Enhanced Flexocatalytic H ₂ O ₂ Production via Oxygen Reduction Pathway in a g-C ₃ N ₄ /SrTiO ₃ II-Scheme Heterojunction

Hydrogen peroxide (H 2 O 2 ) 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-C 3 N 4 /SrTiO 3 nanocomposites are prepared by initially hydrothermally-synthesizing SrTiO 3, which was then mechanically mixed with g-C 3 N 4 and calcined. The optimized heterojunction demonstrates an elevated H 2 O 2 production rate of 645.1 μmol·g –1 ·h –1 when subjected to ultrasonication, outperforming the yields of pristine g-C 3 N 4 and SrTiO 3 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 H 2 O 2 generation. This study highlights the potential of heterojunction engineering in advancing flexocatalytic systems and presents a scalable, sustainable strategy for ultrasound-driven H 2 O 2 synthesis.