Built-in electric field and interfacial orbital coupling of Z-scheme CPDs/Bi₃O₄Cl for boosted CO₂ photoreduction

Photocatalytic CO₂ reduction faces many challenges including rapid charge recombination and inefficient charge transfer. We construct a 0D/2D Z-scheme heterojunction of carbonized polymer dots and Bi₃O₄Cl nanosheets (CPDs/Bi₃O₄Cl). This structure enables efficient carrier separation while maintaining the strong redox potentials of both components. Without sacrificial agents, the 7 wt% CPDs/Bi₃O₄Cl composite achieves a CO production rate of 11.17 μmol g⁻¹·h⁻¹, 2.9 times that of pure Bi₃O₄Cl. DFT calculations show interfacial charge redistribution generates an internal electric field, directing charge transfer, suppressing recombination, and enhancing CO₂ adsorption. The elongated C–O bonds and robust C 2p-Bi 6p orbital interactions directly evidence efficient CO₂ activation at the interface. These effects lower the energy barrier for *COOH formation from 1.32 to 0.78 eV, highlighting the role of carbon dots and interfacial orbital coupling in Z-scheme photocatalysts for enhanced adsorption-activation. © 2026 American Institute of Chemical Engineers.