Graphite Carbon Nitride Accelerating Interfacial Electron Transfer of Defect-Rich TiO2 for N2 Photofixation

The photocatalytic N2 fixation reaction still faces high N2 activation energy barriers and inefficient electron transfer efficiency, limiting the overall ammonia yield of semiconductors. This communication reports on the construction of an organic/inorganic g-C3N4/oxygen vacancy-enriched TiO2 (g-C3N4/TiO2-OV) composite system via the annealing treatment in an H2/Ar mixed atmosphere for enhanced photocatalytic N2 fixation activity. After illumination for 4 h, g-C3N4/TiO2-OV with 1 wt% g-C3N4 loading demonstrates the optimal ammonia yield of 31.6 μmol L−1. This study demonstrates the existence of oxygen vacancies on the TiO2 surface through EPR while also investigating the carrier separation and transport efficiency of the material using photoelectric characterization. The experimental results indicate that the introduction of OVs into TiO2 serves as Lewis acid sites, facilitating N2 adsorption. Moreover, the lower onset potential and higher current density of g-C3N4/TiO2-OV composites indicate that the construction of the heterojunction composite significantly decreases the interfacial charge recombination and N2 activation energy barrier, effectively improving the ammonia yield towards N2 photo-reduction. This work emphasizes the importance of rational tailoring of TiO2-based photocatalysts in the field of N2 fixation.