Selective CO production via a dual-defective CdS/BiOCl photocatalyst for CO2 photoreduction

Abstract

Designing a novel and highly selective photocatalyst for CO₂ photoreduction is of great significance but remains challenging due to problems such as the high recombination rate of photogenerated carriers and the weak reactivity of photocatalyst surfaces. Herein, a dual-defective S-scheme heterostructure of BiOCl with oxygen vacancies and CdS with sulfur vacancies (OV-B/SV-C) was constructed by a two-step solvothermal method. The as-prepared dual-defective composite not only exhibits the maximum CO evolution rate of 272 μL g⁻¹ h⁻¹ without any hole-sacrificing agents and high selectivity for CO evolution (97%), but also shows an excellent Cr(VI) photoreduction performance within 60 s. Experimental characterization and DFT results indicate that dual-defective introduction can not only stabilize *COOH intermediates but also decrease the energy barrier of intermediates during the CO₂ photoreduction process. In the meantime, forming an S-scheme greatly accelerates the charge transfer between OV-B and SV-C and maintains strong redox capacities for the CO₂ photoreduction reaction. The high selectivity and activity of the dual-defective OV-B/SV-C sample mainly originate from the introduction of oxygen and sulfur vacancies in the CdS/BiOCl and construction of the S-scheme heterostructure. This work paves a promising way for tuning photocatalytic activities and selectivities by constructing a dual-defective S-scheme heterostructure.