Breaking the Scaling Relationship in Two-Electron Water Oxidation via Designing Dual Active Centers for Efficient H2O2 Electrosynthesis

A two-electron water oxidation reaction (2e-WOR) over nonprecious and environmentally friendly electrocatalysts like SnO₂ holds great promise to replace the traditionally energy-intensive anthraquinone process for valuable hydrogen peroxide (H₂O₂) synthesis, while it is subjected to poor activity and selectivity due to the inherent scaling limitation of intermediate adsorption on active sites. Herein, we report a theory-guided dual active center engineering of SnO₂ quantum dots, achieved by introducing oxygen vacancy (O_V) and Zn dopant (Zn_D), to break the scaling limitation for promoting 2e-WOR. Physicochemical characterizations, including operando infrared spectroscopy, isotope-labeling mass spectrometry, quasi in situ electron paramagnetic resonance, ¹¹⁹Sn Mössbauer spectroscopy, and X-ray absorption spectroscopy, along with theoretical calculations, unveil that O_V activates the water molecule to dissociate it to *OH, and Zn_D facilitates the subsequent *OH coupling, collectively boosting H₂O₂ production. Consequently, the resulting Zn/SnO_2–x exhibits a high Faradaic efficiency of 87.5% at 200 mA cm^–2, a fast production rate of 52.7 μmol cm^–2 min^–1, and robust stability of 60 h for H₂O₂ generation, superior to most reported 2e-WOR electrocatalysts. In addition, the on-site generated H₂O₂ can be used as a typical oxidant for ciprofloxacin pollutant degradation and selective propylene oxidation to propylene glycol feedstock.