Construction of S-scheme PDA/BiPO4 heterojunctions: synergizing photothermal effects and enhanced charge separation for highly efficient photocatalytic degradation

To solve the problems of narrow light absorption range and relatively fast photogenerated carrier recombination of traditional photocatalysts, this paper synthesizes a new core-shell polydopamine/bismuth phosphate (PDA/BiPO 4 ) composite material, which has an S-scheme heterojunction structure. The two – step solvothermal method is adopted, and then in-situ self-polymerization of dopamine is carried out. Adding polydopamine (PDA) not only broadens the light response range of the material but also greatly improves photothermal conversion efficiency. The experimental results demonstrated that the optimized 10% PDA/BiPO 4 composite achieved a degradation efficiency of 92% for Methylene Blue (MB) in 150 min under simulated solar irradiation. The kinetic rate constant (0.01612 min −1 ) was approximately 7 times that of pure BiPO 4 . The wide light absorption of PDA and the S-scheme heterojunction make the composite material have excellent photothermal properties, and the surface temperature rises to 108.3 °C within 120 s. Mechanism analysis shows that the S-scheme charge transfer pathway suppresses the recombination of electron-hole pairs, and the synergistic photothermal effect accelerates the interface catalysis. This study provides a multifunctional strategy integrating enhanced light absorption, efficient charge separation, and photothermal conversion, and provides new insights for designing high-performance full-spectrum responsive photocatalysts.