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

The development of efficient and sustainable hydrogen peroxide (H 2 O 2 ) production technologies is of great significance. In this work, a Ti 3 C 2 /Co 9 S 8 heterojunction piezocatalyst was successfully designed and synthesized via a one-step hydrothermal method, enabling highly efficient H 2 O 2 generation from pure water using ultrasonic vibration. Comprehensive characterizations confirmed that Co 9 S 8 nanoparticles were uniformly dispersed on the layered Ti 3 C 2 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 Co 9 S 8 to Ti 3 C 2, 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 Ti 3 C 2 /Co 9 S 8 -2 catalyst achieved a remarkable H 2 O 2 production rate of 4498.56 μmol·g –1 ·h –1, which is 1.63 and 5.92 times higher than those of pure Co 9 S 8 (2756.16 μmol·g –1 ·h –1 ) and Ti 3 C 2 (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.