Charge transfer regulation of nickel oxide-nickel selenide hexagonal nanosheets with rich oxygen vacancies for efficient hydrogen peroxide electrosynthesis

Electrochemical synthesis of H₂O₂via 2-electron oxygen reduction reaction (2e-ORR) renders sustainable alternative to anthraquinone process. However, extensively developed carbon-based electrocatalysts commonly present vulnerability and decayed selectivity in higher reductive potentials. Here, based on the density functional theory simulations, the 2e-ORR capability of oxygen vacancy-rich NiO with exposed (001) is revealed. The predicted end-on manner of oxygen adsorption on the Ni sites contributes the preservation of OO bonds and prevents the over-reduction of OOH* to H₂O, thereby facilitates H₂O₂ formation. Moreover, the according NiO catalyst is experimentally prepared and decorated with island-like NiSe₂, which switches the rate-determining step of ORR from the first to second charge transfer with lowered Tafel slope. Consequently, the developed NiO-NiSe₂ catalysts achieve excellent Faraday efficiency of >95 % within a wide electrochemical window (0-0.6 V_RHE) and deliver stable H₂O₂ yield of ∼1.2 mol g_cat^-1 h^-1 for over 50 h, overwhelming most transition metal compounds. Meanwhile, practical pulp bleaching is also enabled by real-time production of H₂O₂ from NiO-NiSe₂-based flow cells. This work offers new insights into the design of non-carbon catalysts towards 2e-ORR, deepening the understanding of transition metal compounds in electrocatalysis.