Efficient Electrochemical Reduction of Oxygen to Hydrogen Peroxide on the La ₂ NiO ₄ Perovskite Electrocatalyst

The two-electron oxygen reduction reaction (ORR) is a most promising and efficient approach to generate hydrogen peroxide (H2O2), yet its practical application is still hindered by the lack of high-performance and cost-effective electrocatalysts. Herein, a La2NiO4 perovskite oxide with low oxidation states of Ni sites and rich oxygen vacancies, produced through a simple sol–gel route, has been employed to trigger highly effective ORR catalysis for H2O2 electrosynthesis. The La2NiO4 material exhibits commendable ORR activity under alkaline conditions with exceptional H2O2 selectivity (∼88%) over a broad potential range (0.15–0.65). Furthermore, in an H-cell configuration, the catalyst reaches a maximum H2O2 production rate of 2.43 mM h–1 at −0.05 V and a peak Faradaic efficiency of 85.7% at 0.40 V. La2NiO4 achieved a sustainable H2O2 production rate of 2.58 mM h–1, with the concentration accumulating to 22.7 mM over 9 h. In situ Fourier-transform infrared (FTIR) and Raman spectroscopy further demonstrate the rapid kinetics of the *OOH-mediated 2e– ORR pathway on the La2NiO4 electrocatalyst. Density functional theory (DFT) calculations also elucidate that the favorable electronic structure of La2NiO4 with abundant Ni2+ species and oxygen vacancies significantly helps to lower the Gibbs free energy barrier of *OOH intermediates, ΔG*OOH, when compared to the typical LaNiO3 material. Practically, a remarkable electrochemical degradation ability of some organic pollutants is observed; especially, the degradation rate of methylene blue (MB) reaches 98% within 1 h. This work well elucidates the underlying ORR mechanism and offers theoretical and practical guidance for designing perovskite oxide catalysts toward selective H2O2 electrosynthesis and environmental remediation.