Dual regulation platform in C3N4/C3N5.4 molecular heterojunctions for simultaneous photocatalytic oxidative and adsorption of arsenic

The conversion of extremely hazardous As(III) to less toxic As(V) and subsequent adsorption onto the catalyst surface holds an advisable process for arsenic contaminants treatment. However, the conflictual mechanism of oxidation and adsorptive remains a huge challenge and unexplored for arsenic removal. In this work, a dual regulation platform of C3N4/C3N5.4 molecular heterojunction was well designed and constructed. The optimized C3N4/C3N5.4 exhibited excellent photocatalytic As(III) oxidation rate and As(V) adsorption efficiency under water, fluorosilicic acid and phosphoric acid solutions. The excellent performance benefits from the molecular heterojunctions induced internal electronic interactions and a local polarization, which contributes to the formation of built-in electric field (BEF) for enhancing exciton dissociation and charge transfer. Furthermore, the optimized electronic structure serves as the adsorption and oxidation site for simultaneously promoting charge interaction with arsenic elements, which greatly reinforces the absorption of arsenic. Our work may pave the way to optimize the electronic structure of bifunctional material for arsenic remediation.