Catalytic Reactivity of CuNi Alloys toward H2O and CO Dissociation for an Efficient Water鈥揋as Shift: A DFT Study

详细信息    查看全文

• 作者：Li-Yong Gan ; Ren-Yu Tian ; Xiao-Bao Yang ; Hong-Duo Lu ; Yu-Jun Zhao
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：January 12, 2012
• 年：2012
• 卷：116
• 期：1
• 页码：745-752
• 全文大小：487K
• 年卷期：v.116,no.1(January 12, 2012)
• ISSN：1932-7455

文摘

Density functional theory (DFT) calculations are employed to study H₂O and CO dissociations on a set of CuNi bimetallic surfaces aiming at exploring the optimal Ni ensemble on Cu(111) for an efficient water鈥揼as shift (WGS) process, i.e., splitting H₂O with high reactivity and avoiding CO activation. We found that Ni additives in the Cu(111) surface layer including a Ni monomer can remarkably enhance water splitting. Meanwhile, H₂O dissociation barriers (E_act) are strongly correlated with the H adsorption energies (E_ad): the larger E_ad, the smaller E_act. Moreover, H₂O dissociation may be more practical via the dissociated H* rather than OH closing to Ni atoms. For the scission of the C鈥揙 bond, the process is unfavorable on Ni monomers, though it is obviously promoted on Ni dimers, trimers, and other ensembles with higher Ni content. It is deduced that the selectivity of the Cu鈥揘i bimetallic catalysts toward WGS would decrease with increasing Ni concentration. These findings suggest that the bimetallic CuNi catalysts with highly dispersed Ni ensembles containing lower Ni concentration should exhibit high performance for the WGS process.