Surface engineering of hollow carbon nitride microspheres for efficient photoredox catalysis

Photocatalysis has attracted extensive interests because of the potential applications in remedying emerging contaminants and easing ever-increasing energy crisis. Towards practical applications of photocatalysis, exploring competing semiconductor materials is a critical challenge. Herein, hollow carbon nitride microspheres (HCNMS) were synthesized via a template-free hydrothermal approach, in which -OH groups (OH-HCNMS) were used for further tuning the surface features. Their properties were thoroughly investigated by a number of advanced characterization methods. The as-prepared HCNMS achieved an impressive p-hydroxybenzoic acid (HBA) degradation rate of 0.013 min(-1), which was 4.3 times higher than pristine carbon nitride (C3N4), even higher than some heterostructured or noble metal modified C3N4. The enhanced photooxidation activity of HCNMS was achieved because of the optimized band structure and the deepened valence band edge, as unveiled by both experimental and density functional theory (DFT) calculation results. In addition, OH-HCNMS exhibited an apparent quantum efficiency (AQE) of 3.7% at 420 nm. The improved hydrogen efficiency of OH-HCNMS was ascribed to the surface functionalized -OH groups, which react with holes, and release more electrons to participate the water splitting, as well as the modified orbital configuration which facilitates the faster charge carrier transfer.