HCOOH dissociation over the Pd-decorated Cu bimetallic catalyst: The role of the Pd ensemble in determining the selectivity and activity

Pd-decorated Cu bimetallic catalysts experimentally exhibited better catalytic performance toward hydrogenation reaction than the single Pd or Cu catalyst. This study is expected to identify the role of the Pd ensemble in determining the activity and selectivity, thus, HCOOH dissociation over the Pd-decorated Cu catalysts with different surface Pd distribution is fully examined by employing density functional theory calculations, including Pd1Cu8, Pd3Cu6, Pd6Cu3 and Pd9Cu0 catalysts, which are compared to the single Pd and Cu catalysts. The results found the Pd ensemble on the Pd6Cu3 and Pd9Cu0 surfaces with the Pd/Cu ratio of 6/3 and 9/0 exhibit higher selectivity and activity toward CO2 formation via the COOH intermediate, especially, Pd6Cu3 is superior to the single Pd; whereas the isolated Pd atom on the Pd1Cu8 and Pd3Cu6 surfaces with the Pd/Cu ratio of 1/8 and 3/6 dominantly produce CO via the COOH intermediate. Further, the structural and electronic properties reveal the role of the Pd ensemble in determining the catalytic performance of HCOOH dissociation. Our results provide a valuable clue and evaluation method in designing low-cost catalyst with the noble metal-decorated the non-noble metal catalysts, which can exhibit better catalytic performance by forming the surface ensemble of the noble metal.