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Reaction mechanism and selectivity of acetylene hydrogenation over Ni-Ga intermetallic compound catalysts: a density functional theory study

Abstract

Intermetallic compounds (IMCs) have shown excellent catalytic performance toward selective hydrogenation of acetylene, but the theoretical understanding on this reaction over Ni-based IMCs is rather limited. In this work, the adsorptions of the C2 species, Bader charge, projected density of states (PDOS) and the reaction pathways were calculated by density functional theory (DFT) method to investigate the mechanism and selectivity for the acetylene hydrogenation on (111) surface of NinGa (n=1,3) IMCs, with the comparative study on pristine Ni(111) surface. The results indicate that the adsorption energy of acetylene increased along with the Ni/Ga ratio, therefore a feasible acetylene adsorption on Ga-rich surface guaranteed a low effective barrier, leading the best activity for the NiGa(111) surface among three surfaces. Bader charge analysis show that electrons transferred from Ga atoms to Ni atoms and further delivered to C2 species, decreasing the adsorption capacity of C2 species on NiGa(111) in comparison with those on Ni(111) and Ni3Ga(111). The reaction pathway of acetylene hydrogenation to ethylene via vinyl or even over-hydrogenation to ethane via ethyl is more favorable than the pathway involving ethylidene intermediate on all surfaces. Moreover, the ethylene selectivity has a positive correlation with the gallium content by comparing the desorption barrier with the hydrogenation barrier of ethylene, thus NiGa(111) surface also exhibits the best selectivity. Therefore, NiGa(111) surface demonstrates to be an excellent reaction facet for the semihydrogenation of acetylene, which agreed with the experimental findings, and would provide helpful instructions for designing and preparing highly-selective and noble-substitute catalysts of alkyne semihydrogenation.

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Publication details

The article was received on 14 Dec 2017, accepted on 05 Feb 2018 and first published on 06 Feb 2018


Article type: Paper
DOI: 10.1039/C7DT04726F
Citation: Dalton Trans., 2018, Accepted Manuscript
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    Reaction mechanism and selectivity of acetylene hydrogenation over Ni-Ga intermetallic compound catalysts: a density functional theory study

    D. Rao, S. T. Zhang, C. Li, Y. Chen, M. Pu, H. Yan and M. Wei, Dalton Trans., 2018, Accepted Manuscript , DOI: 10.1039/C7DT04726F

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