Enhanced Selectivity to H2 Formation in Decomposition of HCOOH on the Ag19@Pd60 Core-Shell Nanocluster from First-Principles

In this study, using spin-polarized density functional theory calculation we examined the origin of enhanced catalytic activity toward H-2 production from HCOOH in Ag-19@Pd-60 core shell nanoclusters (a 79-atom truncated octahedral cluster models). First, we find that the Pd monolayer shell on the Ag core can greatly enhance the selectivity to H-2 formation via HCOOH decomposition compared to the pure Pd-79 cluster by substantially reducing the binding energy of key intermediate HCOO and in turn the barrier for dehydrogenation. This activity enhancement is related to the modification of d states in the Pd monolayer shell by the strong ligand effect between Ag core and Pd shell, rather than the tensile strain effect by Ag core. In particular, the absence of dz(2)-r(2) density of states near the Fermi level in the Pd monolayer shell (which originated from the substantial charge transfer from Ag to Pd) is the main reason for the increased H-2 production from HCOOH decomposition.