Recyclable, bifunctional composites of perovskite type N-CaTiO3 and reduced graphene oxide as an efficient adsorptive photocatalyst for environmental remediation

Graphene-semiconductor photocatalysts are of utmost interest for achieving visible light activity but there is ambiguity about the role played by graphene in these photocatalysts. Such photocatalysts exhibit both adsorptive and photocatalytic activities towards pollutant degradation. Herein, we report nitrogen doped CaTiO3 (NCT) perovskite coupled with reduced graphene oxide (RGO), RGO-NCT, composites for the first time and utilize them for environmental remediation as an efficient adsorptive photocatalyst. The adsorption and photocatalytic activity were evaluated by investigating the adsorption/degradation of a model dye, methylene blue (MB). In comparison with bare CT and NCT, the RGO-NCT composites exhibit enhanced photocatalytic activity, which could be attributed to the synergistic effect of the adsorption of dye molecules on the RGO surface followed by their degradation under visible light irradiation. In the degradation mechanism, we propose that the degradation of MB is not only due to the dye photosensitization process but also involves the true photocatalytic action of the RGO-NCT composites. The clear role of graphene as an electron acceptor is demonstrated by photoluminescence spectroscopic study. Also, the degradation of a colorless pollutant thiabendazole (TBZ) under visible light irradiation supports our hypothesis. In addition, the commendable stability and recyclability of RGO-NCT photocatalysts demonstrates that these materials can be used as potential, viable and stable photocatalysts for environmental remediation. In principle, we anticipate that our work paves the way for tailoring the photocatalytic activity of perovskite-type semiconductor materials by coupling with graphene for the design of recyclable bifunctional photocatalysts.