Enhanced Flexocatalytic H₂O₂ Production via Oxygen Reduction Pathway in a g-C₃N₄/SrTiO₃ II-Scheme Heterojunction

Hydrogen peroxide (H₂O₂) is an essential industrial oxidant, yet its conventional production remains energy-intensive and generates hazardous byproducts. Flexocatalysis has emerged as a promising mechanochemical strategy that overcomes the symmetry constraints of piezoelectric materials, allowing a wider range of semiconductors to participate in mechano-driven redox reactions. However, this green approach faces challenges due to inefficient mechanochemical energy conversion and insufficient active sites. In this study, the g-C₃N₄/SrTiO₃ nanocomposites are prepared by initially hydrothermally-synthesizing SrTiO₃, which was then mechanically mixed with g-C₃N₄ and calcined. The optimized heterojunction demonstrates an elevated H₂O₂ production rate of 645.1 μmol·g^-1·h^-1 when subjected to ultrasonication, outperforming the yields of pristine g-C₃N₄ and SrTiO₃ by 2.7 and 3.7 folds, respectively. The improved efficiency is attributed to the effective spatial separation of mechano-induced charges across the heterointerface, which suppresses charge recombination and thereby enhances the overall redox efficiency. Mechanistic investigations, including electron spin resonance spectroscopy and radical trapping experiments, collectively demonstrate that the sequential two-step single-electron oxygen reduction serves as the predominant pathway for H₂O₂ generation. This study highlights the potential of heterojunction engineering in advancing flexocatalytic systems and presents a scalable, sustainable strategy for ultrasound-driven H₂O₂ synthesis.