Mechanically driven piezocatalytic wastewater-to-hydrogen conversion in two-dimensional SnSe nanosheets

Abstract

Piezocatalysis is an emerging mechano-to-chemistry energy conversion technique that uses mechanically generated positive and negative charges to drive chemical reactions, opening broad opportunities in environmental remediation and energy conversion. However, most reported systems utilize only one type of charge for a single target reaction, leading to inefficient charge use. Here, we demonstrate that two-dimensional SnSe nanosheets can simultaneously use positive charges for pollutant degradation and negative charges for H2 evolution, thereby enabling mechanically driven piezocatalytic wastewater-to-hydrogen conversion. Under ultrasonic excitation at 80 kHz and 120 W, the SnSe nanosheets act as a bifunctional piezocatalyst, achieving a Rhodamine B degradation efficiency of 97.2% and an H2 yield of 1047.3 μmol g−1 within 2 h. The system also shows adaptability to different pollutant concentrations, pH values, pollutant species, and simulated mixed-pollutant wastewater. A flow-type piezocatalytic device further enables continuous H2 production and pollutant degradation beyond conventional batch tests. Mechanistic studies reveal that piezoelectrically generated positive charges promote hydroxyl radical generation for pollutant degradation, while negative charges facilitate H2 evolution through the *H intermediate. This work demonstrates a bifunctional charge utilization strategy for integrating wastewater purification with hydrogen production in a mechanically driven piezocatalytic system.