CaSnO₃: An Electrocatalyst for Two-Electron Water Oxidation Reaction to Form H₂O₂

The two-electron water oxidation reaction (2e-WOR) is a promising route for distributed electrochemical synthesis of hydrogen peroxide (H2O2), an effective and green oxidizer, bleaching agent, and antiseptic. To date, the best electrocatalyst for 2e-WOR, in terms of selectivity against the competing 4e-WOR to form O2, is BiVO4. Nevertheless, BiVO4 is unstable and has a high overpotential of ∼340 mV at 0.2 mA/cm2 for 2e-WOR. Herein, we use density functional theory to identify a new, efficient, selective, and stable electrocatalyst for 2e-WOR, i.e., the ternary oxide calcium stannate (CaSnO3). Our experiments show that CaSnO3 achieves an overpotential of 230 mV at 0.2 mA/cm2, peak Faraday efficiency of 76% for 2e-WOR at 3.2 V vs the reversible hydrogen electrode (RHE), and stable performance for over 12 h, outperforming BiVO4 in all aspects. This work demonstrates the promise of CaSnO3 as a selective and cost-effective electrocatalyst candidate for H2O2 production from water oxidation.