Constructing dual active sites for synergistic electrocatalysis of hydrogen oxidation: single-metal-atoms anchored on WC2O2 MXene

Abstract

The promising alkaline exchange membrane fuel cells (AEMFCs) are subject to the sluggish kinetics of anodic hydrogen oxidation reaction (HOR). Balancing the adsorption/desorption ability toward H* and OH* is considered to be an efficient way to improve the HOR efficiency, but is extremely hard on one active site. Here, single metal atoms (M_sa) anchored on W₂CO₂ MXene (W₂CO₂–M_sa) were built, including a series of 3d, 4d, and 5d metals. First-principles calculations indicate that the charge transfer between M_sa and W₂CO₂ induces an efficient dual-active site, i.e., M_sa as the OH* active site and its adjacent O atoms as the H* active site. The dual active sites on W₂CO₂–M_sa can not only avoid the competitive adsorption of H* and OH* but also display a synergistic catalytic effect towards the HOR. Remarkably, W₂CO₂–M_sa (M_sa = Mn, Fe, Co, Ir, and Pt) shows both high stability and superior HOR activity over bulk Pt, suggesting their huge potential as anodic electrocatalysts for AEMFCs.