Boosting Piezoelectric Catalytic H ₂ O ₂ Production in Pure Water of Graphitic Carbon Nitride via Defect Engineering With Tunable Oxygen‐Doping

ABSTRACT Piezocatalytic conversion of mechanical energy into chemical energy offers a sustainable route for hydrogen peroxide (H ₂ O ₂ ) synthesis. However, its practical application is hampered by low polarization intensity, charge recombination, and the requirement of sacrificial agents. Herein, we report a one‐step co‐calcination strategy to introduce tunable oxygen defects into graphitic carbon nitride (g‐C ₃ N ₄ ), enabling efficient sacrificial‐agent‐free piezocatalysis in pure water. The optimized sample (CN‐40) delivers a remarkable H ₂ O ₂ yield of 671 µmol g ⁻¹ h ⁻¹ , four times higher than pristine g‐C ₃ N ₄ , surpassing most reported metal‐free piezocatalysts. Structural analyses reveal that oxygen incorporation disrupts the tri‐s‐triazine symmetry, enhances lattice distortion, and strengthens piezoelectric polarization. Electrochemical and spectroscopic studies confirm the increased carrier density, reduced charge‐transfer resistance, and generation of reactive oxygen species under ultrasonic excitation. Band structure analysis and COMSOL simulations further clarify the synergistic mechanism of single‐electron water oxidation and oxygen reduction reactions. This work demonstrates a defect‐engineering strategy to overcome intrinsic limitations of g‐C ₃ N ₄ , providing both mechanistic insights and practical solutions for green chemical synthesis and environmental remediation.