HCOOH decomposition over the pure and Ag-modified Pd nanoclusters: Insight into the effects of cluster size and composition on the activity and selectivity

[Display omitted] •The effects of cluster size and composition on the performance of HCOOH decomposition were examined.•CO2 formation is favored in kinetics than CO formation on the pure and Ag-modified Pd nanoclusters.•The small size of the pure and Ag-modified Pd nanoclusters exhibit higher activity and selectivity toward CO2 formation.•The Ag composition improves the activity and selectivity toward CO2 formation.•The better activity and selectivity is attributed to that the d-band center is more close to Fermi level. This work is designed to examine the size and composition effects of the pure and Ag-modified Pd nanoclusters on the activity and selectivity of HCOOH decomposition using DFT calculations and microkinetic modeling, Pdn(n = 13,38,55) and Agm@Pdn(m + n = 13,38,55) nanoclusters are considered. The results show that HCOOH decomposition dominantly undergoes COOH intermediate instead of HCOO intermediate, and CO2 formation is more favorable than CO formation. The pure and Ag-modified Pd nanoclusters with the small size exhibit higher activity and selectivity toward CO2 formation; meanwhile, when the nanocluster size is the same, compare to the pure Pd, the Ag composition improves the activity and selectivity toward CO2 formation, and decreases the usage of noble-metal Pd. The better catalytic performance is attributed to that the d-band center is more close to the Fermi level. The results provide a method for improving catalytic performance of Pd-based nanoclusters by adjusting the size and core composition of the nanocluster.