Borate functionalization-regulated band structure overcomes the limitations of In2S3 in efficient and selective light-driven CO2-to-CO conversion

Abstract

Photocatalytic conversion of carbon dioxide (CO₂) into valuable chemical and fuel products is a potentially effective pathway to mitigate the continuous increment of CO₂ concentrations in the atmosphere. Nevertheless, the insufficient conversion efficiency and product selectivity of the photocatalytic reaction remain serious obstacles that restrict its future and practical commercialization. Herein, a borate-functionalized In₂S₃ nanosheet catalyst is successfully synthesized for the first time via a boric acid (BA)-assisted solvothermal method and demonstrated to exhibit highly efficient and selective photocatalytic CO₂ conversion. This synthetic approach not only decorated the catalyst surface with borate functional groups but also engineered the energy band structure of In₂S₃, overcoming the limitations of In₂S₃-based materials in photocatalysis. Accordingly, the optimum photocatalyst (i.e., BIS-3) has exceptional CO₂ conversion efficiency (28 µmol g⁻¹ h⁻¹ and 0.8 µmol g⁻¹ h⁻¹ for CO and CH₄, respectively) with 89.2% selectivity toward CO production, which is the highest record among reported phase-pure In₂S₃ and metal sulfide photocatalysts without the utilization of sacrificial agents. Moreover, the fabricated catalyst achieved high stability and excellent recyclability. This remarkable performance is attributed to the enhanced charge carrier generation/separation, as well as the optimal redox efficiency provided by the borate functionalization-induced energy band structure engineering. In addition, theoretical simulations demonstrated that the borate-rich surface is favorable for excellent CO₂ adsorption and facile CO desorption. This work offers a facile method for rationally functionalizing photocatalysts and electronically engineering the band structure, opening avenues for developing the efficiency, selectivity, and stability of metal sulfides in the light-driven CO₂ conversion field.