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

Density functional theory (DFT) calculations are employed to study H 2 O and CO dissociations on a set of CuNi bimetallic surfaces aiming at exploring the optimal Ni ensemble on Cu(111) for an efficient water–gas shift (WGS) process, i.e., splitting H 2 O 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, H 2 O dissociation barriers ( E act ) are strongly correlated with the H adsorption energies ( E ad ): the larger E ad, the smaller E act . Moreover, H 2 O dissociation may be more practical via the dissociated H* rather than OH closing to Ni atoms. For the scission of the C–O 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–Ni 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.