Bimetallic nanoporous Pd-Ag prepared by dealloying with polyvinylpyrrolidone and their electrocatalytic properties

Bimetallic nanoporous Pd-Ag solid solution alloys with hierarchical structure were prepared by dealloying melt-spun Al-Pd-Ag ribbons in a 10 wt% H₃PO₄ solution. Electrocatalytic properties of nanoporous Pd-Ag alloys were measured in comparison with the nanoporous Pd without Ag. Experimental results showed that the nanoporous Pd-Ag alloys displayed electrocatalytic properties superior to their Ag-free counterparts. In particular, the optimised composition was revealed to be Pd/Ag = 3/2 in atomic ratio in the precursor with fixed 85 at% Al alloys, which yielded in a peak current density in the nanoporous Pd-Ag alloy two times that of the pure Pd one. The electrocatalytic activity of nanoporous Pd-Ag alloy with refined microstructure was further increased up to three times of the pure Pd one by adding 1 mM polyvinylpyrrolidone (PVP) into the H₃PO₄ solution. The underlying mechanism of refinement was related to a restriction effect on the free diffusion of Pd and Ag under adsorption of the PVP macromolecules. The significant improvement in the electrocatalytic properties was attributed to the dual promotion by the electron transfer from PVP to Pd-Ag and by a synergistic effect between Pd and Ag.