Stable production of hydrogen peroxide over zinc oxide @ zeolitic imidazolate Framework-8 composite catalysts

A promising method of producing hydrogen peroxide (H₂O₂) is the electrochemical two-electron water oxidation reaction (2e^- WOR). In this process, it is important to design electrocatalysts that are both earth abundant and environmentally friendly, as well as offering high stability and production rates. The research of WOR catalysts, such as the extensively used transition metal oxides, is mainly focused on the modification of transition metal elements. Few studies pay attention to the protective heterostructure of metal oxides. Here, we demonstrate for the first time an organometallic skeleton protection strategy to develop highly stable WOR catalysts for H₂O₂ generation. Unlike the pure ZnO and zeolite imidazole framework-8 (ZIF-8) catalysts, ZnO@ZIF-8 enabled the production of hydrogen peroxide at high voltages. The experimental results demonstrate that the ZnO@ZIF-8 catalyst stably generates H₂O₂ even under a high voltage of 3.0 V vs. RHE, with a yield reaching 2845.819 μmolmin^-1 g^-1. ZnO@ZIF-8 shows a relatively low overpotential, with a current density of 10 mA cm^-2 and an overpotential of 110 mV. The ZnO@ZIF-8 catalyst's maximal FE value was 4.72 %. Moreover, the ZnO@ZIF-8 catalyst exhibits remarkable durability even after an extended 60-hour stability test. Operando Raman and theoretic calculation analyses reveal that the metal-organic skeleton being encapsulated on the metal oxide surface synergizes with each other, not only expanding the electrochemical surface area, but also adjusting the catalyst metal sites' adsorption capacity. A novel approach to the modification of 2e^- WOR metal oxide catalyst is presented in this work.