Bifunctional Oxygen-Defect Bismuth Catalyst toward Concerted Production of H₂O₂ with over 150% Cell Faradaic Efficiency in Continuously Flowing Paired-Electrosynthesis System.

Abstract

The electrosynthesis of hydrogen peroxide (H₂O₂) from O₂ or H₂O via the two-electron (2e^-) oxygen reduction (2e^- ORR) or water oxidation (2e^- WOR) reaction provides a green and sustainable alternative to the traditional anthraquinone process. Herein, a paired-electrosynthesis tactic is reported for concerted H₂O₂ production at a high rate by coupling the 2e^- ORR and 2e^- WOR, in which the bifunctional oxygen-vacancy-enriched Bi₂O₃ nanorods (O_v-Bi₂O₃-EO), obtained through electrochemically oxidative reconstruction of Bi-based metal-organic framework (Bi-MOF) nanorod precursor, are used as both efficient anodic and cathodic electrocatalysts, achieving concurrent H₂O₂ production at both electrodes with high Faradaic efficiencies. Specifically, the coupled 2e^- ORR//2e^- WOR electrolysis system based on such distinctive oxygen-defect Bi catalyst displays excellent performance for the paired-electrosynthesis of H₂O₂, delivering a remarkable cell Faradaic efficiency of 154.8% and an ultrahigh H₂O₂ production rate of 4.3 mmol h^-1 cm^-2. Experiments combined with theoretical analysis reveal the crucial role of oxygen vacancies in optimizing the adsorption of intermediates associated with the selective two-electron reaction pathways, thereby improving the activity and selectivity of the 2e^- reaction processes at both electrodes. This work establishes a new paradigm for developing advanced electrocatalysts and designing novel paired-electrolysis systems for scalable and sustainable H₂O₂ electrosynthesis.