Tailoring Zn ₂ SnO ₄ inverse spinel via Co doping: enhanced two-electron water oxidation for efficient H ₂ O ₂ electrosynthesis

Developing low-cost, high-performance electrocatalysts is crucial for industrializing in-situ H 2 O 2 production via the two-electron water oxidation reaction (2e-WOR). As a typical inverse spinel oxide, Zn 2 SnO 4 integrates the high selectivity of Zn-based materials and the superior electron transport of Sn-based materials, yet its pristine form suffers from insufficient active sites and high charge-transfer resistance.Herein, a series of Co-doped Zn 2 SnO 4 catalysts were synthesized via hydrothermal treatment followed by calcination. Co 2+ was successfully incorporated into the inverse spinel lattice without phase segregation, inducing systematic lattice contraction and tunable oxygen vacancy concentration. Optimal 6% Co doping yields precisely controlled particle size, maximized electrochemical surface area, and significantly reduced charge-transfer impedance. Zn 2 SnO 4 -6%Co exhibited superior 2e-WOR performance: a low plateau potential of 2.4 V, cumulative H 2 O 2 concentration of 850 mg•L -1 within 120 min, peak Faradaic efficiency of 87.69%, and a high production rate of 36.40 mmol•g cat -1 •min -1 , alongside exceptional stability over 24 h. DFT calculations reveal that Co doping modulates the local electronic structure, optimizing •OH adsorption energy to a near-ideal range and facilitating intermediate desorption. This work establishes a clear structure-activity relationship from atomic-scale electronic modulation to macroscopic performance enhancement, offering a rational doping strategy for designing efficient metal oxide electrocatalysts for green H 2 O 2 synthesis.