Tailoring Novel SnO2/α-MnO2 Composites for Photocatalytic Performance Under Visible-Light

Efficient removal of industrial effluents from wastewater is critical for a clean and sustainable water supply. In this study, novel nanosized SnO2/MnO2 photocatalysts with crystallite size between 34-40 nm were synthesized and evaluated for methylene blue (MB) degradation under visible light. The optimal percentage of MnO2 nanowires was explored for superior photocatalytic efficiency by varying its amount in the composites. The findings suggested that the SnO2/MnO2 composites exhibited enhanced photocatalytic performance compared to their individual components, which was attributed to the synergistic interaction between SnO2 and MnO2. Preliminary analysis by X-ray diffraction, Raman spectra, and EDX confirmed the crystalline structure and chemical composition of SnO2, MnO2 and their composites. Additionally, the morphology of MnO2 was observed to be of nanowires; while SnO2 was found to be comprised of agglomerated particles. Notably, the photocatalysts demonstrated a systematic reduction in the bandgap of the composites with increasing MnO2 content, leading to improved visible light utilization. Among all the prepared photocatalysts, the optimized SnO2/MnO2 composite with 75 wt. % MnO2 (denote as SM-3) revealed exceptional photocatalytic activity by degrading 93% of MB in 150 min of light exposure. Moreover, the catalytic process followed pseudo-first-order kinetics, highlighting the efficiency of the composites. The scavenger studies suggested that holes, hydroxyl and superoxide radicals are primarily responsible for the MB degradation. The composite SM-3 also exhibited impressive stability and reusability. This study demonstrates the potential of SnO2/MnO2 composites as effective photocatalysts for wastewater treatment under visible light.