Plasma-Induced Construction of S-Scheme Heterojunctions Enables Photo-Enhanced Peroxymonosulfate Activation for Gaseous Toluene Removal

Abstract

Selective activation of peroxymonosulfate (PMS) represents an efficient route to generate the reactive oxygen species (ROS) for the degradation and deep mineralization of organic pollutants, but its activity and selectivity are remarkably lower than what is needed. Herein, an S-scheme heterojunction is developed to effectively modify surface electronic properties and introduce abundant oxygen vacancies, thereby enabling photo-enhanced PMS activation for selective removal of gaseous toluene. S-scheme heterojunction is fabricated by in situ growth of ultrathin Co₃O₄ nanoparticles on g-C₃N₄ nanosheets through a rapid plasma treatment. The electronic field at the S-scheme heterostructure interface of Co₃O₄/g-C₃N₄ (COCN) facilitates charge transfer, selectively removing low-redox electrons and holes while separating high-redox ones. Photo-excited electrons promote the Co³⁺/Co²⁺ redox cycle, thereby enhancing ROS generation and creating continuous PMS activation sites. The COCN catalyst demonstrates remarkably high degradation efficiency (90.2%) and mineralization rate (68.5%) for flowing gaseous toluene in aqueous solution. This study thus provides a feasible strategy for plasma-induced electronic modulation and offers new insights for future heterojunction design aimed at efficient PMS activation.