Comparative study of g-C₃N₄/Ag-based metals (V, Mo, and Fe) composites for degradation of Reactive Black 5 (RB5) under simulated solar light irradiation

In present work, a comparative study on the heterojunction formation between g-C3N4 and a series of Ag-based metal oxides (Ag4V2O7, AgFeO2 and Ag2Mo2O7) catalysts prepared via a facile hydrothermal method was conducted in the degradation of Reactive Black 5 (RB5). HRTEM, XRD, UV-vis, PL results confirmed that Ag-based metal oxides were successfully incorporated into the framework of g-C3N4. The optical properties of the prepared catalysts showed an enhanced light absorption in the visible light region and improved charge carrier's separation. Photoelectrochemical (PEC) analysis revealed that g-C3N4/Ag2Mo2O7 catalyst possessed remarkably faster charge transport and high conductivity compared to other samples. g-C3N4/Ag2Mo2O7 catalyst exhibited the best photocatalytic RB5 degradation of 96.8% after 50 min of simulated solar light irradiation. The photocatalytic activity followed the trend: g-C3N4/Ag2Mo2O7 > g-C3N4/Ag4V2O7 > g-C3N4/AgFeO2 > g-C3N4, in accordance with the amount •OH radicals determined by fluorescence spectroscopy. Effect of Ag2Mo2O7 loadings revealed that 20 wt% g-C3N4/Ag2Mo2O7 demonstrated the highest photodegradation efficiency of RB5 due to the high formation of •OH radicals in the photocatalytic reaction. The mechanistic study for degradation of RB5 was proposed for the improved photoactivity as evidenced by the radical scavenger's test. Moreover, the g-C3N4/Ag2Mo2O7 catalyst could be reused several times without significant loss of photoactivity, making it an excellent candidate to be used in wastewater remediation.