Hydrogen Peroxide Production from Pure Water by MXene/Co 9 S 8 Heterojunction Piezocatalyst

The development of efficient and sustainable hydrogen peroxide (H2O2) production technologies is of great significance. In this work, a Ti3C2/Co9S8 heterojunction piezocatalyst was successfully designed and synthesized via a one-step hydrothermal method, enabling highly efficient H2O2 generation from pure water using ultrasonic vibration. Comprehensive characterizations confirmed that Co9S8 nanoparticles were uniformly dispersed on the layered Ti3C2 MXene substrate, forming a well-defined heterojunction with intimate interfacial contact. X-ray photoelectron spectroscopy (XPS) analysis and ultraviolet photoelectron spectroscopy (UPS) measurements collectively confirmed directional electron transfer from Co9S8 to Ti3C2, providing direct evidence for the formation of a built-in electric field at the heterojunction interface. Under optimal ultrasonic vibration (40 kHz, 180 W), the optimized Ti3C2/Co9S8-2 catalyst achieved a remarkable H2O2 production rate of 4498.56 μmol·g–1·h–1, which is 1.63 and 5.92 times higher than those of pure Co9S8 (2756.16 μmol·g–1·h–1) and Ti3C2 (760.32 μmol·g–1·h–1), respectively. Piezocurrent and electrochemical impedance spectroscopy (EIS) measurements demonstrated that the enhanced catalytic performance was attributed to the superior piezoelectric response of the heterojunction, efficient charge separation, and reduced charge transfer resistance. Furthermore, the catalyst exhibited excellent stability over five consecutive cycles. This study provides an effective strategy for designing high-performance piezocatalysts for sustainable chemical production.