title: Do Ni/Cu and Cu/Ni alloys have different catalytic performances towards water-gas shift? A density functional theory investigation.
abstract: Density functional calculations were preformed to investigate whether adding Ni into a Cu surface (denoted as Cu/Ni) or adding Cu into a Ni surface (Ni/Cu) is more efficient for catalyzing the water-gas shift (WGS)? The reactions of water dissociation and monoxide dissociation were selected to assess the activity and selectivity towards WGS, respectively. Our results show that Ni-atom modification of surfaces is thermodynamically favorable for both reactions. Kinetically, compared with pure Cu, water dissociation is greatly facilitated on Ni-modified surfaces, and the activity is insensitive to the Ni concentration; however, monoxide dissociation is not well-promoted on one Ni-atom-modified surfaces, but two Ni-atom modification can notably decrease the dissociation barriers. Overall, on the basis of these results, we conclude that 1) the catalytic performance of bimetallic metals is superior to monometallic ones; 2) at the same Ni concentration on the surface, Cu/Ni and Ni/Cu alloys have almost the same performance towards WGS; and 3) to acquire high WGS performance, the surface Ni atoms should either be low in concentration or highly dispersed.
authors.affiliation: Center for Nano Science and Technology, College of Chemistry and Material Science, The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, Anhui Normal University, Beijing east Road 1, Wuhu (PR China). dujinyn@mail.ahnu.edu.cn.
authors.forename: Yu Cheng
authors.initials: YC
authors.lastname: Huang
authors.forename: Tao
authors.initials: T
authors.lastname: Zhou
authors.forename: Hai
authors.initials: H
authors.lastname: Liu
authors.forename: ChongYi
authors.initials: C
authors.lastname: Ling
authors.forename: SuFan
authors.initials: S
authors.lastname: Wang
authors.forename: Jin Yan
authors.initials: JY
authors.lastname: Du
keywords: alloys; copper; density functional calculations; nickel; water-gas shift