Revealing the origin of single-atom W activity in H2O2 electrocatalytic production: Charge symmetry-breaking

The low-energy electrochemical production of hydrogen peroxide (H₂O₂) has garnered significant attention as a viable alternative to traditional industrial routes, with the goal of achieving carbon neutrality. For their H₂O₂ selectivity in the two-electron oxygen reduction reaction (ORR), the coordination environment of tungsten (W)-based materials is critical. In this study, atomically dispersed W single atoms were immobilized on N-doped carbon substrates by a facile pyrolysis method to obtain a W single-atom catalyst (W-SAC). The coordination environment of an isolated W single atom with a tetra-coordinated porphyrin-like structure in W-SAC was determined by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy analysis. Notably, the as-prepared W-SAC showed superior two-electron ORR activity in 0.1 M KOH solution, including high onset potential (0.89 V), high H₂O₂ selectivity (82.5%), and excellent stability. By using differential phase contrast-scanning transmission electron microscopy and density functional theory calculations, it is revealed that the charge symmetry-breaking of W atoms changes the adsorption behavior of the intermediates, leading to enhanced reactivity and selectivity for two-electron ORR. This work broadens the avenue for understanding the charge transfer of W-based electrocatalytic materials and the in-depth reaction mechanism of SACs in two-electron ORR.