Nitrogen doping-mediated oxygen vacancies enhancing co-catalyst-free solar photocatalytic H2 production activity in anatase TiO2 nanosheet assembly

Introducing oxygen vacancies (Vo) into TiO2 photocatalyst has been considered an effective strategy for improving co-catalyst-free solar photocatalytic activity. However, the methods used to synthesize it require high pressure/temperature and/or hazardous/costly reagents. Here we propose Vo introduction, concomitant with N-doping in TiO2, as an alternative strategy for achieving efficient co-catalyst-free solar photocatalytic activity under less extreme conditions. After calcination at 450 °C of mesoporous spherical assemblies of a layered titanate nanosheet containing N,N-dimethylformamide as its synthesis solvent in the structure, we successfully synthesized mesoporous spherical assemblies of nanosheets composed of anatase TiO2 nanoparticles with Vo mediated by N doping. This material exhibits good co-catalyst-free solar photocatalytic activity for hydrogen evolution via water splitting under irradiation with simulated solar light, which is considerably higher than that of typical co-catalyst-free defective TiO2 materials. We discuss the possible role of the introduced Vo in facilitating charge separation and raising photocatalytic efficiency.