SmMnO3-decorated ZnO in a hexane-water interface for enhancing visible light-driven photocatalytic degradation of malachite green.

Malachite green (MG) contributes to water contamination because its accumulation adversely impacts aquatic systems. For the first time, we prepare a high photoresponse of ZnO/SmMnO3 heterojunction via a high-speed stirring method at the nonpolar-polar interface assisted by Alstonia scholaris leaves extract (ASLE) as natural hydrolyzing and stabilizing agents. The heterojunction formation boosts the photocatalytic activity of ZnO up to 91.74% under visible light irradiation. Photoluminescence analysis confirmed that modification with SmMnO3 increases the separation of photogenerated charges and plummets the recombination rates of electron-holes, which induces high photodegradation of MG. With 3 mg of catalyst, the %TOC removal efficiency for MG degradation over ZnO/SmMnO3 was found to be 53.09%, which is higher than that over ZnO. The kinetics model for the photocatalytic reaction was a pseudo-first-order with excellent stability in four consecutive cycles with no structural change. The radical trapping experiment suggests that h+ was the major species in the MG photodegradation reaction. Additionally, morphology and elemental analyses clearly present the formation of ZnO/SmMnO3 heterojunction without any impurities. The current research demonstrates a simple and advanced technique to design heterojunction photocatalyst at the interface of hexane-water.