Enhancing CO2 photoreduction by construction of g-C3N4/Co-MOFs S-scheme heterojunction

Abstract

The Co-MOFs/g-C 3 N 4 S-scheme heterojunction shows enhanced CO 2 photoreduction with CO production rate of 16.1 μmol g −1 h −1 , which is 4.7 times that of pure g-C 3 N 4 . The improved light absorption and steered charge separation and migration in S-scheme heterojunction play substantial roles in enhancing activity. • S-scheme heterojunction was developed by combining the Co-MOFs with g-C 3 N 4 . • The contact between Co-MOFs and g-C 3 N 4 enhances charge separation and transfer. • In situ XPS, EPR, and DFT validate the S-scheme heterojunction. The photocatalytic conversion of carbon dioxide (CO 2 ) into valuable products holds great promise from environmental and economic perspectives. However, current photocatalytic materials still exhibit unsatisfactory efficiency. In this study, a notably efficient step-scheme (S-scheme) heterojunction was developed by combining the Co-MOFs with carbon nitride nanosheets (g-C 3 N 4 ). The electrostatic interaction between these components not only facilitates the exfoliation of g-C 3 N 4 layers but also enhances the stability of the photocatalyst structure. The optimal heterojunction Co-CN4 photocatalyst achieved a significantly enhanced CO production rate of 16.1 µmol g −1 h −1 , which is 4.7 times higher than that of pure g-C 3 N 4 . This improved activity is ascribed to the enhanced light absorption and mitigated charge carrier recombination. Density functional theory (DFT) computations in conjunction with experimental observations elucidate the establishment of a close contact interface. Additionally, electron paramagnetic resonance (EPR) and in situ X-ray photoelectron spectroscopy (XPS) characterization unveil the electron transfer pathway of Co-CN4 during photocatalytic CO 2 conversion. This study offers valuable insights into the design of S-scheme photocatalysts for enhancement of CO 2 photoreduction.