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

Abstract We demonstrate appropriate tuning of heterojunctions in CsPbBr x Cl 3−x −MoS 2 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 2 , perovskites with varying halide ratios, various physical mixing ratios of the two, and in‐situ synthesized composite ratios of CsPbBr x Cl 3−x and MoS 2 (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 2 : MoS 2 with a 1 : 2 ratio was observed, removing 98 % of the methylene blue (MB) dye. Notably, only the CsPbBrCl 2 and MoS 2 composite demonstrated higher efficiencies since it resulted in a n‐n type II heterojunction. Additionally, the CsPbBrCl 2 : MoS 2 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 2 : MoS 2 composite, which yielded 265 times more hydrogen than pristine CsPbBrCl 2 . The Faradaic efficiency for 1 : 2 CsPbBrCl 2 : MoS 2 was found to be 96.61 %. Our results offer crucial perspectives on optimizing perovskite‐MoS 2 composites and demonstrate their utility in sustainable applications, including water treatment, renewable energy harvesting, and environmental remediation.