Boosting alkaline hydrogen electrooxidation on an unconventional fcc-Ru polycrystal

Abstract

Precisely controlling the crystalline phase structure and exposed facets at the atomic level opens up a new avenue for efficient catalyst design. Along this line, we report an unconventional face-centered cubic (fcc) Ru with twinned structure and stacking-fault defects as a competent electrocatalyst towards alkaline hydrogen oxidation reaction (HOR), which is now a major obstacle for the commercialization of anion exchange membrane fuel cells (AEMFC). With conventional hexagonal close packing (hcp) Ru as the counterpart, a novel scope from the phase-engineering is introduced to identify the activity origin and provide fundamental understanding of the sluggish HOR kinetics in alkaline medium. Systematic electrochemical analysis assisted by deconvoluting the hydrogen (H) desorption peaks indicates the superior performance of fcc Ru origins from the structure defects and higher proportion of the most active sites. DFT calculations, together with CO-stripping voltammograms further corroborate the stronger hydroxyl species (OH*) affinity lead to the higher activity on these sites. Meanwhile, it also demonstrates the H* adsorption/desorption on polycrystalline Ru among the conventional “hydrogen region” is accompanied by the surface bound OH* in alkaline medium, which is of great significance for subsequent alkaline HOR exploration and catalyst design.