Construction of a dual Z-scheme g-C3N4/BiOI/Ag2CrO4 ternary heterojunction for highly efficient visible-light photocatalytic degradation of Sudan Red III

Abstract

This study reports the successful fabrication of a novel ternary heterojunction photocatalyst, denoted as CBA (g-C3N4/BiOI/Ag2CrO4), featuring a double Z-scheme charge transfer pathway aimed at the effective degradation of the toxic azo dye Sudan Red III under visible light. The synthesis commenced with the fabrication of porous g-C3N4 via calcination coupled with a subsequent etching process. BiOI nanospheres were then grown onto the g-C3N4 substrate via a hydrothermal route. Subsequently, Ag2CrO4 nanoparticles were anchored on the g-C3N4/BiOI composite via a straightforward precipitation technique. The experimental evidence confirm successful formation of a ternary heterojunction, which exhibits a mesoporous structure and enhanced visible-light absorption. Evaluation of photocatalytic performance revealed that the optimized CBA catalyst (containing 30% g-C3N4/BiOI) attained a Sudan Red III degradation efficiency of 82.37% under 90-min visible-light irradiation, with a pseudo-first-order rate constant of 0.01944 min‒1. This constant value is 31.35 times that of the binary g-C3N4/BiOI system and 1.99 times that of individual Ag2CrO4. The remarkable photocatalytic enhancement is attributable to the established dual Z-scheme mechanism. This configuration effectively facilitates photogenerated charge separation, broadens visible-light absorption, and maintains high redox potentials. Thus, this work advances the design of efficient g-C3N4-based heterojunction systems, offering a viable strategy for photocatalytic purification of dye wastewater.