CaSnO ₃: An Electrocatalyst for Two-Electron Water Oxidation Reaction to Form H ₂ O ₂

The two-electron water oxidation reaction (2e-WOR) is a promising route for distributed electrochemical synthesis of hydrogen peroxide (H ₂ O ₂ ), 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 O ₂ , is BiVO ₄ . Nevertheless, BiVO ₄ is unstable and has a high overpotential of ∼340 mV at 0.2 mA/cm ² 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 (CaSnO ₃ ). Our experiments show that CaSnO ₃ achieves an overpotential of 230 mV at 0.2 mA/cm ² , 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 BiVO ₄ in all aspects. This work demonstrates the promise of CaSnO ₃ as a selective and cost-effective electrocatalyst candidate for H ₂ O ₂ production from water oxidation.