Nanoporous PdCr alloys as highly active electrocatalysts for oxygen reduction reaction.

A simple and convenient dealloying method is used to prepare nanoporous (NP) PdCr alloys with uniform ligament dimensions and controllable bimetallic ratio. The structural characterization methods demonstrate that the NP-PdCr alloy is comprised of a nanoscaled interconnected network skeleton and hollow channels extending in all three dimensions. Electrocatalytic measurements indicated that the as-made NP-Pd75Cr25 alloy exhibits superior specific and mass activities as well as higher catalytic stability toward oxygen reduction reaction compared with NP-Pd67Cr33, NP-Pd, and commercial Pt/C catalysts. X-ray photoelectron spectroscopy and density functional theory calculations both demonstrate that the weakened Pd-O bond and improved ORR performances depend on the downshifted d-band center of Pd due to the alloying of Pd with Cr (25 at%). It is expected that the as-made NP-PdCr alloy has prospective application as a cathode electrocatalyst in fuel-cell-related technologies with the advantages of superior overall ORR performances, unique structural stability, and easy preparation.