Carbonized Polymer Dots/Bi/β-Bi₂O₃ for Efficient Photosynthesis of H₂O₂ via Redox Dual Pathways

A novel heterojunction photocatalyst of carbonized polymer dots (CPDs)/Bi/β-Bi₂O₃ is successfully synthesized via a one-pot solvothermal method by adjusting the reaction temperature and time. As a solvent and carbon source, ethylene glycol not only supports the conversion of Bi³⁺ to β-Bi₂O₃ but also undergoes its polymerization, cross-linking, and carbonization to produce CPDs. In addition, partial Bi³⁺ is reduced to Bi by ethylene glycol. As a result, the CPDs and Bi are deposited in situ on the surface of β-Bi₂O₃ microspheres. There are four built-in electric fields in the CPDs/Bi/β-Bi₂O₃ system, namely, the n-type semiconductor β-Bi₂O₃/H₂O interface, the p-type CPDs/H₂O interface, the ohmic contact between Bi and β-Bi₂O₃, and the Schottky junction between Bi and CPDs. Under the action of four built-in electric fields, the Z-type charge separation mechanism is formed. It promotes the effective separation of the photogenerated electron-hole and greatly improves the yield of H₂O₂. Under irradiation for 2 h, the H₂O₂ production is 1590 μmol g^-1 h^-1. The solar energy to H₂O₂ conversion efficiency is 0.11%.