Mechanistic insights into the reaction pathway for efficient cationic dye photocatalytic degradation and the importance of the enhanced charge isolation over dual Z-scheme CeO2/BiOCl/Ag2WO4 photocatalyst

Abstract

Fabricating a multi-component heterojunction system with enhanced charge isolation efficacy remains challenging. A photoactive CeO2/BiOCl/Ag2WO4 heterojunction was successfully constructed using a co-precipitation technique to degrade crystal violet and methylene blue dyes. It was found through a combination of characterization and experiments that the dual Z-scheme system not only augmented the charge isolation and migration efficiency but also maintained superior redox ability with extended visible light absorption capacity. In the CeO2/BiOCl/Ag2WO4 system, 97 % of methylene blue and 98 % of crystal violet were degraded in 75 min using 50 mg/L of ternary photocatalyst. The rate of reaction of CeO2/BiOCl/Ag2WO4 for methylene blue (0.0445 min−1) and crystal violet (0.05053 min−1) exhibited a multi-fold increase in comparison to the bare photocatalysts. The electron spin resonance (ESR) analysis has remarkably identified hydroxyl and superoxide radicals (•OH, •O2−) as the primary reactive species in the photodegradation process. Liquid chromatography-mass spectrometry analysis was utilized to obtain potential degradation pathways for methylene blue and crystal violet, respectively. The dual charge transferal mechanism by the ternary photocatalyst resulted in a significant increase in photocatalytic activity. It provided new perspectives on the principles guiding the rational development of a multicomponent system for environmental remediation.