Hydrogen Peroxide Production from Pure Water by MXene/Co₉S₈ 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.