Piezoelectric charges elicited a chain reaction of sulfite activation: Performance and mechanism.

[Display omitted] • The piezoelectric charges are applied to activate sulfite to generate reactive specie for enhancing the metronidazole degradation, and the dominant reactive specie is sulfate radical. • The mechanism for piezoelectric sulfite activation is proposed. That is, the piezoelectric holes react with sulfite to produce sulfite radical and trigger a chain reaction. • The chain reaction of sulfite elicited by piezoelectric charges can be applied for practical water remediation. • This system can degrade metronidazole and reduce its environmental toxicity. Taking use of mechanical-to-chemical energy is a promising way to develop sustainable catalysis, but it is hindered by the low reactive oxygen species (ROS) yield induced directly by intrinsic carriers. In this paper, by coupling piezocatalysis with sulfite (S(IV)) activation via a g-C 3 N 4 /S(IV)/US ternary system, piezoelectric holes react with S(IV), triggers a chain reaction and brings about a considerable ROS generation for enhancing the degradation of organic pollutants. As a result, profiting from the crucial electron-gaining ability of holes, the k obs of metronidazole removal after adding g-C 3 N 4 increases by 2.02 times from 0.0161 min−1 to 0.0325 min−1. This enhancement occurs because the piezoelectric holes can both promote the transfer of electrons from S(IV) to g-C 3 N 4 and the generation of sulfite radical (SO 3 −). By this way, the SO 3 − rapidly reacts with the dissolved oxygen to generate sulfate radical and hydroxyl radical through a chain reaction for water remediation. This study provides a novel strategy to maximize the utilization of piezoelectric holes. [ABSTRACT FROM AUTHOR]