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 (H 2 O 2 ), yet its practical application is still hindered by the lack of high-performance and cost-effective electrocatalysts. Herein, a La 2 NiO 4 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 H 2 O 2 electrosynthesis. The La 2 NiO 4 material exhibits commendable ORR activity under alkaline conditions with exceptional H 2 O 2 selectivity (∼88%) over a broad potential range (0.15–0.65). Furthermore, in an H-cell configuration, the catalyst reaches a maximum H 2 O 2 production rate of 2.43 mM h –1 at −0.05 V and a peak Faradaic efficiency of 85.7% at 0.40 V. La 2 NiO 4 achieved a sustainable H 2 O 2 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 La 2 NiO 4 electrocatalyst. Density functional theory (DFT) calculations also elucidate that the favorable electronic structure of La 2 NiO 4 with abundant Ni 2+ species and oxygen vacancies significantly helps to lower the Gibbs free energy barrier of *OOH intermediates, Δ G *OOH, when compared to the typical LaNiO 3 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 H 2 O 2 electrosynthesis and environmental remediation.