/NPs@NC-950. Mosiyana ndi zimenezi, mu Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750, mayunitsi a CoN3C ndi CoN4 okha ndi omwe alipo. N'zoonekeratu kuti kutentha kwa pyrolysis kukukwera, maatomu a N mu unit ya CoN4 amasinthidwa pang'onopang'ono ndi maatomu a C, ndipo cobalt CA imasonkhana kuti ipange ma nanoparticles.
Mikhalidwe yochitidwa kale idagwiritsidwa ntchito pophunzira momwe mikhalidwe yokonzekera imakhudzira makhalidwe a zinthu zosiyanasiyana (Chithunzi S16)17,49. Monga momwe zasonyezedwera pa Chithunzi 4 a, ntchito ya Co-SAs/NPs@NC-950 ndi yayikulu kwambiri kuposa ya Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750. Chodziwika bwino n'chakuti, zitsanzo zonse zitatu za Co zokonzedwa zidawonetsa magwiridwe antchito apamwamba poyerekeza ndi ma catalysts achitsulo chamtengo wapatali (Pd/C ndi Pt/C). Kuphatikiza apo, zitsanzo za Zn-ZIF-8 ndi Zn-NC sizinagwire ntchito polimbana ndi kuchepa kwa hydrogenation ya formic acid, zomwe zikusonyeza kuti tinthu ta Zn si malo ogwirira ntchito, koma zotsatira zake pa ntchitoyo sizochepa. Kuphatikiza apo, ntchito ya Co-SAs/NPs@NC-850 ndi Co-SAs/NPs@NC-750 idachitika pyrolysis yachiwiri pa 950°C kwa ola limodzi, koma inali yotsika kuposa ya Co-SAs/NPs@NC-750. @NC-950 (Chithunzi S17). Kapangidwe ka zinthuzi kunawonetsa kukhalapo kwa ma nanoparticles a Co mu zitsanzo zomwe zinapangidwanso, koma malo otsika komanso kusowa kwa kaboni wofanana ndi graphite kunapangitsa kuti ntchito ikhale yochepa poyerekeza ndi Co-SAs/NPs@NC-950 (Chithunzi S18–S20). Ntchito ya zitsanzo zomwe zili ndi kuchuluka kosiyana kwa Co precursor inayerekezeredwanso, ndipo ntchito yayikulu kwambiri yawonetsedwa pa 3.5 mol yowonjezera (Table S6 ndi Chithunzi S21). N'zoonekeratu kuti kupangika kwa malo osiyanasiyana achitsulo kumakhudzidwa ndi kuchuluka kwa haidrojeni mumlengalenga wa pyrolysis ndi nthawi ya pyrolysis. Chifukwa chake, zinthu zina za Co-SAs/NPs@NC-950 zinayesedwa kuti ziwone ngati pali formic acid dehydrogenation activity. Zinthu zonse zinawonetsa magwiridwe antchito abwino kwambiri; komabe, palibe chomwe chinali chabwino kuposa Co-SAs/NPs@NC-950 (Zithunzi S22 ndi S23). Kapangidwe ka zinthuzo kakusonyeza kuti nthawi ya pyrolysis ikuwonjezeka, kuchuluka kwa malo a monoatomic Co-N kumachepa pang'onopang'ono chifukwa cha kusonkhana kwa maatomu achitsulo kukhala tinthu tating'onoting'ono, zomwe zimafotokoza kusiyana kwa ntchito pakati pa zitsanzo ndi nthawi ya pyrolysis ya 100-2000. kusiyana kwa 0.5 h, 1 h, ndi 2 h (Zithunzi S24–S28 ndi Table S7).
Chithunzi cha kuchuluka kwa mpweya poyerekeza ndi nthawi yomwe yapezeka panthawi yochotsa madzi m'mafakitale amafuta pogwiritsa ntchito ma catalyst osiyanasiyana. Mikhalidwe ya reaction: PC (10 mmol, 377 μl), catalyst (30 mg), PC (6 ml), Tback: 110 °C, Tactical: 98 °C, magawo 4 b Co-SAs/NPs@NC-950 (30 mg), ma solvent osiyanasiyana. c Kuyerekeza kwa kuchuluka kwa kusintha kwa mpweya kwa ma catalyst osiyanasiyana mu ma solvents achilengedwe pa 85–110 °C. d Co-SA/NPs@NC-950 recycling experiment. Mikhalidwe ya reaction: FA (10 mmol, 377 µl), Co-SAs/NPs@NC-950 (30 mg), solvent (6 ml), Tset: 110 °C, Tactual: 98 °C, reaction cycle iliyonse imatenga ola limodzi. Mipiringidzo yolakwika ikuyimira kupotoka kokhazikika komwe kumawerengedwa kuchokera ku mayeso atatu ogwira ntchito.
Kawirikawiri, kugwira ntchito bwino kwa ma catalyst a FA dehydrogenation kumadalira kwambiri momwe zinthu zimachitikira, makamaka solvent yomwe imagwiritsidwa ntchito8,49. Pogwiritsa ntchito madzi ngati solvent, Co-SAs/NPs@NC-950 inawonetsa kuchuluka kwa reaction koyambirira, koma deactivation inachitika, mwina chifukwa cha ma proton kapena H2O18 omwe amakhala m'malo omwe amagwira ntchito. Kuyesedwa kwa catalyst mu organic solvents monga 1,4-dioxane (DXA), n-butyl acetate (BAC), toluene (PhMe), triglyme ndi cyclohexanone (CYC) sikunawonetse kusintha kulikonse, komanso mu propylene carbonate (PC)) (Chithunzi 4b ndi Table S8). Momwemonso, zowonjezera monga triethylamine (NEt3) kapena sodium formate (HCCONA) sizinathandizenso pa ntchito ya catalyst (Chithunzi S29). Pansi pa mikhalidwe yabwino kwambiri yochitira zinthu, mpweya unafika pa 1403.8 mL g−1 h−1 (Chithunzi S30), chomwe chinali chokwera kwambiri kuposa ma catalyst onse a Co omwe adanenedwa kale (kuphatikiza SAC17, 23, 24). Mu zoyeserera zosiyanasiyana, kupatula ma reaction m'madzi ndi zowonjezera za formate, dehydrogenation ndi dehydration selectivities mpaka 99.96% zidapezeka (Table S9). Mphamvu yoyeserera yowerengedwa ndi 88.4 kJ/mol, yomwe ikufanana ndi mphamvu yoyambitsa ya ma catalyst achitsulo chabwino (Chithunzi S31 ndi Table S10).
Kuphatikiza apo, tinayerekeza ma catalyst ena osiyanasiyana kuti athetseretu acid m'mikhalidwe yofanana (Chithunzi 4c, matebulo S11 ndi S12). Monga momwe zasonyezedwera pa Chithunzi 3c, kuchuluka kwa mpweya wopangidwa ndi Co-SAs/NPs@NC-950 kumaposa kuchuluka kwa ma catalyst achitsulo odziwika bwino ndipo ndi okwera nthawi 15 ndi 15 kuposa a 5% Pd/C ndi 5% Pd/C, motsatana, ndi 10 kamodzi. % Pt/C catalyst.
Mbali yofunika kwambiri ya kugwiritsa ntchito (de)hydrogenation catalysts ndi kukhazikika kwawo. Chifukwa chake, mayeso angapo obwezeretsanso pogwiritsa ntchito Co-SAs/NPs@NC-950 adachitika. Monga momwe zasonyezedwera pa Chithunzi 4 d, ntchito yoyambirira ndi kusankha kwa zinthuzo sizinasinthe pa maulendo asanu otsatizana (onaninso Table S13). Mayeso a nthawi yayitali adachitika ndipo kupanga mpweya kunawonjezeka molunjika kwa maola 72 (Chithunzi S32). Kuchuluka kwa cobalt mu Co-SA/NPs@NC-950 yogwiritsidwa ntchito kunali 2.5 wt%, komwe kunali pafupi kwambiri ndi kwa catalyst watsopano, zomwe zikusonyeza kuti panalibe leaching yodziwikiratu ya cobalt (Table S14). Palibe kusintha koonekeratu kwa mitundu kapena kusonkhana kwa tinthu tachitsulo komwe kunawonedwa isanachitike komanso pambuyo pa zomwe zinachitika (Chithunzi S33). AC-HAADF-STEM ndi EDS ya zinthu zomwe zinagwiritsidwa ntchito poyesa kwa nthawi yayitali zidawonetsa kusungidwa ndi kufalikira kofanana kwa malo ofalikira a atomu ndipo palibe kusintha kwakukulu kwa kapangidwe kake (Zithunzi S34 ndi S35). Ma peaks odziwika bwino a Co0 ndi Co-N akadalipo mu XPS, zomwe zimatsimikizira kukhalapo kwa Co NPs ndi malo achitsulo payokha, zomwe zimatsimikiziranso kukhazikika kwa Co-SAs/NPs@NC-950 catalyst (Chithunzi S36).
Kuti tidziwe malo omwe amagwira ntchito kwambiri omwe amachititsa kuti asidi asungunuke, zinthu zosankhidwa zokhala ndi pakati pachitsulo chimodzi (CoN2C2) kapena Co NP zinakonzedwa kutengera maphunziro am'mbuyomu17. Dongosolo la ntchito ya formic acid dehydrogenation yomwe idawonedwa pansi pa mikhalidwe yomweyi ndi Co-SAs/NPs@NC-950 > Co SA > Co NP (Table S15), zomwe zikusonyeza kuti malo a CoN2C2 omwazikana ndi atomiki ndi otanganidwa kwambiri kuposa NPs. Kinetics ya reaction ikuwonetsa kuti kusintha kwa haidrojeni kumatsatira kinetics ya reaction yoyamba, koma malo otsetsereka angapo okhala ndi cobalt osiyanasiyana si ofanana, zomwe zikusonyeza kuti kinetics sizimadalira pa formic acid yokha, komanso pamalo omwe akugwira ntchito (Chithunzi 2). C37). Kafukufuku wina wa kinetic adawonetsa kuti, popeza palibe cobalt metal peaks mu X-ray diffraction analysis, kinetic order ya reaction malinga ndi kuchuluka kwa cobalt idapezeka kuti ndi 1.02 pamlingo wotsika (osakwana 2.5%), zomwe zikusonyeza kufalikira kofanana kwa malo a monoatomic cobalt. main. malo ogwirira ntchito (zithunzi S38 ndi S39). Pamene kuchuluka kwa tinthu ta Co kufika pa 2.7%, r imawonjezeka mwadzidzidzi, zomwe zikusonyeza kuti tinthu tating'onoting'ono timagwirizana bwino ndi ma atomu kuti tipeze ntchito yayikulu. Pamene kuchuluka kwa tinthu ta Co kukuwonjezeka, kupindika kumakhala kosagwirizana, komwe kumalumikizidwa ndi kuwonjezeka kwa kuchuluka kwa tinthu tating'onoting'ono komanso kuchepa kwa malo a monatomic. Chifukwa chake, magwiridwe antchito abwino a LC dehydrogenation a Co-SA/NPs@NC-950 amachokera ku machitidwe ogwirizana a malo achitsulo ndi tinthu tating'onoting'ono.
Kafukufuku wozama adachitika pogwiritsa ntchito in situ diffuse reflectance Fourier transform (in situ DRIFT) kuti adziwe zinthu zomwe zimayambitsa kusintha kwa kutentha. Pambuyo potenthetsa zitsanzozo ku kutentha kosiyanasiyana kwa kutentha pambuyo powonjezera formic acid, ma frequency awiri adawonedwa (Chithunzi 5a). Nsonga zitatu za HCOOH* zimawonekera pa 1089, 1217 ndi 1790 cm-1, zomwe zimayambitsidwa ndi kugwedezeka kwa CH π (CH) kotambasula, CO ν (CO) kotambasula ndi C=O ν (C=O) kotambasula, 54, 55 motsatana. Nsonga zina za 1363 ndi 1592 cm-1 zimagwirizana ndi kugwedezeka kwa OCO kofanana νs(OCO) ndi kugwedezeka kwa OCO kosagwirizana νas(OCO)33.56 HCOO*, motsatana. Pamene kuyankha kukupitirira, nsonga za mitundu ya HCOOH* ndi HCOO* zimazimiririka pang'onopang'ono. Kawirikawiri, kuwonongeka kwa formic acid kumaphatikizapo magawo atatu akuluakulu: (I) kuyamwa kwa formic acid pamalo omwe akugwira ntchito, (II) kuchotsa H kudzera mu njira ya formate kapena carboxylate, ndi (III) kuphatikiza kwa H ziwiri zoyamwa kuti zipange haidrojeni. HCOO* ndi COOH* ndi zinthu zofunika kwambiri pakuzindikira njira za formate kapena carboxylate, motsatana57. Pogwiritsa ntchito njira yathu yothandizira, ndi HCOO* peak yokha yomwe imadziwika bwino yomwe idawonekera, zomwe zikusonyeza kuti kuwonongeka kwa formic acid kumachitika kudzera mu njira ya formic acid58 yokha. Zofananazo zidawonedwa pa kutentha kochepa kwa 78 °C ndi 88 °C (chithunzi S40).
Ma spectra a DRIFT a HCOOH dehydrogenation pa Co-SAs/NPs@NC-950 ndi b Co SAs. Nthanoyi imasonyeza nthawi zomwe zimachitika pamalopo. c Kusintha kwa kuchuluka kwa mpweya komwe kumapangidwa pogwiritsa ntchito ma reagents osiyanasiyana olembera isotope pakapita nthawi. d Deta ya Kinetic isotope effect.
Mayeso ofanana a DRIFT adachitika pazinthu zokhudzana ndi Co NP ndi Co SA kuti aphunzire za synergistic effect mu Co-SA/NPs@NC-950 (Zithunzi 5 b ndi S41). Zinthu zonsezi zikuwonetsa zochitika zofanana, koma nsonga za HCOOH* ndi HCOO* zasunthika pang'ono, zomwe zikusonyeza kuti kuyambitsidwa kwa Co NPs kumasintha kapangidwe ka zamagetsi ka malo a monoatomic. Nsonga ya νas(OCO) imawoneka mu Co-SAs/NPs@NC-950 ndi Co SA koma osati mu Co NPs, zomwe zikusonyezanso kuti pakati pomwe formic acid imawonjezeredwa ndi monodentate formic acid yolunjika pamwamba pa mchere. ndipo imamatiridwa pa SA ngati malo ogwirira ntchito 59. Ndikofunikira kudziwa kuti kuwonjezeka kwakukulu kwa kugwedezeka kwa nsonga za π(CH) ndi ν(C = O) kunawonedwa, zomwe zikuwoneka kuti zidapangitsa kuti HCOOH* isokonezeke ndikupangitsa kuti izi zichitike. Zotsatira zake, ma peaks a HCOOH* ndi HCOO* mu Co-SAs/NPs@NC adatsala pang'ono kuzimiririka patatha mphindi ziwiri, zomwe zimakhala zachangu kuposa za monometallic (mphindi 6) ndi nanoparticle-based catalysts (mphindi 12). Zotsatira zonsezi zimatsimikizira kuti nanoparticle doping imawonjezera kuyamwa ndi kuyambitsa kwa intermediates, motero imafulumizitsa zomwe zanenedwa pamwambapa.
Kuti tipitirize kusanthula njira yochitira zinthu ndikupeza sitepe yodziwira liwiro (RDS), zotsatira za KIE zidachitika pamaso pa Co-SAs/NPs@NC-950. Pano, ma isotope osiyanasiyana a formic acid monga HCOOH, HCOOD, DCOOH ndi DCOOD amagwiritsidwa ntchito pa maphunziro a KIE. Monga momwe zasonyezedwera pa Chithunzi 5c, kuchuluka kwa hydrogenation kumachepa motere: HCOOH > HCOOD > DCOOH > DCOOD. Kuphatikiza apo, mitengo ya KHCOOH/KHCOOD, KHCOOH/KDCOOH, KHCOOD/KDCOOD ndi KDCOOH/KDCOOD idawerengedwa ngati 1.14, 1.71, 2.16 ndi 1.44, motsatana (Chithunzi 5d). Motero, kusweka kwa CH bond mu HCOO* kumawonetsa ma kH/kD ​​>1.5, kusonyeza mphamvu yayikulu ya kinetic60,61, ndipo zikuwoneka kuti zikuyimira RDS ya HCOOH dehydrogenation pa Co-SAs/NPs@NC-950.
Kuphatikiza apo, mawerengedwe a DFT adachitika kuti amvetsetse momwe ma nanoparticles opangidwa ndi doped amakhudzira ntchito ya Co-SA. Ma Co-SAs/NPs@NC ndi Co-SA adapangidwira kutengera zoyeserera zomwe zawonetsedwa komanso ntchito zam'mbuyomu (Zithunzi 6a ndi S42)52,62. Pambuyo pa kukonza kwa geometric, ma nanoparticles ang'onoang'ono a Co6 (CoN2C2) omwe amakhala limodzi ndi mayunitsi a monoatomic adazindikirika, ndipo kutalika kwa ma bond a Co-C ndi Co-N mu Co-SA/NPs@NC kudapezeka kuti ndi 1.87 Å ndi 1.90 Å, motsatana. , zomwe zikugwirizana ndi zotsatira za XAFS. Kuchulukana kwa magawo owerengedwa (PDOS) kukuwonetsa kuti atomu imodzi yachitsulo ya Co ndi nanoparticle composite (Co-SAs/NPs@NC) zikuwonetsa kusakanikirana kwakukulu pafupi ndi mulingo wa Fermi poyerekeza ndi CoN2C2, zomwe zimapangitsa HCOOH. Kusamutsa kwa ma electron komwe kwawonongeka kumakhala kothandiza kwambiri (Zithunzi 6b ndi S43). Malo ofanana a d-band a Co-SAs/NPs@NC ndi Co-SA adawerengedwa kuti ndi -0.67 eV ndi -0.80 eV, motsatana, pomwe kuwonjezeka kwa Co-SAs/NPs@NC kunali 0.13 eV, zomwe zidapangitsa kuti NP itayamba, kulowetsedwa kwa tinthu ta HCOO* ndi kapangidwe ka electronic ka CoN2C2 kumachitika. Kusiyana kwa kuchuluka kwa mphamvu kukuwonetsa mtambo waukulu wa ma elekitironi kuzungulira block ya CoN2C2 ndi nanoparticle, zomwe zikusonyeza kuyanjana kwamphamvu pakati pawo chifukwa cha kusinthana kwa ma elekitironi. Kuphatikiza ndi kusanthula kwa mphamvu ya Bader, zidapezeka kuti Co yofalikira mwa atomiki idataya 1.064e mu Co-SA/NPs@NC ndi 0.796e mu Co SA (Chithunzi S44). Zotsatirazi zikuwonetsa kuti kuphatikiza kwa tinthu ta nanoparticles kumabweretsa kuchepa kwa ma elekitironi a malo a Co, zomwe zimapangitsa kuti Co valence iwonjezeke, zomwe zikugwirizana ndi zotsatira za XPS (Chithunzi 6c). Makhalidwe a kuyanjana kwa Co-O a HCOO adsorption pa Co-SAs/NPs@NC ndi Co SA adasanthulidwa powerengera gulu la Hamiltonian lozungulira la crystalline (COHP)63. Monga momwe zasonyezedwera pa Chithunzi 6 d, ma values ​​oipa ndi abwino a -COHP akugwirizana ndi mkhalidwe wa antibonding ndi mkhalidwe womangirira, motsatana. Mphamvu ya bond ya Co-O yomwe imakhudzidwa ndi HCOO (Co-carbonylOH HCOO*) idayesedwa pophatikiza ma values ​​a -COHP, omwe anali 3.51 ndi 3.38 a Co-SAs/NPs@NC ndi Co-SA, motsatana. Kumangirira kwa HCOOH kunawonetsanso zotsatira zofanana: kuwonjezeka kwa integral value ya -COHP pambuyo pa nanoparticle doping kumasonyeza kuwonjezeka kwa Co-O bonding, motero kulimbikitsa kuyambika kwa HCOO ndi HCOOH (Chithunzi S45).
Co-SA/NPs@NC-950 kapangidwe ka lattice. b PDOS Co-SA/NP@NC-950 ndi Co SA. c 3D isosurface ya kusiyana kwa mphamvu ya HCOOH adsorption pa Co-SA/NPs@NC-950 ndi Co-SA. (d) pCOHP ya ma bond a Co-O omwe akhudzidwa ndi HCOO pa Co-SA/NPs@NC-950 (kumanzere) ndi Co-SA (kumanja). e Njira yochitira ndi HCOOH dehydrogenation pa Co-SA/NPs@NC-950 ndi Co-SA.
Kuti timvetse bwino momwe Co-SA/NPs@NC imagwirira ntchito bwino kwambiri pakuchepa kwa madzi m'thupi, njira yochitira ndi mphamvu zake zinadziwika. Makamaka, kuchepa kwa madzi m'thupi m'thupi kumaphatikizapo magawo asanu, kuphatikizapo kusintha kwa HCOOH kukhala HCOOH*, HCOOH* kukhala HCOO* + H*, HCOO* + H* kukhala 2H* + CO2*, 2H* + CO2* kukhala 2H* + CO2, ndi 2H* mu H2 (Chithunzi 6e). Mphamvu yothira madzi m'thupi la mamolekyu a formic acid pamwamba pa catalyst kudzera mu mpweya wa carboxylic ndi yotsika kuposa kudzera mu hydroxyl oxygen (Zithunzi S46 ndi S47). Pambuyo pake, chifukwa cha mphamvu yotsika, adsorbate imadutsa mu OH bond cleavage kuti ipange HCOO* m'malo mwa CH bond cleavage kuti ipange COOH*. Nthawi yomweyo, HCOO* imagwiritsa ntchito monodentate adsorption, yomwe imalimbikitsa kusweka kwa ma bond ndi kupanga CO2 ndi H2. Zotsatirazi zikugwirizana ndi kukhalapo kwa νas(OCO) peak in in situ DRIFT, zomwe zikusonyezanso kuti kuwonongeka kwa FA kumachitika kudzera mu njira ya formate mu kafukufuku wathu. Ndikofunikira kudziwa kuti malinga ndi muyeso wa KIE, kugawanika kwa CH kuli ndi chotchinga champhamvu cha reaction kuposa njira zina zochitira ndipo kumayimira RDS. Chotchinga champhamvu cha optimal Co-SAs/NPs@NC catalyst system ndi chotsika ndi 0.86 eV kuposa cha Co-SA (1.2 eV), zomwe zimathandizira kwambiri ntchito yonse ya dehydrogenation. Chodziwika bwino ndi chakuti, kupezeka kwa nanoparticles kumawongolera kapangidwe ka zamagetsi ka malo ogawa ma atomu, komwe kumawonjezera kulowetsedwa ndi kuyatsidwa kwa zinthu zapakati, motero kumachepetsa chotchinga cha reaction ndikulimbikitsa kupanga kwa hydrogen.
Mwachidule, tikuwonetsa koyamba kuti mphamvu ya catalytic ya ma catalyst opanga hydrogen ikhoza kusinthidwa kwambiri pogwiritsa ntchito zipangizo zomwe zili ndi malo ogawa kwambiri a monometallic ndi tinthu tating'onoting'ono ta nano. Lingaliro ili latsimikiziridwa ndi kupanga ma catalyst achitsulo chimodzi omwe ali ndi cobalt omwe asinthidwa ndi tinthu tating'onoting'ono ta nano (Co-SAs/NPs@NC), komanso zinthu zina zokhudzana ndi malo ogawa okha achitsulo (CoN2C2) kapena Co NPs. Zipangizo zonse zinakonzedwa ndi njira yosavuta ya pyrolysis. Kusanthula kwa kapangidwe kake kukuwonetsa kuti catalyst yabwino kwambiri (Co-SAs/NPs@NC-950) imakhala ndi mayunitsi a CoN2C2 omwazikana ndi atomiki ndi tinthu tating'onoting'ono ta nano (7-8 nm) tomwe tili ndi nayitrogeni ndi graphite-like carbon. Ili ndi mpweya wabwino kwambiri wopangidwa mpaka 1403.8 ml g-1 h-1 (H2:CO2 = 1.01:1), H2 ndi CO kusankha kwa 99.96% ndipo imatha kukhala ndi ntchito yokhazikika kwa masiku angapo. Ntchito ya catalyst iyi imaposa ntchito ya ma catalyst ena a Co SA ndi Pd/C ndi nthawi 4 ndi 15 motsatana. Mayeso a DRIFT omwe ali pamalopo akuwonetsa kuti poyerekeza ndi Co-SA, Co-SAs/NPs@NC-950 ikuwonetsa kulowetsedwa kwamphamvu kwa HCOO*, komwe ndikofunikira pa njira ya formate, ndipo ma nanoparticles a dopant amatha kulimbikitsa kuyambitsa kwa HCOO* ndi kufulumira kwa C-H. Kugawanika kwa bond kunadziwika kuti RDS. Mawerengedwe a chiphunzitso akuwonetsa kuti Co NP doping imawonjezera pakati pa d-band ya maatomu a Co imodzi ndi 0.13 eV kudzera mu kuyanjana, kukulitsa kulowetsedwa kwa ma intermediates a HCOOH* ndi HCOO*, potero kuchepetsa chotchinga cha reaction kuchokera pa 1.20 eV ya Co SA kufika pa 0 .86 eV. Iye ndiye amene amachititsa bwino kwambiri.
Mwachidule, kafukufukuyu akupereka malingaliro opangira zinthu zatsopano zoyambitsa chitsulo cha atomu imodzi ndipo akupititsa patsogolo kumvetsetsa momwe mungakulitsire magwiridwe antchito a catalytic kudzera mu synergistic effect ya malo achitsulo amitundu yosiyanasiyana. Tikukhulupirira kuti njira iyi ikhoza kufalikira mosavuta kuzinthu zina zambiri zoyambitsa chitsulo.
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%) idagulidwa ku McLean, China. Formic acid (HCOOH, 98%) idagulidwa ku Rhawn, China. Ma reagents onse adagwiritsidwa ntchito mwachindunji popanda kuyeretsa kwina, ndipo madzi oyera kwambiri adakonzedwa pogwiritsa ntchito njira yoyeretsera yoyera kwambiri. Pt/C (5% yokweza) ndi Pd/C (5% yokweza) zidagulidwa ku Sigma-Aldrich.
Kupanga ma nanocrystals a CoZn-ZIF kunachitika kutengera njira zakale ndi zosintha zina23,64. Choyamba, 30 mmol Zn(NO3)2·6H2O (8.925 g) ndi 3.5 mmol Co(NO3)2·6H2O (1.014 g) zinasakanizidwa ndikusungunuka mu 300 ml ya methanol. Kenako, 120 mmol ya 2-methylimidazole (9.853 g) inasungunuka mu 100 ml ya methanol ndikuwonjezeredwa ku yankho lomwe lili pamwambapa. Chosakanizacho chinasakanizidwa kutentha kwa chipinda kwa maola 24. Pomaliza, mankhwalawa adalekanitsidwa ndi centrifugation pa 6429 g kwa mphindi 10 ndikutsukidwa bwino ndi methanol katatu. Ufa womwe unatuluka unaumitsidwa mu vacuum pa 60°C usiku wonse musanagwiritse ntchito.
Kuti apange Co-SAs/NPs@NC-950, ufa wouma wa CoZn-ZIF unapakidwa pa 950 °C kwa ola limodzi mu mpweya wa 6% H2 + 94% Ar, ndi kutentha kwa 5 °C/min. Kenako chitsanzocho chinazizidwa kutentha kwa chipinda kuti chipeze Co-SA/NPs@NC-950. Pa Co-SAs/NPs@NC-850 kapena Co-SAs/NPs@NC-750, kutentha kwa pyrolysis kunasinthidwa kufika pa 850 ndi 750 °C, motsatana. Zitsanzo zokonzedwa zingagwiritsidwe ntchito popanda kukonza kwina, monga kupukuta asidi.
Kuyeza kwa TEM (transmission electron microscopy) kunachitika pa Thermo Fisher Titan Themis 60-300 "cube" microscope yokhala ndi chowongolera chithunzi ndi lenzi yopangira probe ya 300 kV. Kuyesa kwa HAADF-STEM kunachitika pogwiritsa ntchito ma microscope a FEI Titan G2 ndi FEI Titan Themis Z okhala ndi ma probes ndi ma image correctors, ndi ma DF4 four-segment detectors. Zithunzi za EDS elemental mapping zinapezekanso pa FEI Titan Themis Z microscope. Kusanthula kwa XPS kunachitika pa X-ray photoelectron spectrometer (Thermo Fisher model ESCALAB 250Xi). XANES ndi EXAFS Co K-edge spectra zinasonkhanitsidwa pogwiritsa ntchito tebulo la XAFS-500 (China Spectral Instruments Co., Ltd.). Kuchuluka kwa Co kunatsimikiziridwa ndi atomic absorption spectroscopy (AAS) (PinAAcle900T). Ma spectra a X-ray diffraction (XRD) adajambulidwa pa X-ray diffractometer (Bruker, Bruker D8 Advance, Germany). Ma isotherms a nayitrogeni adsorption adapezeka pogwiritsa ntchito chipangizo choyezera (Micromeritics, ASAP2020, USA).
Kuchepa kwa madzi m'thupi kunachitika mumlengalenga wa argon ndipo mpweya unachotsedwa motsatira njira ya Schlenk. Chotengera cha reaction chinachotsedwamo ndikudzazidwanso ndi argon kasanu ndi kamodzi. Yatsani madzi a condenser ndikuwonjezera catalyst (30 mg) ndi solvent (6 ml). Tenthetsani chidebecho kutentha komwe mukufuna pogwiritsa ntchito thermostat ndikuchilola kuti chigwirizane kwa mphindi 30. Formic acid (10 mmol, 377 μL) kenako inawonjezedwa ku chotengera cha reaction pansi pa argon. Tembenuzani valavu ya burette ya njira zitatu kuti muchepetse kupsinjika kwa reactor, muitsekenso, ndikuyamba kuyeza kuchuluka kwa mpweya wopangidwa pogwiritsa ntchito burette yamanja (Chithunzi S16). Pambuyo pa nthawi yofunikira kuti reaction ithe, chitsanzo cha mpweya chinasonkhanitsidwa kuti chisanthulidwe cha GC pogwiritsa ntchito sirinji yosagwira mpweya yotsukidwa ndi argon.
Mayeso a DRIFT anachitika pa Fourier transform infrared (FTIR) spectrometer (Thermo Fisher Scientific, Nicolet iS50) yokhala ndi chowunikira cha mercury cadmium telluride (MCT). Ufa wa catalyst unayikidwa mu selo yochitira zinthu (Harrick Scientific Products, Praying Mantis). Pambuyo pochiza chothandizira ndi mtsinje wa Ar (50 ml/min) kutentha kwa chipinda, chitsanzocho chinatenthedwa kufika kutentha komwe kwapatsidwa, kenako chinapakidwa ndi Ar (50 ml/min) mu yankho la HCOOH ndikutsanuliridwa mu selo yochitira zinthu mkati. kuti chichite zinthu. Chitsanzo cha njira zosiyanasiyana zochizira. Ma spectra a infrared adalembedwa nthawi zosiyanasiyana kuyambira masekondi 3.0 mpaka ola limodzi.
HCOOH, DCOOH, HCOOD ndi DCOOD zimagwiritsidwa ntchito ngati zinthu zomwe zimagwiritsidwa ntchito mu propylene carbonate. Zinthu zina zonse zimagwirizana ndi njira yochotsera madzi m'thupi ya HCOOH.
Kuwerengera mfundo zoyamba kunachitika pogwiritsa ntchito njira ya density functional theory framework mkati mwa Vienna Ab initio modeling package (VASP 5.4.4) 65,66. Selo ya superunit yokhala ndi graphene surface (5 × 5) yokhala ndi transverse dimension ya pafupifupi 12.5 Å idagwiritsidwa ntchito ngati substrate ya CoN2C2 ndi CoN2C2-Co6. Mtunda wa vacuum woposa 15 Å udawonjezedwa kuti upewe kuyanjana pakati pa zigawo za substrate zomwe zili pafupi. Kuyanjana pakati pa ma ayoni ndi ma electron kumafotokozedwa ndi njira ya projected amplified wave (PAW)65,67. Ntchito ya Perdue-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) yokhala ndi van der Waals correction yomwe yaperekedwa ndi Grimm68,69 idagwiritsidwa ntchito. Zofunikira za convergence za total energy ndi force ndi 10−6 eV/atomu ndi 0.01 eV/Å. Kudula mphamvu kunayikidwa pa 600 eV pogwiritsa ntchito gridi ya Monkhorst-Pack 2 × 2 × 1 K-point. Pseudopotential yomwe imagwiritsidwa ntchito mu chitsanzochi imapangidwa kuchokera ku kasinthidwe ka zamagetsi kupita ku C 2s22p2 state, N 2s22p3 state, Co 3d74s2 state, H 1 s1 state, ndi O 2s22p4 state. Kusiyana kwa mphamvu ya adsorption ndi kuchuluka kwa ma electron kumawerengedwa pochotsa mphamvu ya gasi ndi mitundu ya pamwamba kuchokera ku mphamvu ya adsorption system malinga ndi adsorption kapena interface models70,71,72,73,74. Kukonza mphamvu ya Gibbs free kumagwiritsidwa ntchito kusintha mphamvu ya DFT kukhala mphamvu ya Gibbs free ndipo kumaganizira zopereka za vibrational ku entropy ndi zero point energy75. Njira yokwezeka ya chithunzi-nudging elastic band (CI-NEB) idagwiritsidwa ntchito pofufuza momwe kusintha kwa reaction76 kulili.
Deta yonse yomwe yapezedwa ndi kusanthula panthawi ya kafukufukuyu yaphatikizidwa mu nkhaniyi ndi zina zowonjezera kapena imapezeka kwa wolemba woyenerera ngati pakufunika kutero. Deta yochokera ku nkhaniyi yaperekedwa.
Makhodi onse omwe agwiritsidwa ntchito mu zoyeserera zomwe zili ndi nkhaniyi akupezeka kwa olemba omwe akugwirizana nawo akapemphedwa.
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