Hierarchical Porous O‐Doped g‐C₃N₄ with Enhanced Photocatalytic CO₂ Reduction Activity

Abstract

Artificial photosynthesis of hydrocarbon fuels by utilizing solar energy and CO 2 is considered as a potential route for solving ever‐increasing energy crisis and greenhouse effect. Herein, hierarchical porous O‐doped graphitic carbon nitride (g‐C 3 N 4 ) nanotubes (OCN‐Tube) are prepared via successive thermal oxidation exfoliation and curling‐condensation of bulk g‐C 3 N 4 . The as‐prepared OCN‐Tube exhibits hierarchically porous structures, which consist of interconnected multiwalled nanotubes with uniform diameters of 20–30 nm. The hierarchical OCN‐Tube shows excellent photocatalytic CO 2 reduction performance under visible light, with methanol evolution rate of 0.88 µmol g −1 h −1 , which is five times higher than bulk g‐C 3 N 4 (0.17 µmol g −1 h −1 ). The enhanced photocatalytic activity of OCN‐Tube is ascribed to the hierarchical nanotube structure and O‐doping effect. The hierarchical nanotube structure endows OCN‐Tube with higher specific surface area, greater light utilization efficiency, and improved molecular diffusion kinetics, due to the more exposed active edges and multiple light reflection/scattering channels. The O‐doping optimizes the band structure of g‐C 3 N 4 , resulting in narrower bandgap, greater CO 2 affinity, and uptake capacity as well as higher separation efficiency of photogenerated charge carriers. This work provides a novel strategy to design hierarchical g‐C 3 N 4 nanostructures, which can be used as promising photocatalyst for solar energy conversion.