Modulating coordination environment of Fe single atoms for high-efficiency all-pH-tolerated H2O2 electrochemical production

Designing atomically dispersed non-precious metal catalysts for 2e(-) oxygen reduction reaction (ORR) is an appealing strategy to harness O-2-to-H2O2 chemistry. Nevertheless, prevailing M-N-C single-atom catalysts (SACs) might still not satisfy the directional regulation of ORR selectivity, hence fail to uphold scalable H2O2 electrosynthesis with a high yield. Herein, we report the precise synthesis of (O,N)-coordinated Fe SAC (FeN2O2) and relating investigation of its performance in H2O2 production over a wide pH range, in comparison with the FeN4 counterpart. Density functional theory simulations reveal that the coordination chemistry engineering has a profound influence on the strength of the oxygen intermediate adsorption. The electron delocalization of M-O configuration readily lowers the d-band center of the Fe metal, which is beneficial to weakening the intermediate adsorption capability and promoting the 2e(-) ORR process. The thus-derived FeN2O2 exhibits impressive selectivity in a wide pH range, particularly reaching 95% in alkaline conditions. Furthermore, our designed gas-diffusion electrode enables a favorable H2O2 yield (300 mmol L-1) at a current density of 60 mA cm(-2) for 50 h. This work is anticipated to inspire the rational design of definitive SAC architecture for practically feasible electrochemical production of H2O2 toward environmental remediation.