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Kev tsim thiab kev loj hlob ntawm kev ua tau zoo catalysts tau txais kev saib xyuas ntau hauv cov kev xaiv hydrogenation tab sis tseem yog ib qho kev sib tw loj.Ntawm no peb qhia txog monatomic RuNi alloy (SAA) uas tus neeg Ru atoms raug immobilized rau saum npoo ntawm Ni nanoparticles ntawm Ru-Ni kev koom tes, uas yog nrog los ntawm kev hloov hluav taws xob los ntawm subsurface Ni mus rau Ru.Rau peb txoj kev paub, qhov zoo tshaj plaws catalyst 0.4% RuNi SAA ib txhij pom kev ua haujlwm siab dua (TOF tus nqi: 4293 h-1) thiab chemoselectivity rau kev xaiv hydrogenation ntawm 4-nitrostyrene rau 4-aminostyrene (yield:> 99%), qib siab tshaj plaws los ntawm piv nrog cov paub heterogeneous catalysts.Nyob rau hauv situ thwmsim thiab theoretical xam qhia tau hais tias lub Ru-Ni interface qhov chaw, raws li nyob rau hauv lub active sites, txhawb kev nyiam ua txhaum ntawm NO bonds nrog ib tug qis zog barrier ntawm 0.28 eV.Tsis tas li ntawd, synergistic Ru-Ni catalysis nyiam tsim cov khoom nruab nrab (C8H7NO * thiab C8H7NOH*) thiab ua kom cov qib ntsuas tus nqi (hydrogenation ntawm C8H7NOH *).
Functionalized aromatic amines, lub tsev tseem ceeb ntawm cov tshuaj zoo, muaj cov ntaub ntawv tseem ceeb hauv kev tsim tshuaj, agrochemicals, pigments thiab polymers1,2,3.Lub catalytic hydrogenation ntawm cov khoom muaj nitroaromatic uas muaj nyob rau hauv heterogeneous catalysts tau nyiam cov xim zoo nkauj raws li ib puag ncig tus phooj ywg thiab rov ua dua tshiab rau kev sib txuas ntawm amines nrog tus nqi ntxiv 4,5,6,7.Txawm li cas los xij, chemoselective txo qis ntawm -NO2 pawg thaum khaws lwm pawg txo qis xws li alkenes, alkynes, halogens, lossis ketones yog qhov xav tau tab sis nyuaj ua haujlwm 8,9,10,11.Yog li ntawd, kev siv cov heterogeneous catalysts rau qhov kev txo qis ntawm -NO2 pawg yam tsis muaj kev cuam tshuam rau lwm cov nyiaj txo qis yog qhov xav tau 12,13,14.Ntau cov noble-hlau-dawb catalysts tau tshawb xyuas los catalyze hydrogenation ntawm nitroarenes, tab sis cov tshuaj tiv thaiv hnyav tiv thaiv lawv daim ntawv thov dav 15,16.Txawm hais tias muaj zog hlau catalysts (xws li Ru17, Pt18, 19, 20 los yog Pd21, 22, 23) yog nquag nyob rau hauv cov tshuaj tiv thaiv me me, lawv feem ntau raug kev txom nyem los ntawm tus nqi siab, kev xaiv zoo tshaj plaws, thiab kev siv atom tsawg.Yog li, tau txais kev ua haujlwm siab thiab chemoselective catalysts los ntawm kev tsim qauv tsim nyog thiab kev kho kom zoo ntawm cov qauv zoo tseem yog ib qho kev sib tw loj24,25,26.
Monatomic Alloy (SAA) catalysts muaj qhov ua tau zoo ntawm cov hlau zoo tshaj plaws, cov qauv geometric tshwj xeeb thiab hluav taws xob, muab qhov chaw tshwj xeeb, thiab muab kev ua haujlwm zoo catalytic los ntawm kev ua txhaum cov yam ntxwv ntawm kev ntsuas tus cwj pwm 27,28,29,30,31.Doped ib leeg atoms thiab host hlau atoms hauv SAA tuaj yeem ua haujlwm ua ob qhov chaw ua haujlwm, ua kom yooj yim rau kev ua haujlwm ntawm ntau lub substrates lossis tso cai rau cov theem pib sib txawv tshwm sim ntawm qhov chaw sib txawv32,33,34.Tsis tas li ntawd, kev sib koom ua ke ntawm heterometallic sib cais ntawm cov hlau tsis huv ntawm cov atoms thiab cov khoom siv hlau tuaj yeem ua rau idiosyncratic synergistic cov teebmeem, txawm hais tias kev nkag siab ntawm cov teebmeem zoo li no ntawm ob pawg ntawm cov chaw hlau ntawm qib atomic tseem muaj teeb meem 35,36,37,38.Rau hydrogenation ntawm functionalized nitroarenes, hluav taws xob thiab geometric qauv ntawm active site yuav tsum tau tsim nyob rau hauv xws li ib txoj kev raws li kom ceev lub activation ntawm tsuas yog nitro pawg.Raws li txoj cai, pawg electron-deficient nitro feem ntau yog adsorbed ntawm thaj chaw nucleophilic ntawm cov catalyst nto, thaum nyob rau hauv txoj kev hydrogenation tom ntej, kev koom tes catalysis ntawm cov chaw nyob sib ze yuav ua lub luag haujlwm tseem ceeb hauv kev tswj cov reactivity thiab chemoselectivity4,25.Qhov no tau ua rau peb tshawb nrhiav SAA catalysts raws li tus neeg sib tw tau zoo rau kev txhim kho cov catalytic efficiency ntawm chemoselective hydrogenation ntawm nitroaromatic compounds, ntxiv rau ntxiv elucidating kev sib raug zoo ntawm active site qauv thiab atomic scale catalytic kev ua tau zoo.
Ntawm no, catalysts raws li monatomic RuNi alloys tau npaj raws li ob-theem hluavtaws mus kom ze, nrog rau cov qauv-topological transformation ntawm ib txheej ob txheej hydroxide (LDH) ua raws li electro-tshem tawm kev kho mob.RuNi SAA nthuav tawm tshwj xeeb catalytic efficiency (> 99% yield) rau chemoselective hydrogenation ntawm 4-nitrostyrene rau 4-aminostyrene nrog ib tug turnover zaus (TOF) txog li ~ 4300 mol-mol Ru-1 h-1, uas yog siab tshaj. theem ntawm heterogeneous catalysts sau npe nyob rau hauv cov xwm txheej zoo sib xws.Electron microscopy thiab spectroscopic characterization pom tau hais tias cais Ru atoms dispersed nyob rau saum npoo ntawm Ni nanoparticles (~ 8 nm), tsim ib tug ruaj khov Ru-Ni kev sib koom ua ke, uas ua rau tsis zoo Ru chaw (Ruδ-) vim electron hloov los ntawm subsurface Ni rau Ru. .Nyob rau hauv situ FT-IR, XAFS kev tshawb fawb thiab qhov ceev functional theory (DFT) xam tau lees paub tias qhov chaw ntawm Ru-Ni interface raws li cov chaw ua haujlwm sab hauv pab txhawb nitro.Activated adsorption (0.46 eV) txawv ntawm cov monometallic nickel catalyst.(0.74 eV).Tsis tas li ntawd, hydrogen dissociation tshwm sim nyob rau hauv cov hauj lwm Ni nyob sib ze, ua raws li hydrogenation ntawm intermediates (C8H7NO * thiab C8H7NOH *) nyob rau hauv Ruδ txoj hauj lwm.Kev sib koom ua ke ntawm kev txhawb nqa doping hauv RuNi SAA catalyst ua rau muaj txiaj ntsig zoo ntawm nitroarenes hydrogenation kev ua haujlwm thiab kev xaiv, uas tuaj yeem txuas ntxiv mus rau lwm yam tsis tshua muaj txiaj ntsig hlau catalysts siv hauv cov qauv rhiab heev.
Raws li kev hloov pauv ntawm cov txheej txheem topology ntawm txheej txheej ob hydroxide (LDH) precursors, peb npaj monometallic Ni tso rau ntawm amorphous Al2O3 substrates.Tom qab ntawd, ib txheej ntawm RuNi / Al2O3 cov qauv bimetallic nrog cov ntsiab lus Ru sib txawv (0.1-2 wt %) tau raug tsim los ntawm electrodisplacement kom tso Ru atoms rau saum npoo ntawm Ni nanoparticles (NPs) (Fig. 1a).Inductively coupled plasma atomic emission spectrometry (ICP-AES) kev ntsuas kom meej meej muab cov ntsiab lus ntawm Ru thiab Ni nyob rau hauv cov qauv no (Cov Lus Qhia Ntxiv 1), uas yog nyob ze rau qhov theoretical feedstock loading.Cov duab SEM (Cov duab ntxiv 1) thiab BET cov txiaj ntsig (Cov duab ntxiv 2–9 thiab Cov Lus Ntxiv 1) qhia meej tias cov qauv morphological thiab thaj chaw tshwj xeeb ntawm cov qauv RuNi / Al2O3 tsis dhau qhov kev hloov pauv hauv kev kho electrochemical.- cov txheej txheem txav.X-ray qauv (Fig. 1b) qhia ib tug series ntawm cov yam ntxwv reflections ntawm 2θ 44.3°, 51.6°, thiab 76.1°, qhia theem (111), (200), thiab (220) ntawm raug Ni (JCPDS 004–0850). ).Qhov zoo tshaj plaws, cov qauv RuNi tsis qhia qhov kev xav ntawm cov hlau lossis oxidized Ru, qhia tias muaj kev tawg ntau ntawm Ru ntau yam.Kev sib kis electron microscopy (TEM) kev ntsuas ntawm monometallic Ni thiab RuNi cov qauv (Daim duab 1c1-c8) qhia tias cov nickel nanoparticles zoo dispersed thiab immobilized ntawm amorphous Al2O3 kev txhawb nqa nrog cov particle loj sib xws (7.7–8.3 nm).HRTEM cov duab (Fig. 1d1–d8) qhia lub sij hawm sib xws ntawm lattice ntawm 0.203 nm nyob rau hauv cov qauv Ni thiab RuNi, sib xws rau Ni(111) dav hlau, txawm li cas los xij, lub lattice ntug ntawm Ru hais tsis tuaj.Qhov no qhia tau hais tias Ru atoms tau tawg heev ntawm cov qauv saum npoo thiab tsis cuam tshuam rau lub sijhawm Ni lattice.Meanwhile, 2 wt% Ru / Al2O3 yog synthesized los ntawm txoj kev deposition-deposition raws li ib tug tswj, nyob rau hauv uas Ru pawg tau uniformly faib rau saum npoo ntawm Al2O3 substrate (Ntxiv daim duab 10-12).
ib lub tswv yim ntawm txoj kev sib txuas rau RuNi / Al2O3 cov qauv, b X-ray diffraction qauv ntawm Ni / Al2O3 thiab ntau yam RuNi / Al2O3 qauv.c1−c8 TEM thiab d1−d8 HRTEM grating dluab nrog ntsig txog particle loj distributions ntawm monometallic Ni, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0, 8% wt., 1 wt.Daim duab kab txaij.% thiab 2 wt.% RuNi."au" txhais tau tias arbitrary units.
Kev ua haujlwm catalytic ntawm RuNi cov qauv tau kawm los ntawm chemoselective hydrogenation ntawm 4-nitrostyrene (4-NS) rau 4-aminostyrene (4-AS).Kev hloov pauv 4-NS ntawm cov ntshiab Al2O3 substrate tsuas yog 0.6% tom qab 3 teev (Table 2), qhia me ntsis catalytic nyhuv ntawm Al2O3.Raws li qhia hauv daim duab.2a, tus thawj nickel catalyst tau nthuav tawm cov kev ua haujlwm catalytic tsawg heev nrog 4-NS hloov dua siab tshiab ntawm 7.1% tom qab 3 teev, thaum 100% kev hloov pauv tuaj yeem ua tiav nyob rau hauv lub xub ntiag ntawm monometallic Ru catalyst nyob rau hauv tib lub sijhawm.Tag nrho RuNi catalysts tau pom tias muaj kev ua kom muaj zog hydrogenation (hloov pauv: ~ 100%, 3 h) piv rau cov qauv monometallic, thiab cov tshuaj tiv thaiv tau zoo sib xws nrog Ru cov ntsiab lus.Qhov no txhais tau hais tias Ru hais ua lub luag haujlwm txiav txim siab hauv cov txheej txheem hydrogenation.Interestingly, cov khoom selectivity (Fig. 2b) nws txawv heev nyob ntawm tus catalyst.Rau qhov tsis tshua muaj siab ntshiab npib tsib xee catalyst, cov khoom tseem ceeb yog 4-nitroethylbenzene (4-NE) (selectivity: 83.6%) thiab kev xaiv ntawm 4-AC yog 11.3%.Nyob rau hauv cov ntaub ntawv ntawm monometallic Ru, C = C daim ntawv cog lus nyob rau hauv 4-NS yog ntau raug rau hydrogenation tshaj -NO2, ua rau tsim ntawm 4-nitroethylbenzene (4-NE) los yog 4-aminoethylbenzene (4-AE);kev xaiv ntawm 4-AC tsuas yog 15.7%.Kuj ceeb tias, RuNi catalysts nrog cov ntsiab lus Ru tsawg (0.1-0.4 wt%) tau pom zoo xaiv (> 99%) rau 4-aminostyrene (4-AS), qhia tias nws yog NO2 thiab tsis yog vinyl, yog tshwj xeeb chemoselective.Thaum cov ntsiab lus ntawm Ru ntau tshaj 0.6 wt.%, qhov kev xaiv ntawm 4-AS poob qis nrog nce loading ntawm Ru, thaum lub selectivity ntawm 4-AE nce ntxiv.Rau cov catalyst muaj 2 wt% RuNi, ob qho tib si nitro thiab vinyl pawg tau hydrogenated nrog kev xaiv siab rau 4-AE ntawm 98%.Txhawm rau kawm txog cov txiaj ntsig ntawm Ru dispersion xeev ntawm cov tshuaj tiv thaiv catalytic, 0.4 wt% Ru / Al2O3 cov qauv tau npaj (Cov duab ntxiv 10, 13 thiab 14) uas Ru hais feem ntau tau tawg ua ib tus neeg atoms ua raws li ob peb pawg Ru.(quasi-atomic Ru).Qhov kev ua tau zoo catalytic (Table 2) qhia tau hais tias 0.4 wt% Ru / Al2O3 txhim kho 4-AS selectivity (67.5%) piv rau 2 wt% Ru / Al2O3 qauv, tab sis qhov kev ua haujlwm tsis tshua muaj (kev hloov pauv: 12.9).%;3 teev).Raws li tag nrho cov hlau qhov chaw ntawm qhov chaw txiav txim siab los ntawm CO pulsed chemisorption ntsuas, qhov kev hloov pauv zaus (TOFmetal) ntawm RuNi catalyst tau txais qis dua 4-NS hloov dua siab tshiab (Cov duab ntxiv 15), uas pom qhov sib txawv ua ntej kom nce. thiab tom qab ntawd kom txo qis nrog kev nce hauv Ru loading (Ntxiv daim duab 16).Qhov no qhia tias tsis yog txhua qhov chaw hlau saum npoo ua raws li cov chaw nquag nquag rau RuNi catalysts.Tsis tas li ntawd, TOF ntawm RuNi catalyst raug xam los ntawm cov chaw Ru mus ntxiv nthuav tawm nws cov kev ua haujlwm hauv cov catalytic (Fig. 2c).Raws li cov ntsiab lus ntawm Ru nce los ntawm 0.1 wt.% mus rau 0.4 wt.% RuNi catalysts pom yuav luag tas mus li TOF qhov tseem ceeb (4271-4293 h-1), uas qhia txog thaj chaw ntawm Ru hais hauv atomic dispersion (tejzaum nws nrog kev tsim ntawm RuNi SAA).) thiab ua haujlwm raws li lub vev xaib tseem ceeb.Txawm li cas los xij, nrog kev nce ntxiv hauv kev thauj khoom ntawm Ru (hauv 0.6-2 wt %), TOF tus nqi txo qis, uas qhia tau tias muaj kev hloov pauv hauv cov qauv hauv nruab nrab ntawm lub chaw ua haujlwm (los ntawm atomic dispersion mus rau Ru nanoclusters).Ntxiv rau, rau peb txoj kev paub, TOF ntawm 0.4 wt% RuNi (SAA) catalyst yog nyob rau theem siab tshaj plaws ntawm cov hlau catalysts yav dhau los tau tshaj tawm nyob rau hauv cov xwm txheej zoo sib xws (Table 3), ntxiv qhia tias monoatomic RuNi alloys muab cov khoom zoo heev catalytic.tsom iav.Ntxiv daim duab 17 qhia cov catalytic kev ua tau zoo ntawm 0.4 wt% RuNi (SAA) catalyst ntawm ntau lub siab thiab kub ntawm H2, qhov twg H2 siab ntawm 1 MPa thiab cov tshuaj tiv thaiv kub ntawm 60 ° C tau siv los ua cov tshuaj tiv thaiv zoo.qauv muaj RuNi 0.4 wt.%.X-ray thiab TEM cov duab ntawm 0.4 wt% RuNi catalyst siv tom qab 5 lub voj voog (Cov duab ntxiv 18 thiab 19) tsis pom qhov hloov pauv tseem ceeb hauv cov qauv siv lead ua, qhia tias muaj kev ruaj ntseg siab ntawm cov tshuaj tiv thaiv hydrogenation.Tsis tas li ntawd, 0.4 wt% RuNi (SAA) catalyst kuj muab cov txiaj ntsig zoo ntawm amines rau chemoselective hydrogenation ntawm lwm cov nitroaromatic compounds uas muaj halogens, aldehydes, thiab hydroxyl pawg (Cov Lus Ntxiv 4), ua kom pom nws qhov kev siv tau zoo.
Catalytic hloov dua siab tshiab thiab b faib ntawm 4-nitrostyrene hydrogenation cov khoom nyob rau hauv lub xub ntiag ntawm monometallic Ni, Ru, thiab RuNi catalysts nrog sib txawv Ru ntsiab lus (0.1-2 wt%), c nyob rau hauv lub catalytic dynamic ntau, Turnover zaus (TOF) ntawm RuNi catalysts c nyob ntawm Ru ib mole.d Kev sim rau qhov muaj peev xwm rov qab siv tau ntawm 0.4 wt.% RuNi catalyst rau tsib lub voj voog catalytic sib law liag.ln (C0 / C) yog raws li lub sijhawm tshuaj tiv thaiv ntawm hydrogenation ntawm e-nitrobenzene thiab f-styrene nrog kev sib xyaw ntawm nitrobenzene thiab styrene (1: 1).Cov tshuaj tiv thaiv: 1 mmol reagent, 8 ml hnyav (ethanol), 0.02 g catalyst, 1 MPa H2, 60 ° C, 3 teev.Cov kab yuam kev raug txhais raws li tus qauv sib txawv ntawm peb qhov rov ua dua.
Txhawm rau tshawb xyuas qhov sib txawv tseem ceeb ntawm chemoselective, hydrogenation ntawm kev sib xyaw ntawm styrene thiab nitrobenzene (1: 1) kuj tau ua nyob rau hauv lub xub ntiag ntawm monometallic catalysts Ni, Ru, 0.4 wt% RuNi, thiab 2 wt% RuNi, feem. . 20).Txawm hais tias chemoselectivity ntawm cov tshuaj tiv thaiv hydrogenation ntawm cov pab pawg ua haujlwm zoo ib yam, muaj tseeb muaj qee qhov sib txawv hauv kev xaiv ntawm intramolecular thiab intermolecular hydrogenation vim molecular allosteric teebmeem.Raws li qhia hauv daim duab.2e, f, qhov nkhaus ln (C0 / C) piv rau lub sij hawm cov tshuaj tiv thaiv muab ib txoj kab ncaj nraim los ntawm lub hauv paus chiv keeb, qhia tias ob qho tib si nitrobenzene thiab styrene yog pseudo-thawj qhov kev txiav txim.Monometallic npib tsib xee catalysts pom tias tsis tshua muaj hydrogenation tus nqi tsis tu ncua rau ob qho tib si p-nitrobenzene (0.03 h-1) thiab styrene (0.05 h-1).Qhov tseem ceeb, qhov kev nyiam tshaj plaws styrene hydrogenation kev ua si (tus nqi tas li: 0.89 h-1) tau ua tiav ntawm Ru monometallic catalyst, uas yog ntau dua li cov kev ua ntawm nitrobenzene hydrogenation (tus nqi tas li: 0.18 h-1).Nyob rau hauv cov ntaub ntawv ntawm ib tug catalyst muaj RuNi (SAA) 0.4 wt.% nitrobenzene hydrogenation yog dynamically zoo dua styrene hydrogenation (tus nqi tas li: 1.90 h-1 vs. 0.04 h-1), qhia txog kev nyiam rau pawg -NO2.tshaj C hydrogenation = daim ntawv cog lus C. Rau cov catalyst nrog 2 wt.% RuNi, tus nqi tas li ntawm hydrogenation ntawm nitrobenzene (1.65 h-1) txo qis piv rau 0.4 wt.% RuNi (tab sis tseem siab dua li cov mono-hlau catalyst), thaum lub hydrogenation tus nqi ntawm styrene nce ntau (tus nqi tas li: 0.68).h-1).Qhov no kuj qhia tau hais tias nrog kev sib koom ua ke ntawm Ni thiab Ru, cov kev ua haujlwm catalytic thiab chemoselectivity ntawm -NO2 pawg tau nce ntau dua piv rau RuNi SAA.
Txhawm rau pom kev txiav txim siab lub xeev dispersion ntawm Ru thiab Ni cov tebchaw, ib txoj hauv kev siv cov duab siab lub nplhaib tsaus nti scanning electron microscopy nrog aberration kho (AC-HAADF-STEM) thiab lub ntsiab lus qhia los ntawm lub zog dispersive spectroscopy (EDS) tau ua.EMF elemental daim duab qhia ntawm tus qauv nrog 0.4 wt% RuNi cov ntsiab lus (Fig. 3a, b) qhia tau hais tias Ru yog heev uniformly dispersed ntawm cov nickel nanoparticles, tab sis tsis nyob rau hauv lub Al2O3 substrate, coj AC-HAADF-STEM duab (Fig. 3c) qhia tau hais tias, Nws tuaj yeem pom tau tias qhov chaw ntawm Ni NPs muaj ntau qhov chaw ci ntsa iab ntawm atomic loj ntawm Ru atoms (cim los ntawm xiav xub), thaum tsis pom cov pawg lossis Ru nanoparticles.Daim duab 3d), qhia txog kev tsim cov monatomic RuNi alloys.Rau ib qho piv txwv uas muaj RuNi 0.6 wt.%.Nyob rau hauv cov ntaub ntawv ntawm ib tug qauv nrog 2 wt% RuNi cov ntsiab lus, ntau pawg loj Ru ntawm Ni NPs tau pom nyob rau hauv daim duab HAADF-STEM (Fig. 3f) thiab EDS elemental mapping (Ntxiv daim duab 21), qhia txog qhov loj ntawm Ru. .
ib daim duab HAADF-STEM, b coj EDS daim duab kos duab, c siab daws teeb meem AC-HAADF-STEM duab, d magnified STEM duab thiab sib piv siv zog faib ntawm 0.4 wt% RuNi qauv.(e, f) AC-HAADF-STEM cov duab ntawm cov qauv uas muaj 0.6 wt.% RuNi thiab 2 wt.% RuNi, raws.
Piv rau Ni / Al2O3 thiab Ru / Al2O3 cov qauv, DRIFTS spectra ntawm CO adsorption nyob rau hauv situ tau ua (Fig. 4a) mus kawm ntxiv txog cov qauv ntawm cov qauv uas muaj 0.4 wt.yog ', 0,6 wt.% thiab 2 wt.% RuNi.CO adsorption ntawm tus qauv Ru / Al2O3 muab lub ntsiab ncov ntawm 2060 cm-1 thiab lwm qhov siab siab ntawm 1849 cm-1 vim yog cov kab CO adsorption ntawm Ru thiab txuas rau ob lub zeem muag Ru atoms, raws li CO39,40.Rau cov qauv monometallic Ni, lub ncov muaj zog tsuas yog pom ntawm 2057 cm–1, uas yog vim li cas rau cov kab CO41,42 hauv cheeb tsam npib tsib xee.Rau cov qauv RuNi, ntxiv rau lub ncov tseem ceeb ntawm 2056 cm-1, muaj qhov sib txawv ntawm lub xub pwg ntawm ~ 2030 cm-1.Txoj kev Gaussian ncov haum yog siv los txiav txim siab qhov kev faib tawm ntawm RuNi cov qauv hauv thaj tsam 2000-2100 cm-1 thiab faib cov CO hauv thaj av Ni (2056 cm-1) thiab Ru (2031-2039 cm) cheeb tsam.Ob lub ncov yog linearly adsorbed – 1) (Fig. 4b).Interestingly, los ntawm cov qauv Ru / Al2O3 (2060 cm–1) mus rau cov qauv RuNi (2031–2039 cm–1), cov linearly cuam tshuam CO ncov nyob rau hauv cheeb tsam Ru undergoes ib tug tseem ceeb redshift thiab nce nrog nce Ru ntsiab lus.Qhov no qhia tau hais tias muaj zog electronegativity ntawm Ru hais nyob rau hauv cov qauv RuNi, uas yog tshwm sim los ntawm electron hloov ntawm Ni mus rau Ru, nce lub d-π electron tawm tswv yim los ntawm Ru mus rau lub antibonding CO 2π * orbital.Tsis tas li ntawd, rau ib qho piv txwv uas muaj 0.4 pawg% RuNi, tsis muaj kev sib txuas adsorption ncov tau pom, qhia tias Ru hais muaj nyob raws li cais Ni atoms (SAA).Nyob rau hauv cov ntaub ntawv ntawm cov qauv nrog 0.6 wt.% RuNi thiab 2 wt.%.
a In situ CO-DRIFTS spectra of Ni/Al2O3, Ru/Al2O3 and 0.4 wt.%, 0.6 wt.%, 2 wt.% RuNi samples with helium gas flow in the range 2100–1500 cm-1 for 20 min.b Scaled thiab Gaussian-fitted spectra ntawm tus qauv RuNi / Al2O3 nrog cov haujlwm ruaj khov thiab FWHM.c Nyob rau hauv situ Ru K-edge XANES spectra thiab d EXAFS Fourier hloov spectra ntawm ntau yam qauv.K2-weighted wavelet transform ntawm XAFS K-edge Ru signals raws li Morlet wavelet rau e Ru qauv los ntawm e Ru foil, f 0.4 wt% RuNi thiab g RuO2."au" txhais tau tias arbitrary units.
Raws li txoj cai nyob rau hauv situ X-ray absorption qauv X-ray absorption qauv (XANES) spectra tau ua los kawm cov qauv hluav taws xob thiab geometric ntawm RuNi cov qauv nrog Ru foil thiab RuO2 cov qauv.Raws li qhia hauv daim duab.4c, raws li Ru loading txo, qhov kev siv ntawm cov kab dawb maj mam txo los ntawm Ru / Al2O3 cov qauv mus rau cov qauv RuNi.Lub caij no, qhov kev siv ntawm cov kab dawb ntawm XANES spectrum ntawm K-ntug ntawm Ni qhia tau hais tias nce me ntsis los ntawm tus qauv Ni qub mus rau cov qauv RuNi (Cov duab ntxiv 22).Qhov no qhia txog kev hloov pauv hauv electron ceev thiab kev sib koom ua ke ib puag ncig ntawm Ru tebchaw.Raws li pom nyob rau hauv lub X-ray photoelectron spectroscopy (XPS) spectra (Ntxiv daim duab 23), lub Ru0 ncov ntawm cov qauv RuNi hloov mus rau ib tug qis binding zog thiab lub Ni0 ncov hloov mus rau ib tug siab binding zog piv rau monometallic Ru thiab Ni., uas tseem qhia tau tias hloov hluav taws xob los ntawm Ni atoms rau Ru atoms hauv RuNi SAA.Lub Bader tus nqi tsom xam ntawm RuNi SAA (111) nto qhia tau hais tias cov Ru atoms cais tawm muaj cov nqi tsis zoo (Ruδ-) pauv los ntawm subsurface Ni atoms (Supplementary Fig. 24), uas yog raws li nyob rau hauv situ DRIFTS thiab XPS cov txiaj ntsig.Txhawm rau kawm txog cov qauv kev sib koom ua kom ntxaws ntawm Ru (Fig. 4d), peb tau ua tiav X-ray absorption fine-grained spectroscopy (EXAFS) hauv Fourier transform.Qauv muaj RuNi 0.4 wt.%. (Cov Lus Qhia Ntxiv 5 thiab Cov Duab Ntxiv 25–28) qhia tias txoj hauv kev Ru-Ni muaj tus lej sib koom tes (CN) ntawm 5.4, thaum tsis muaj Ru-Ru thiab Ru-O kev sib koom ua ke ntawm 0.4 wt.% RuNi qauv.Qhov no qhia tau hais tias lub ntsiab Ru atoms yog atomically dispersed thiab surrounded los ntawm Ni, ua ib tug monoatomic alloy.Nws yuav tsum raug sau tseg tias qhov siab tshaj plaws siv (~ 2.4 Å) ntawm Ru-Ru kev sib koom tes tshwm sim hauv cov qauv ntawm 0.6 wt.% RuNi thiab txhim kho hauv cov qauv los ntawm 2 wt.% RuNi.Tshwj xeeb, EXAFS nkhaus haum tau pom tias Ru-Ru kev sib koom tes tau nce ntau ntawm 0 (0.4 wt.% RuNi) mus rau 2.2 (0.6 wt.% RuNi) thiab ntxiv mus rau 6.7 (2 wt.% .% RuNi), feem. , qhia tias raws li Ru load nce, Ru atoms maj mam sib sau.K2-weighted wavelet transform (WT) ntawm Ru K-edge XAFS signals tau siv ntxiv los kawm txog kev sib koom tes ntawm Ru hom.Raws li qhia hauv daim duab.4e, Ru foil lobes ntawm 2.3 Å, 9.7 Å-1 xa mus rau Ru-Ru pab.Hauv cov qauv uas muaj RuNi 0.4 wt.%.Ru-Ni raug soj ntsuam ntawm 2.1 Å, 7.1 Å-1, uas ua pov thawj qhov tsim ntawm SAA.Tsis tas li ntawd, EXAFS spectra ntawm K-ntug ntawm Ni rau cov qauv sib txawv tsis muaj qhov sib txawv tseem ceeb (Cov duab ntxiv 29), qhia tias kev sib koom ua ke ntawm Ni yog tsis tshua muaj kev cuam tshuam los ntawm nto Ru atoms.Hauv luv luv, cov txiaj ntsig ntawm AC-HAADF-STEM, nyob rau hauv situ CO-DRIFTS, thiab nyob rau hauv situ XAFS thwmsim tau lees paub qhov kev npaj ua tiav ntawm RuNi SAA catalysts thiab evolution ntawm Ru hais ntawm Ni NPs los ntawm ib qho atoms mus rau Ru multimers los ntawm kev nce cov Ru load.Tsis tas li ntawd, cov duab HAADF-STEM (Sab Ntxiv Fig. 30) thiab EXAFS spectra (Supplementary Fig. 31) ntawm RuNi SAA catalysts siv tau pom tias lub xeev dispersion thiab kev sib koom ua ke ntawm Ru atoms tsis hloov pauv loj tom qab 5 lub voj voog, ua pov thawj. uas ruaj khov RuNi SAA catalyst .
Kev ntsuas H2-TPD tau ua los kawm txog qhov sib txawv adsorption ntawm hydrogen ntawm ntau cov catalysts thiab cov txiaj ntsig tau pom tias tag nrho cov catalysts muaj qhov muaj zog H2 dissociation muaj peev xwm nrog lub desorption ncov ntawm ~ 100 ° C (Supplementary Fig. 32).Cov txiaj ntsig ntawm kev txheeb xyuas kom muaj nuj nqis (Daim duab ntxiv 33) tsis tau qhia meej txog kev sib raug zoo ntawm cov reactivity thiab cov nyiaj ntawm hydrogen desorption.Tsis tas li ntawd, peb tau ua cov kev sim nrog D2 isotopes thiab tau txais cov txiaj ntsig kinetic isotope (KIE) tus nqi ntawm 1.31 (TOFH / TOFD) (Supplementary Fig. 34), qhia tias kev ua kom thiab kev sib cais ntawm H2 yog qhov tseem ceeb tab sis tsis txwv cov kauj ruam.Kev suav DFT tau ua los tshawb xyuas ntxiv txog qhov adsorption thiab dissociation tus cwj pwm ntawm hydrogen ntawm RuNi SAA piv rau metallic Ni ib leeg (Cov duab ntxiv 35).Rau RuNi SAA cov qauv, H2 molecules nyiam chemisorb tshaj ib qho Ru atoms nrog lub zog adsorption ntawm -0.76 eV.Tom qab ntawd, hydrogen dissociates rau hauv ob active H atoms ntawm lub hollow qhov chaw ntawm Ru-Ni RuNi SAA, kov yeej lub zog barrier ntawm 0.02 eV.Ntxiv rau qhov chaw Ru, H2 molecules kuj tuaj yeem raug chemisorbed rau ntawm qhov chaw sab saud ntawm Ni atoms uas nyob ib sab rau Ru (adsorption zog: -0.38 eV) thiab tom qab ntawd dissociated rau ob Hs ntawm Ru-Ni thiab Ni-Ni hollow sites.Atomic barrier 0.06 eV.Ntawm qhov tsis sib xws, lub zog teeb meem rau kev nqus thiab sib cais ntawm H2 molecules ntawm Ni (111) nto yog -0.40 eV thiab 0.09 eV, raws li.Lub zog tsis tshua muaj zog thiab qhov sib txawv tsis tseem ceeb qhia tau hais tias H2 yooj yim dissociates ntawm Ni thiab RuNi surfactants (Ni-site lossis Ru-site), uas tsis yog qhov tseem ceeb cuam tshuam rau nws cov kev ua haujlwm catalytic.
Activated adsorption ntawm qee pawg ua haujlwm yog qhov tseem ceeb rau kev xaiv hydrogenation ntawm substrates.Yog li ntawd, peb tau ua DFT xam los soj ntsuam cov configurations muaj peev xwm ntawm 4-NS adsorption thiab active sites ntawm lub RuNi SAA(111) nto, thiab optimization tau tshwm sim nyob rau hauv Ntxiv Fig. 36. Seemingly parallel configuration (Fig. 5a thiab Supplementary Fig. 36e), nyob rau hauv uas N atoms nyob rau hauv Ru-Ni hollow qhov chaw thiab ob O atoms yog sib koom ua ke rau Ru-Ni interface qhia tau hais tias lub zog adsorption qis tshaj (-3.14 eV).Qhov no qhia tau hais tias lub thermodynamically zoo dua adsorption regime piv rau ntsug thiab lwm yam parallel configurations (Ntxiv Fig. 36a–d).Tsis tas li ntawd, tom qab adsorption ntawm 4-HC ntawm RuNi SAA (111), qhov ntev ntawm N-O1 (L(N-O1)) daim ntawv cog lus hauv pawg nitro tau nce mus rau 1.330 Å (Fig. 5a), uas yog ntau heev. ntev tshaj qhov ntev ntawm lub gaseous 4- NS (1.244 Å) (Supplementary Fig. 37), txawm tshaj L (N-O1) (1.315 Å) ntawm Ni (111).Qhov no qhia tau hais tias cov activated adsorption ntawm N-O1 daim ntawv cog lus nyob rau saum npoo ntawm RuNi PAA yog ho txhim khu kev qha piv rau thawj Ni (111).
Adsorption configurations ntawm 4-HC ntawm Ni(111) thiab RuNi SAA(111) (Eads) nto (sab thiab sab saum toj views).Ru - violet, Ni - ntsuab, C - txiv kab ntxwv, O - liab, N - xiav, H - dawb.b Nyob rau hauv situ FT-IR spectra ntawm gaseous thiab chemisorbed 4-HC ntawm monometallic surfactants Ni, Ru, RuNi (0.4 wt. %) thiab 2 wt.% RuNi, raws.c Normalized nyob rau hauv situ XANES thiab d-theem-kho Fourier EXAFS ntawm Ru K-ntug ntawm 0.4 wt % RuNi PAA thaum lub sij hawm 4-NS adsorption (RuNi SAA–4NS) thiab cov kauj ruam hydrogenation (RuNi SAA–4NS–H2). ;…e Projection density of states (PDOS) of the first surface of RuNi SAA(111), N-O1 in gaseous 4-NS and adsorbed 4-NS on RuNi SAA(111)."au" txhais tau tias arbitrary units.
Txhawm rau kuaj ntxiv tus cwj pwm adsorption ntawm 4-NS, nyob rau hauv qhov chaw FT-IR ntsuas tau ua rau Ni monometallic, Ru monometallic, 0.4 wt% RuNi (SAA), thiab 2 wt% RuNi catalysts (Fig. 5b).FT-IR spectrum ntawm gaseous 4-NS nthuav tawm peb tus yam ntxwv ncov ntawm 1603, 1528, thiab 1356 cm–1, uas tau muab rau ν(C = C), νas (NO2), thiab νs (NO2) 46,47, 48.Nyob rau hauv lub xub ntiag ntawm monometallic Ni, redshifts ntawm tag nrho peb pawg yog pom: v (C = C) (1595 cm–1), νas (NO2) (1520 cm–1), thiab νs (NO2) (1351 cm–1) ., uas qhia txog chemisorption ntawm C = C thiab -NO2 pawg ntawm Ni nto (feem ntau yuav, nyob rau hauv configuration ntawm parallel adsorption).Rau ib qho piv txwv ntawm monometallic Ru, redshifts ntawm peb bands (1591, 1514, thiab 1348 cm-1, raws li) txheeb ze rau monometallic Ni tau pom, uas qhia tau hais tias ib tug me ntsis enhanced adsorption ntawm nitro pawg thiab С = С bonds ntawm Ru.Nyob rau hauv cov ntaub ntawv ntawm 0.4 wt.% RuNi (SAA), lub ν(C = C) band yog nyob nruab nrab ntawm 1596 cm–1, uas yog heev ze rau lub monometallic Ni band (1595 cm–1), qhia tau hais tias cov vinyl pawg nyiam adsorb Ni ntawm lub RuNi SAA sites.Tsis tas li ntawd, nyob rau hauv sib piv rau cov monometallic catalyst, cov txheeb ze siv ntawm νs (NO2) band (1347 cm-1) yog ntau weaker tshaj lub νas (NO2) band (1512 cm-1) ntawm 0.4 wt.% RuNi (SAA. ), uas tau cuam tshuam nrog cleavage ntawm NO daim ntawv cog lus rau -NO2 los ua ib tug nitroso intermediate raws li yav dhau los kev tshawb fawb 49,50.Ib qho tshwm sim zoo sib xws kuj tau pom hauv cov qauv nrog cov ntsiab lus RuNi ntawm 2 wt.%.Cov txiaj ntsig saum toj no tau lees paub tias qhov kev sib koom ua ke ntawm cov chaw bimetallic hauv PAA RuNi txhawb cov polarization thiab dissociation ntawm nitro pawg, uas yog pom zoo nrog rau qhov zoo tshaj plaws adsorption configuration tau los ntawm DFT xam.
Hauv qhov chaw XAFS spectroscopy tau ua los kawm txog kev hloov pauv hloov pauv ntawm cov qauv hluav taws xob thiab kev sib koom ua haujlwm ntawm RuNi SAA thaum lub sijhawm 4-NS adsorption thiab cov tshuaj tiv thaiv catalytic.Raws li pom tau los ntawm K-edge XANES spectrum ntawm Ru (Fig. 5c), tom qab adsorption ntawm 4-HC, 0.4 wt.% RuNi PAA, lub nqus nqus tau hloov pauv mus rau lub zog siab dua, uas yog nrog los ntawm kev nce siab ntawm cov kab dawb, uas qhia tias Ru hom Ib nrab oxidation tshwm sim vim kev hloov hluav taws xob los ntawm Ru mus rau 4-NS.Tsis tas li ntawd, cov theem kho Fourier hloov EXAFS spectrum ntawm adsorbed 4-NS RuNi SAA (Fig. 5d) qhia tau hais tias qhov kev txhim kho ntawm cov teeb liab ntawm ~ 1.7 Å thiab ~ 3.2 Å, uas yog txuam nrog kev tsim ntawm Ru-O kev sib koom tes.XANES thiab EXAFS spectra ntawm 0.4 wt% RuNi SAA rov qab mus rau lawv lub xeev qub tom qab 30 feeb txhaj tshuaj hydrogen.Cov xwm txheej no qhia tau hais tias cov pab pawg nitro tau adsorbed ntawm Ru chaw ntawm Ru-O daim ntawv cog lus raws li kev sib cuam tshuam hauv hluav taws xob.Raws li rau XAFS spectra ntawm Ni-K ntug nyob rau hauv situ (Suab ntxiv Fig. 38), tsis pom muaj kev hloov pauv, uas tej zaum yuav yog vim cov nyhuv ntawm dilution ntawm Ni atoms nyob rau hauv tej theem ntawm nto Ni hais.Qhov kev kwv yees ceev ntawm cov xeev (PDOS) ntawm RuNi SAA (Fig. 5e) qhia tau hais tias lub xeev unoccupied ntawm nitro pawg saum toj no Femi theem broadens thiab txav hauv qab Femi theem nyob rau hauv lub adsorbed lub xeev, uas kuj qhia tau hais tias electrons los ntawm lub d- Lub xeev ntawm RuNi SAA hloov mus rau lub xeev tsis muaj neeg nyob hauv −NO2.Tus nqi sib txawv ntawm qhov sib txawv (Ntxiv daim duab 39) thiab Bader tus nqi tsom xam (Ntxiv daim duab 40) qhia tau hais tias kev sib xyaw electron ceev ntawm 4-NS accumulates tom qab nws adsorption ntawm qhov chaw ntawm RuNi SAA (111).Tsis tas li ntawd, -NO2 tus nqi them ceev tau nce ntau dua piv rau cov vinyl pawg hauv 4-NS vim kev hloov hluav taws xob ntawm Ru-Ni interface, qhia tshwj xeeb ua kom tsis muaj nyiaj hauv pawg nitro.
Hauv qhov chaw FT-IR tau ua los saib xyuas cov txheej txheem catalytic ntawm 4-NS hydrogenation cov tshuaj tiv thaiv ntawm cov qauv catalyst (Fig. 6).Rau qhov pib nickel catalyst (Fig. 6a), tsuas yog txo qis me ntsis ntawm qhov ceev ntawm nitro (1520 thiab 1351 cm-1) thiab C = C (1595 cm-1) bands tau pom thaum dhau H2 rau 12 min, uas qhia tias - Ua kom NO2 thiab C = C tsis muaj zog.Nyob rau hauv lub xub ntiag ntawm monometallic Ru (Fig. 6b), lub ν(C = C) band (ntawm 1591 cm–1) ceev nrooj nyob rau hauv 0-12 min, thaum lub νs (NO2) thiab νas (NO2) bands yog heev txo. .Slow Qhov no qhia tau hais tias qhov kev nyiam tshaj plaws ntawm pawg vinyl rau hydrogenation, ua rau kev tsim ntawm 4-nitroethylbenzene (4-NE).Nyob rau hauv cov ntaub ntawv ntawm 0.4 wt.% RuNi (SAA) (Fig. 6c), lub νs(NO2) band (1347 cm–1) sai sai disappears nrog influx ntawm hydrogen, nrog rau ib tug maj mam lwj ntawm ν(N = O);Ib pawg tshiab nyob nruab nrab ntawm 1629 cm-1 kuj tau pom, raug ntaus nqi rau kev sib tsoo ntawm NH.Tsis tas li ntawd, cov qhab rau ν(C = C) (1596 cm–1) qhia tau tias tsuas yog txo qis me ntsis tom qab 12 min.Qhov kev hloov pauv hloov pauv no lees paub qhov polarization thiab hydrogenation ntawm -NO2 rau -NH2 los ntawm 0.4 wt% RuNi (SAA) raws li qhov tshwj xeeb chemoselectivity ntawm 4-aminostyrene.Rau ib qho piv txwv ntawm 2 wt.% RuNi (Fig. 6d), ntxiv rau qhov pom ntawm ib pawg tshiab ntawm 1628 cm–1 ntaus nqi rau δ(NH), ν(C = C) band feem ntau txo qis thiab ploj mus nrog nce band ntawm nitro pawg (1514 thiab 1348 cm–1).Qhov no qhia tau hais tias C = C thiab -NO2 tau txais txiaj ntsig zoo vim muaj Ru-Ru thiab Ru-Ni interfacial chaw nruab nrab, feem, uas sib haum rau kev tsim ntawm 4-NE thiab 4-AE ntawm 2 wt.% RuNi catalyst.
Nyob rau hauv situ FT-IR spectra ntawm 4-NS hydrogenation nyob rau hauv lub xub ntiag ntawm monometallic Ni, b monometallic Ru, c 0.4 wt% RuNi SAA, thiab d 2 wt% RuNi nyob rau hauv H2 ntws ntawm 1700-1240 cm- Range 1 raug kaw raws li lub cov tshuaj tiv thaiv roj tom qab 0, 3, 6, 9 thiab 12 feeb, feem."au" txhais tau tias arbitrary units.Muaj peev xwm faib hluav taws xob thiab cov qauv zoo sib xws rau C = C hydrogenation thiab tsis muaj kev sib tsoo rau hauv 4-NS ntawm e Ni(111) thiab f RuNi SAA(111) nto.Ru - violet, Ni - ntsuab, C - txiv kab ntxwv, O - liab, N - xiav, H - dawb.“ads”, “IS”, “TS”, thiab “FS” sawv cev rau lub xeev adsorption, lub xeev pib, lub xeev hloov, thiab lub xeev kawg, feem.
Txoj hauv kev muaj peev xwm rau 4-NS kev hloov pauv mus rau Ni(111) thiab RuNi SAA(111), suav nrog C = C hydrogenation thiab NO daim ntawv cog lus cleavage, tau tshawb xyuas los ntawm DFT xam ntxiv kom paub meej lub luag haujlwm tseem ceeb ntawm 4-NS.Tshooj ntawm Ru-Ni interface rau kev tsim cov 4-AS lub hom phiaj.Rau Ni(111) nto (Fig. 6e), lub zog teeb meem rau NO scission thiab hydrogenation ntawm vinyl pawg nyob rau hauv thawj theem yog 0.74 thiab 0.72 eV, feem, uas qhia tau hais tias cov chemoselective hydrogenation ntawm nitro pawg nyob rau hauv 4-HC yog tsis zoo.rau monometallic nickel nto.Ntawm qhov tsis sib xws, lub zog thaiv kev tsis sib haum xeeb tsuas yog 0.46 eV siab dua li ntawm RuNi SAA (111), uas yog qis dua li ntawm C = C bond hydrogenation (0.76 eV) (Fig. 6f).Qhov no unambiguously lees paub tias lub Ru-Ni interfacial chaw ua tau zoo txo ​​lub zog barrier rau NO scission nyob rau hauv nitro pawg, ua rau ib tug thermodynamically nyiam txo cov nitro pawg piv rau C = C pawg nyob rau hauv lub RuNi surfactant nto, uas pom zoo nrog rau cov kev sim.
Cov tshuaj tiv thaiv mechanism thiab xam lub zog nkhaus ntawm 4-NS hydrogenation ntawm RuNi SAA tau tshawb xyuas raws li DFT suav (Fig. 7), thiab cov ncauj lus kom ntxaws adsorption configuration ntawm cov kauj ruam tseem ceeb yog qhia nyob rau hauv Supplementary Fig. 41. Kom optimize qhov kev pab cuam xam, lub zog-ua teeb meem rau cov dej molecules raug tshem tawm los ntawm kev suav.phaj qauv 9,17.Raws li qhia hauv daim duab.7, 4-NS molecules yog thawj absorbed nyob rau hauv parallel ntawm lub RuNi surfactant, thiab ob lub O atoms nyob rau hauv lub nitro pab pawg neeg yog khi rau lub Ru-Ni interfacial chaw (S0; kauj ruam I).Tom qab ntawd, NO daim ntawv cog lus txuas nrog rau qhov chaw Ru yog tawg, uas yog nrog los ntawm kev tsim ntawm nitroso intermediate (C8H7NO *) ntawm Ru-Ni interface site thiab O* ntawm qhov khoob Ni site (S0 → S1 ntawm TS1; lub zog. barrier: 0.46 eV, kauj ruam thib ob).O * radicals yog hydrogenated los ntawm active H atoms los ua H2O molecules nrog ib tug exotherm ntawm 0.99 eV (S1 → S2).Lub zog teeb meem rau hydrogenation ntawm C8H7NO * nruab nrab (Cov duab ntxiv 42 thiab 43) qhia tias reactive H atoms los ntawm hollow Ru-Ni qhov chaw nyiam tawm tsam O atoms tshaj N atoms, ua rau C8H7NOH * (S2 → S4; lub zog barrier TS2: 0.8). eV, Step III).Cov N atoms hauv C8H7NOH * ces hydrogenated los ua C8H7NHOH * tom qab hla 1.03 eV barrier (S4 → S6; kauj ruam IV), uas yog lub ntsiab lus ntawm tag nrho cov tshuaj tiv thaiv.Tom ntej no, N-OH daim ntawv cog lus hauv C8H7NHOH * tau tawg ntawm Ru-Ni interface (S6 → S7; lub zog barrier: 0.59 eV; theem V), tom qab uas OH * tau hydrogenated rau HO (S7 → S8; exotherm: 0.31 eV Tom qab ntawd, N atoms ntawm Ru-Ni hollow qhov chaw hauv C8H7NH * tau ntxiv hydrogenated los ua C8H7NH2 * (4-AS) nrog lub zog thaiv ntawm 0.69 eV (S8 → S10; kauj ruam VI).Thaum kawg, 4-AS thiab HO molecules tau desorbed los ntawm RuNi-PAA nto, thiab cov catalyst rov qab mus rau nws lub xeev qub (qib VII).Qhov tshwj xeeb interfacial qauv ntawm ib leeg Ru atoms thiab Ni substrates, nrog rau kev sib koom ua ke ntawm tus tswv tsev doping hauv RuNi SAA, ua rau muaj kev ua haujlwm zoo thiab chemoselectivity ntawm 4-NS hydrogenation.
Rice.4. Schematic daim duab ntawm lub mechanism ntawm hydrogenation cov tshuaj tiv thaiv ntawm NS rau 4-AS ntawm RuNi PAA nto.Ru - violet, Ni - ntsuab, C - txiv kab ntxwv, O - liab, N - xiav, H - dawb.Lub inset qhia txog kev faib tawm lub peev xwm ntawm 4-NS hydrogenation ntawm RuNi SAA (111) nto, xam raws li DFT."S0" sawv cev rau lub xeev thawj zaug, thiab "S1-S10" sawv cev rau ntau lub xeev adsorption."TS" sawv cev rau lub xeev kev hloov pauv.Cov lej hauv cov kab ke sawv cev rau lub zog teeb meem ntawm cov kauj ruam tseem ceeb, thiab cov lej seem sawv cev rau lub zog adsorption ntawm cov khoom nruab nrab uas sib raug.
Yog li, RuNi SAA catalysts tau txais los ntawm kev siv cov tshuaj electrosubstitution ntawm RuCl3 thiab Ni NPs tau los ntawm LDH precursors.Piv nrog rau yav dhau los qhia monometallic Ru, Ni thiab lwm yam heterogeneous catalysts, qhov tshwm sim RuNi SAA pom superior catalytic efficiency rau 4-NS chemoselective hydrogenation (4-AS yield: > 99%; TOF tus nqi: 4293 h-1).Kev sib xyaw ua ke nrog rau AC-HAADF-STEM, nyob rau hauv qhov chaw CO-DRIFTS, thiab XAFS tau lees paub tias Ru atoms tau immobilized ntawm Ni NPs ntawm ib-atom theem ntawm Ru-Ni daim ntawv cog lus, uas tau nrog electron hloov ntawm Ni mus rau Ru.Nyob rau hauv situ XAFS, FT-IR thwmsim, thiab DFT xam pom tau hais tias lub Ru-Ni interface site ua hauj lwm pab raws li ib tug sab hauv active site rau nyiam ua kom tsis muaj daim ntawv cog lus nyob rau hauv lub nitro pawg;synergism ntawm Ru thiab cov chaw nyob sib ze Ni pab txhawb kev ua haujlwm nruab nrab thiab hydrogenation, yog li txhim kho catalytic efficiency.Txoj haujlwm no muab kev nkag siab txog kev sib raug zoo ntawm cov chaw ua haujlwm bifunctional thiab tus cwj pwm catalytic ntawm SAA ntawm qib atomic, paving txoj hauv kev rau kev tsim qauv tsim nyog ntawm lwm cov catalysts uas xav tau xaiv.
Cov tshuaj analytical reagents siv hauv qhov kev sim tau yuav los ntawm Sigma Aldrich: Al2(SO4)3 18H2O, sodium tartrate, CO(NH2)2, NH4NO3, Ni(NO3)2 6H2O, RuCl3, ethanol, 4-nitrostyrene (4- NS) , 4-aminoostyrene, 4-nitroethylbenzene, 4-aminoethylbenzene thiab nitrostyrene.Cov dej huv huv tau siv hauv txhua qhov kev sim.
Hierarchical NiAl LDHs tau tsim los ua cov neeg ua ntej los ntawm kev loj hlob hauv qhov chaw.Ua ntej, urea (3.36 g), Al2 (SO4) 3 · 18H2O (9.33 g) thiab sodium tartrate (0.32 g) tau yaj hauv dej deionized (140 ml).Cov txiaj ntsig tau raug xa mus rau Teflon-coated autoclave thiab rhuab mus rau 170 ° C rau 3 teev.Lub resulting precipitate tau ntxuav nrog dej distilled thiab kom qhuav, tom qab ntawd nws yog calcined ntawm 500 ° C (2 ° C min-1; 4 h) kom tau txais amorphous Al2O3 .Tom qab ntawd Al2O3 (0.2 g), Ni (NO3) 2 6H2O (5.8 g) thiab NH4NO3 (9.6 g) tau tawg rau hauv dej huv (200 ml) thiab pH raug hloov mus rau ~ 6.5 los ntawm kev ntxiv 1 mol l -1 ammonia dej..Qhov kev ncua raug xa mus rau hauv lub khob thiab khaws cia ntawm 90 ° C rau 48 teev kom tau txais NiAl-LDH.Tom qab ntawd NiAl-LDH hmoov (0.3 g) raug txo nyob rau hauv ib tug kwj ntawm H2 / N2 (10/90, v / v; 35 ml min-1) ntawm 500 ° C rau 4 h (kub tus nqi: 2 ° C min -1 ).Kev npaj cov qauv ntawm monometallic npib tsib xee (Ni / Al2O3) tso rau ntawm amorphous Al2O3.Cov qauv tso nyiaj bimetallic ntawm RuNi tau tsim los ntawm txoj kev electrodisplacement.Feem ntau, cov qauv tshiab ntawm Ni / Al2O3 (0.2 g) tau tawg nyob rau hauv 30 ml ntawm dej ntshiab, tom qab ntawd ib qho kev daws ntawm RuCl3 (0.07 mmol l-1) tau ntxiv maj mam thiab nplawm rau 60 feeb nyob rau hauv kev tiv thaiv ntawm N2 huab cua. .Lub resulting precipitate yog centrifuged, ntxuav nrog dej ntshiab, thiab qhuav nyob rau hauv lub tshuab nqus tsev qhov cub ntawm 50 ° C rau 24 teev, tau txais ib tug qauv uas muaj 0.1% RuNi.Ua ntej qhov kev ntsuam xyuas catalytic, cov qauv tshiab tau tsim ua ntej raug txo qis hauv H2 / N2 ntws (10/90, v / v) ntawm 300 ° C (rhaub cua sov: 2 ° C min-1) rau 1 h, thiab tom qab ntawd rhaub hauv N2 Txias rau chav sov.Rau kev siv: cov qauv nrog Ru / Al2O3 cov ntsiab lus ntawm 0.4% thiab 2% los ntawm huab hwm coj, nrog cov ntsiab lus Ru tseeb ntawm 0.36% los ntawm huab hwm coj thiab 2.3% los ntawm huab hwm coj, tau npaj los ntawm nag los nag thiab cua sov ntawm 300 ° C (siv H2 / N2: 10/90, v / v, cua sov: 2 ° C min-1) rau 3 teev.
X-ray diffraction (XRD) kev sim tau ua tiav ntawm Bruker DAVINCI D8 ADVANCE diffractometer nrog Cu Kα hluav taws xob qhov chaw (40 kV thiab 40 mA).Lub Shimadzu ICPS-7500 Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) tau siv los txiav txim siab qhov muaj ntau ntawm cov ntsiab lus hauv ntau cov qauv.Cov duab scanning electron microscopy (SEM) dluab tau siv lub Zeiss Supra 55 electron microscope.N2 adsorption-desorption thwmsim tau ua tiav ntawm Micromeritics ASAP 2020 ntaus ntawv thiab thaj chaw tshwj xeeb tau suav nrog siv Brunauer-Emmett-Teller (BET) multipoint method.Cov yam ntxwv kis tau tus mob electron microscopy (TEM) tau ua tiav ntawm JEOL JEM-2010 high-resolution kis electron microscope.High Angle Aberration Corrected Scanning Transmission Electron Microscope Dark Field (AC-HAADF) - STEM nrog FEI Titan Cube Themis G2 300 nrog spherical aberration corrector thiab Energy Dispersive X-ray Spectroscopy (EDS) system thiab JEOL JEM-ARM200F ntsuas) thiab EDS mapping ntsuas .Cov qauv zoo X-ray absorption spectroscopy (XAFS) nyob rau hauv situ K-ntug ntawm Ru thiab Ni K-edge tau ntsuas ntawm raws 1W1B thiab 1W2B ntawm Beijing Synchrotron Radiation Facility (BSRF) ntawm Lub Tsev Haujlwm ntawm Lub Zog Zog Physics (IHEP), Tuam Tshoj .Academy ntawm Sciences (KAN).Pulsed CO chemisorption thiab kub-programmed hydrogen desorption (H2-TPD) thwmsim tau ua nyob rau ntawm Micromeritics Autochem II 2920 ntsuas siv lub thermal conductivity detector (TCD).Cov kev sim hauv situ DRIFTS thiab FT-IR tau ua tiav ntawm Bruker TENSOR II infrared spectrometer nruab nrog kev hloov kho hauv situ cov tshuaj tiv thaiv cell thiab lub ntsuas MCT siab heev.Cov txheej txheem qhia tus cwj pwm kom ntxaws tau piav qhia hauv Cov Lus Qhia Ntxiv.
Ua ntej, lub substrate (4-NS, 1 mmol), hnyav (ethanol, 8 ml) thiab catalyst (0.02 g) tau ua tib zoo ntxiv rau 25 ml stainless hlau autoclave.Tom qab ntawd lub reactor tau purged tag nrho nrog 2.0 MPa (> 99.999%) hydrogen 5 zaug, thiab ces nias thiab kaw rau 1.0 MPa nrog H2.Cov tshuaj tiv thaiv tau ua tiav ntawm 60 ° C ntawm qhov sib txuas tas li ntawm 700 rpm.Tom qab cov tshuaj tiv thaiv, cov khoom tsim tau raug txheeb xyuas los ntawm GC-MS thiab txheeb xyuas ntau yam siv Shimadzu GC-2014C gas chromatography system nruab nrog GSBP-INOWAX capillary kem (30 m × 0.25 mm × 0.25 mm) thiab FID detector.Kev hloov pauv 4-nitrostyrene thiab cov khoom xaiv tau txiav txim siab raws li hauv qab no:
Turnover zaus (TOF) qhov tseem ceeb tau xam raws li mol 4-NS hloov dua siab tshiab rau ib mol hlau qhov chaw ib teev (mol4-NS mol-1 h-1) raws li qis 4-NS conversion (~15%).Raws li tus naj npawb ntawm Ru nodes, Ru-Ni interface nodes thiab tag nrho cov naj npawb ntawm cov hlau atoms.Rau qhov kev xeem rov ua dua tshiab, cov catalyst tau sau los ntawm centrifugation tom qab cov tshuaj tiv thaiv, ntxuav peb zaug nrog ethanol, thiab tom qab ntawd rov muab tso rau hauv autoclave rau lub voj voog catalytic tom ntej.
Txhua qhov kev ua haujlwm ceev ceev (DFT) suav nrog siv Vienna ab initio simulation pob (VASP 5.4.1).Generalized Gradient Approximation (GGA) PBE muaj nuj nqi yog siv los piav qhia txog kev sib pauv hluav taws xob thiab kev sib raug zoo.Txoj kev Projector Augmented Wave (PAW) yog siv los piav txog kev sib cuam tshuam ntawm atomic nuclei thiab electrons.Txoj kev Grimm DFT-D3 piav qhia txog cov txiaj ntsig ntawm van der Waals kev sib cuam tshuam ntawm cov substrate thiab qhov cuam tshuam.Kev suav ntawm Lub Zog Teeb Meem los ntawm Kev Sib Tw Elastic Bands nrog Duab Boost (CI-NEB) thiab Dimer Methods.Kev soj ntsuam zaus ntawm cov oscillations tau ua tiav, lees paub tias muaj tsuas yog ib qho kev xav ntau zaus hauv txhua lub xeev hloov pauv (Cov duab ntxiv 44–51).Cov lus qhia ntxaws ntxiv tau piav qhia hauv cov ntaub ntawv ntxiv.
Cov ntaub ntawv tseem ceeb uas txhawb cov phiaj xwm hauv kab lus no yog muab rau hauv cov ntaub ntawv cov ntaub ntawv.Lwm cov ntaub ntawv ntsig txog txoj kev tshawb fawb no muaj los ntawm cov kws sau ntawv raws li qhov kev thov tsim nyog.Kab lus no muab cov ntaub ntawv qub.
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