Enhancing the Oxygen Reduction Reaction Performance by Modifying the Surface of Platinum Nanoparticles

The depressing oxygen reduction reaction (ORR) performance has impeded the commercialization of proton exchange membrane fuel cells. As a surface-sensitive reaction, the surface structure of the electrocatalyst has a crucial impact on the ORR. Herein, Pt nanoparticle surfaces were modified with the aid of Ag, which was deposited on the surface of Pt nanoparticles and was etched away through cyclic voltammetry (CV). After surface modification, the step density of the Pt nanoparticles was observed to decrease, according to high-resolution transmission electron microscopy images, which could contribute to the positive shift of the Pt4f binding energy and the improved ability to prevent Pt from being oxidized, as seem by using X-ray photoelectron spectroscopy. Furthermore, the peak potential increase for the surface metal-oxide reduction during CV was consistent with the impact of the step density reduction. After surface modification, the Pt nanoparticles showed improved ORR performance, according to half-cell tests. At the atomic scale, the decrease in the number of low-coordination atoms on the surface steps, which exhibit stronger interactions with O-ads/OHads compared with atoms on terraces, could lead to the enhanced ORR performance.