Regulating Interfacial Hydrogen-Bonding Connectivity by Oxygen Vacancies-Driven [Fe(CN)₆]³⁻ Coordination for Boosting Hydrogen Peroxide Electrosynthesis

Abstract

The inherent hydroxide-rich (OH⁻) environment in alkaline media facilitates the two-electron oxygen reduction reaction (2e⁻ORR). However, the strong interaction between alkali metal cations and solvated water molecules significantly reduces the connectivity of the hydrogen bond network within the alkaline electric double layer, thereby severely impeding rapid proton transport at the electrode surface. Herein, we rationally designed ZnO with oxygen vacancies-driven [Fe(CN)₆]³⁻ coordination (denoted as Fe(CN)₆-ZnO-V_O) as an efficient 2e⁻ORR catalyst for H₂O₂ electrosynthesis. We demonstrate that the locally coordinated [Fe(CN)₆]³⁻ establishes pathways for rapid proton transfer at the electrode surface by forming a hydrogen bond network with interfacial water molecules. Concurrently, this configuration significantly reduces the energy barrier of the *OOH intermediate. These synergistic effects collectively optimize the electrocatalytic performance for H₂O₂ production under alkaline conditions. As expected, the Fe(CN)₆-ZnO-V_O delivers a significantly increased current density of 130 mA cm⁻² that is much higher than ZnO (32 mA cm⁻²), as well as a superior H₂O₂ production rate of 9.41 mol g_cat⁻¹ h⁻¹ and a high faradaic efficiency of exceeds 90%. Our study highlights the crucial role of interfacial hydrogen-bonding connectivity and provides theoretical and technical guidance for developing reliable strategies to enhance the electrocatalytic properties of 2e⁻ORR.

Keywords

hydrogen peroxide / hydrogen-bond network / oxygen vacancy / surface coordination environment / synergistic effect

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