Understanding the role of Pd:Cu ratio, surface and electronic structures in Pd-Cu alloy material applied in direct formic acid fuel cells

Aiming at illustrating the role of Pd:Cu atomic ratio for Pd-Cu alloy catalyst in HCOOH oxidation and the effects of surface and electronic structures on the activity and selectivity of HCOOH oxidation, DFT calculations are employed to investigate the underlying mechanism of HCOOH oxidation over different surfaces of PdCu and Pd3Cu with different Pd: Cu atomic ratios based on the Wullf construction. The results show that HCOOH oxidation on PdxCu(x = 1, 3) dominantly goes through the mechanism via the COOH intermediate path. Both Pd3Cu and the pure Pd exhibit better selectivity toward CO2 formation than PdCu in HCOOH oxidation; Pd3Cu also presents better activity toward CO2 formation than the pure Pd and PdCu. Compared to the pure Pd, Pd3Cu not only decrease the catalyst cost, but also reduce the adsorption ability of CO and enhance the ability of anti-CO position, and therefore increases the stability of Pd-based catalysts. Cu atoms of Pd3Cu donate the electrons to Pd atoms with the trimer to realize bimetallic synergetic effect in HCOOH oxidation. It is expected that the method applied in this study can provide a clue for the design and evaluation of bimetallic alloy catalysts in clean energy technology development.