New insight to piezocatalytic peroxymonosulfate activation: The critical role of dissolved oxygen in mediating radical and nonradical pathways

This study leverages piezocatalysis to accelerate redox reactions in heterogeneous peroxymonosulfate (PMS) activation. We syntheized few-layered molybdenum disulfide (MoS2) nanosheets as the piezoelectric catalyst for ultrasonic vibration (US)-coupled PMS system toward enhanced pollutant abatement. Scavenger tests, dissolved oxygen (DO) exclusion experiment and electron paramagnetic resonance (EPR) identify that sulfate radical (SO4•−) and singlet oxygen (1O2) are the primary ROS in the US/MoS2/PMS system. Particularly, O2•− is a vital intermediate for 1O2 generation, and multiple formation pathways of 1O2 were proposed in the US/MoS2/PMS system. With the assistance of DO and ultrasound, the utilization efficiency and activity of PMS will be remarkably increased because the majority of PMS evolves into more reactive SO4•− and 1O2 for pollutant degradation. This work not only provides mechanistic insights into the interconnected regimes of piezocatalysis and heterogeneous Fenton-like reactions, but also achieves high chemical efficiency for sustainable water remediation.