Boosting Oxygen Reduction to Hydrogen Peroxide Production over the LaNiO3 Perovskite Electrocatalyst with Tunable Oxygen Vacancies

Abstract

Sustainable H2O2 synthesis via the electrochemical two-electron oxygen reduction (2e– ORR) holds great promise, yet designing efficient and selective non-precious metal catalysts poses a significant challenge. Herein, controllable oxygen vacancies are engineered into LaNiO3 through a scalable defect-induced strategy, affording an active and stable electrocatalyst for 2e– ORR. Density functional theory (DFT) calculations first predict that LaNiO3 perovskite with an optimal oxygen vacancy concentration (LNO-8Ov) achieves a near-ideal ΔG*OOH value, placing it closest to the 2e– ORR volcano peak. Guided by these predictions, a one-step Ar plasma engraving method is employed to introduce tunable oxygen vacancies into LaNiO3, yielding a series of catalysts (LNO-PL X, X= 0, 5, 30, 60). Structural characterizations demonstrate that such treatment not only preserves the bulk perovskite phase while generating oxygen vacancies, increasing the Ni2+/Ni3+ ratio and generating amorphous regions, but also leads to an increased hole state density with the O 2p partial density of states (PDOS) shifting away from the Fermi level. The optimized LNO-PL 30 catalyst achieves a H2O2 selectivity of 71% at 0 V vs RHE, which is 24% higher than that of pristine LaNiO3 (47%), with an electron transfer number of 2.58. A volcano-type correlation between oxygen vacancy concentration and H2O2 selectivity was established, with LNO-PL 30 positioned at the apex of the volcano curve. In an H-type cell, LNO-PL 30 delivers an average H2O2 yield of 3.791 mM h–1 and maintains stable performance over 35 h. In addition, LNO-PL 30 delivers a maximum H2O2 production rate of 4.83 mM h–1 at 0 V vs RHE, with the Faradaic efficiency remaining consistently above 70% over a broad potential range. Post-ORR characterizations confirm the preserved structural and chemical stability of LNO-PL 30. In situ ATR-FTIR and Raman spectroscopy identify the *OOH key intermediate, while operando electrochemical impedance spectroscopy (EIS) demonstrates accelerated charge transfer and enhanced surface reaction kinetics. The O–O bond length of the adsorbed *OOH species shortens on oxygen vacancy-containing LaNiO3 (LNO-8Ov), which can suppress O–O bond cleavage. Furthermore, the catalyst enables in situ degradation of rhodamine B with over 80% efficiency across four cycles, highlighting its potential for pollutant degradation applications. This work provides a simple and effective defect-engineering approach to design high-performance perovskite electrocatalysts for sustainable H2O2 production.