期刊
CATALYSTS
卷 12, 期 11, 页码 -出版社
MDPI
DOI: 10.3390/catal12111380
关键词
alloy; cobalt; coking; DFT; hydrogenation; intermetallic; nickel
资金
- FONDECYT [1170610, ANID BECAS/DOCTORADO NACIONAL 2018/21180468, ANID BECAS/DOCTORADO NACIONAL 2021/21210586]
- supercomputing infrastructure of the NLHPC [ECM-02]
- Conicyt Programa de Astronomia Fondo Quimal [2017 QUIMAL170001]
- Conicyt [PIA ACT172033]
- Fondecyt Iniciacion [11170268]
- National Science Foundation [2034911, TG-CTS150005]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [2034911] Funding Source: National Science Foundation
This study investigates the impact of surface carbon deposits on Ni and Co catalysts, and finds that bimetallic NiCo catalysts exhibit better stability in CO hydrogenation reactions.
Surface carbon deposits deactivate Ni and Co catalysts in reactions involving hydrocarbons and COx. Electronic properties, adsorption energies of H, C, and CHx species, and the energetics of the hydrogenation of surface C atom to methane are studied for (100) and (111) surfaces of monometallic Ni and Co, and bimetallic NiCo. The bimetallic catalyst exhibits a Co -> Ni electron donation and a concomitant increase in the magnetization of Co atoms. The CHx species resulting from sequential hydrogenation are more stable on Co than on Ni atoms of the NiCo surfaces due to more favorable (C-H)-Co agostic interactions. These interactions and differences between Co and Ni sites are more significant for (111) than for (100) bimetallic surfaces. On (111) surfaces, CH is the most stable species, and the first hydrogenation of C atom exhibits the highest barrier, followed by the CH3 hydrogenation steps. In contrast, on (100) surfaces, surface C atom is the most stable species and CH2 or *CH3 hydrogenations exhibit the highest barriers. The Gibbs free energy profiles suggest that C removal on (111) surfaces is thermodynamically favorable and exhibits a lower barrier than on the (100) surfaces. Thus, the (100) surfaces, especially Ni(100), are more prone to C poisoning. The NiCo(100) surfaces exhibit weaker binding of C and CHx species than Ni(100) and Co(100), which improves C poisoning resistance and lowers hydrogenation barriers. These results show that the electronic effects of alloying Ni and Co strongly depend on the local site composition and geometry.
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