Highly visible active Ag2CrO4/Ag/BiFeO3@RGO nano-junction for photoreduction of CO2 and photocatalytic removal of ciprofloxacin and bromate ions: The triggering effect of Ag and RGO

Abstract Designing highly optical active photocatalytic heterojunctions with multi-pronged capabilities for environmental applications is still a challenge. In this work the photocatalytic potential of Ag 2 CrO 4 /Ag/BiFeO 3 @RGO was systematically tested via photo-reduction of BrO 3 − , degradation of Ciprofloxacin (CIF) and photo-reduction of CO 2 under broad light spectrum. Among various samples ABR-8 exhibits 99.6% BrO 3 − photoreduction and 96.3% CIF photo-oxidation in 90 min (nearly 96% in 60 min). ABR-11 (with 11 wt% RGO) selectively generates 180 μmol g −1 of CH 4 in 8 h under visible light (260 μmol g −1 under alkali activation) which is approximately 60 times than bare BiFeO 3 . The excellent performance of ABR series is attributed to successful formation of Z-scheme which assists in efficient charge transfer, reduced recombination and wide spectrum response. In addition the electron donation-mediation of plasmonic Ag 0 and adsorption-electron mediation of reduced graphene oxide has a triggering effect on reductive and oxidative capabilities. The band structure analysis, scavenging experiments and electron spin resonance studies make it possible to predict a suitable mechanism for bromate reduction, CIF degradation and CH 4 generation. Electron assisted BrO 3 − reduction, •OH and •O 2 − radicals powered CIF degradation by Z-scheme mechanism and multi-electron single step proton-coupled mechanism for highly selective CH 4 production were predicted. The best performing photocatalyst retain over 95% of performance over five consecutive runs. Suitable optimisations lead to higher performance from BiFeO 3 which bears many shortcomings via interfacial junction with Ag 2 CrO 4 with triggering effect from metallic Ag and RGO. Intelligently designed junctions can thus show strong photo-oxidative and reductive capabilities with further scope of fine tuning. Hence this developed heterojunction can be sustainably utilized for multi-pollutant removal and energy/fuel production under broad spectrum of light.