Efficient photocatalytic CO₂ reduction coupled with selective styrene oxidation over a modified g-C₃N₄/BiOBr composite with high atom economy

Conventional photocatalytic CO₂ reduction is usually combined with the oxidation of H₂O or sacrificial agents, which faces problems such as low catalytic activity and inefficient atom economy. In this work, a photocatalytic CO₂ reduction and selective styrene oxidation synergetic system is developed with an NH₄Cl-modified g-C₃N₄/BiOBr composite photocatalyst. The interfacial heterostructure promotes the formation of surface amino groups and oxygen vacancies, which facilitates the adsorption and chemical reduction of CO₂. The heterostructure also improves the separation of photogenerated electron-hole pairs and enhances the photocatalytic activity. The simultaneous consumption of electrons and holes is beneficial for both CO₂ reduction and styrene oxidation processes. Meanwhile, the oxygen atoms removed during CO₂ reduction are utilized efficiently for styrene oxidation in this synergistic system, and thus the atom economy is improved significantly. The generation rates of CO, CH₄, benzaldehyde and styrene oxide are 802, 8, 684 and 139 μmol g⁻¹ h⁻¹, respectively. This study provides a novel strategy for designing a green photocatalytic CO₂ reduction system.