Hierarchical RuO2/Co3O4 Heterostructures Enable Efficient Bromine-Mediated Electrochemical Ethylene Epoxidation via Electronic and Structural Synergy

Abstract

The conventional industrial process for ethylene epoxidation (EO) is challenged by high energy consumption and substantial carbon emissions. Bromine-mediated electrochemical EO synthesis offers a promising alternative, yet its economic viability is constrained by the reliance on high amount of precious metal catalysts for the anodic bromine evolution Reaction (BrER). Herein, we report a hierarchical and low-precious-metal RuO2/Co3O4 heterostructure, constructed by anchoring highlydispersed RuO2 nanoparticles onto Co3O4 nanorod arrays. The optimized RuO2/Co3O4 catalyst exhibits fast BrER reaction kinetics, high bromine-to-EO Faradaic efficiency (>85%) over a wide current density range of 50-200 mA cm⁻², and stable operation for over 20 h, outperforming most the state-of-the-art BrER catalysts reported. Mechanistic studies combining XPS, in situ Raman spectroscopy, and DFT calculations reveal that interfacial charge transfer induces a unique electronic environment that weakens Br adsorption via a pre-oxidative interaction, while simultaneously stabilizing the cobalt oxide lattice against anodic reconstruction. This dual electronic-structural synergy enables high activity with reduced Ru loading, offering a viable strategy for developing durable and economical BrER anodes toward sustainable electrochemical ethylene epoxidation.