γ-Ray-Induced Photocatalytic Activity of Bi-Doped PbS toward Organic Dye Removal under Sunlight

Photocatalysts based on semiconducting chalcogenides due to their adaptable physio-chemical characteristics are attracting attention. In this work, Bi-doped PbS (henceforth PbS:Bi) was prepared using a straightforward chemical precipitation approach, and the influence of γ-irradiation on PbS's photocatalytic ability was investigated. Synthesized samples were confirmed structurally and chemically. Pb_(1-BiS (x = 0, 0.005, 0.01, 0.02) samples that were exposed to gamma rays showed fine-tuning of the optical bandgap for better photocatalytic action beneath visible light. The photocatalytic degradation rate of the irradiated Pb_0.995Bi_0.005S sample was found to be 1.16 times above that of pure PbS. This is due to the occupancy of Bi³⁺ ions at surface lattice sites as a result of their lower concentration in PbS, which effectively increases interface electron transport and the annealing impact of gamma irradiation. Scavenger tests show that holes are active species responsible for deterioration of the methylene blue. The irradiated PbS:Bi demonstrated high stability after being used repeatedly for photocatalytic degradation.