Tailoring Heterojunctions in CsPbBrxCl3−x−MoS2 Composites for Efficient Photocatalysis and Hydrogen Evolution

We demonstrate appropriate tuning of heterojunctions in CsPbBr<inf>x</inf>Cl<inf>3−x</inf>−MoS<inf>2</inf> composites (where x=0,1,2,3) by controlled regulation of the halide stoichiometry in the perovskite. A thorough optimization procedure determined the most effective photocatalyst, considering the pristine MoS<inf>2</inf>, perovskites with varying halide ratios, various physical mixing ratios of the two, and in-situ synthesized composite ratios of CsPbBr<inf>x</inf>Cl<inf>3−x</inf> and MoS<inf>2</inf> (2 : 1, 1.5 : 1, 1 : 1, 1 : 1.5, 1 : 2). Under two hours of exposure to visible light, a remarkable photocatalytic performance of CsPbBrCl<inf>2</inf> : MoS<inf>2</inf> with a 1 : 2 ratio was observed, removing 98 % of the methylene blue (MB) dye. Notably, only the CsPbBrCl<inf>2</inf> and MoS<inf>2</inf> composite demonstrated higher efficiencies since it resulted in a n-n type II heterojunction. Additionally, the CsPbBrCl<inf>2</inf> : MoS<inf>2</inf> composite exhibits the highest reaction rate constant, fifteen times higher than the pristine perovskite. Reusability assessment of this combination revealed sustained activity of 87 % for up to 5 cycles. The hydrogen evolution reaction investigations were carried out using the optimized CsPbBrCl<inf>2</inf> : MoS<inf>2</inf> composite, which yielded 265 times more hydrogen than pristine CsPbBrCl<inf>2</inf>. The Faradaic efficiency for 1 : 2 CsPbBrCl<inf>2</inf> : MoS<inf>2</inf> was found to be 96.61 %. Our results offer crucial perspectives on optimizing perovskite-MoS<inf>2</inf> composites and demonstrate their utility in sustainable applications, including water treatment, renewable energy harvesting, and environmental remediation.