Superior efficiency hydrogen peroxide production in acidic media through epoxy group adjacent to Co-O/C active centers on carbon black

Abstract

The coordination environment of transition metals in single-atom catalysts (SACs) is crucial for tuning the pathway of the electrocatalytic oxygen reduction reaction (ORR). However, it is significantly difficult to simultaneously and precisely control the first and second coordination structure near the metal active center. Herein, we report that the activated carbon black was used to anchor transition metals’ single atoms with a similar first and second coordination structure. As a result, Co-SACs exhibit an extraordinary performance for ORR to produce H2O2, where a current density of around ∼2.8 mA cm−2 at 0.1 V vs RHE by rotating ring-disk electrodes and a high yield rate of 110.2 mmol gmetal−1 h−1 at the potential of 0.3 V vs RHE in a gas diffusion electrodes (GDEs) cell, with a high positive onset potential of 0.65 V vs RHE and a >80% selectivity of H2O2 at the potential range from 0.25 to 0.65 V vs RHE, respectively. The combined experimental observations and theoretical calculations indicate that the catalytic active center lies in the Co-C3/O1 moiety of the adjacent epoxy group. The possible position of the epoxy group in the second coordination sphere was further revealed. Moreover, Co-SACs were employed in an electrocatalytic GDEs cell for distributed generation of H2O2 in the acidic media, and coupling Fe-SACs-based Fenton filter or electro-Fenton setup with the H2O2 electrolytic generator delivers an efficient and distributable wastewater treatment system. Our study provides a promising and alternative route for on-site H2O2 production coupling the practical application process.