Applied Surface Science, Vol.462, 649-658, 2018
Theoretical investigations of HCOOH decomposition on ordered Cu-Pd alloy surfaces
Formic acid (HCOOH) decomposition is studied on four ordered Cu-Pd compounds (B2-type CuPd, L1(0)-type CuPd, L1(2)-type Cu3Pd, and L1(2)-type CuPd3) through systematic density functional calculations. The crystal structures and atomic compositions play a significant role to control activity and selectivity of catalysts. The O-H bond dissociation barrier of HCOOH is less than that of the C-H bond scission, and the most high selectivity for O-H/C-H dissociation is found on the single Pd atom alloyed in Cu lattice of L1(2) Cu3Pd(1 1 1) surface. However, the contiguous Pd atoms greatly facilitate hydrogen production from HCOOH, and the barriers are 0.44 and 0.73 eV for the dehydrogenation reactions on of HCOOH -> HCOO + H -> CO2 + 2H on L1(0) CuPd(1 1 1) surface. Though the CO formation pathway is energetically favorable for COOH decomposition on the ordered Cu-Pd surfaces except Pd-rich ordered CuPd3(1 1 1) surface, the adsorbed CO can be easily removed due to the weaker interaction compared with pure Pd surfaces. The calculated results indicate that L1(0) CuPd and L1(2) CuPd3 alloys are effective catalysts for formic acid decomposition with high catalytic selectivity and activity.