Structural evolution mechanisms of Polydopamine/CdS and photothermal effect boosted photocatalytic H₂ production activity

Polydopamine (PDA) has emerged as a rapidly expanding material that exhibits superior photothermal effect, reducibility, all-purpose adhesive, and chelating abilities. Here, we combine PDA with cadmium sulfide (CdS), a representative semiconductor photocatalyst, to construct a series of nanocomposites displaying unique photothermal activities for H₂ production. By systematically changing the Cd²⁺ dosage, we can get a deep insight into how the chelation between Cd²⁺ and the catechol hydroxyl group affects the morphology, particle size, dispersion state, and surface chemical environment of CdS and PDA nanoparticles (NPs). The synthetic approach also enables us to understand PDA's saturated ability (30.92%±2.31%) in chelating Cd²⁺ and the Cd²⁺ migration, without any loss, in the sulfidation process when depositing the CdS NPs, which has a saturation deposition mass of 32.65%±4.96%, onto the PDA surface. The PDA/CdS nanocomposites exhibit excellent and stable photothermal and photocatalytic behaviors in H₂ production under the xenon lamp irradiation, allowing us to discuss the process and mechanism of the photothermal effect boosted photocatalytic H₂ production activities by changing the irradiation power and the cooling parameters.