Palladium Nanobelts with Expanded Lattice Spacing for Electrochemical Oxygen Reduction in Alkaline Media

Pd has been considered as a promising catalyst for the electrochemical oxygen reduction reaction (ORR) in an alkaline environment. However, the strategies and fundamental understanding for improving the catalytic activity and durability of pure Pd are still challenging. Here, we develop a Pd nanobelt (NB) catalyst with expanded lattice spacing, showing both ultrahigh activity and excellent durability. Surprisingly, the surface-specific and mass activities of carbon-supported Pd NBs catalyst are 4-fold and 6-fold higher than the counterparts of the commercial Pt/C catalyst in an alkaline medium of 1.0 M KOH. After the ultralong durability test of 100 000-cycle potential sweeping, the nanostructure was still preserved and more than 80% of the surface-specific activity remained. The enhanced activity, analyzed by density functional theory (DFT) calculations, should be ascribed to the expanded lattice spacing, which could reduce the free energy (FE) of intermediates on the Pd surface and lower the overpotential for the ORR. Our work furthers the understanding of the excellent ORR catalysis of pure Pd with lattice expansion and casts light on the Pd-based catalyst design.