Insights into enhancing photocatalytic reduction of CO2: Substitutional defect strategy of modified g-C3N4 by experimental and theoretical calculation approaches

The defects in g-C3N4 by material substitution have been proven to enhance photocatalytic reaction. Even so, accurate position substitution of carbon doping for defects in g-C3N4 structure remains a significant challenge. Herein, we investigate the effects of C/doping on the optical and electronic structure of g-C3N4 by combining experiments and density functional theory (DFT). The results reveal that substitution of C atom with N site by 12.7% defect concentration confer efficient separation of electron-hole pairs and photo-catalytic activity in comparison with the pristine g-C3N4. The defect constructed at C-N1 site position exhibits expanded light absorption edge of g-C3N4, and indicates a small bandgap while maintaining a negative value of CB potential for CO2 reduction to methanol. During performance testing, the highest methanol yield of 651.7 mu mol gcat(-1) h(-1) and AQY = 0.019 with ca. 40% improvement are reported over 0.2C/g-C3N4 compared to pristine g-C3N4. First principle calculations attest the defect position of g-C3N4 structure, introduced by carbon dopant, is beneficial as a tuneable energy band gap that increases light harvesting. This work highlights defect engineering of g-C3N4 structure by carbon doping is a promising way to enhance the performance of photocatalytic carbon dioxide reduction to methanol. (C) 2021 Elsevier B.V. All rights reserved.