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 H₂ production from HCOOH in Ag₁₉@Pd₆₀ 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 H₂ formation via HCOOH decomposition compared to the pure Pd₇₉ 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 dz²-r² 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 H₂ production from HCOOH decomposition.