Carbothermal Reduction Induced Ti3+ Self-Doped TiO2/GQD Nanohybrids for High-Performance Visible Light Photocatalysis

A facile calcination method is developed for the insitu synthesis of nanohybrids of Ti3+ self-doped TiO2/graphene quantum dot nanosheets (Ti3+-TiO2/GQD NSs). Ti3+ sites are formed on the surface of the TiO2 nanosheets through carbothermal reduction by GQDs, using citric acid as a carbon source. Such heterojunctions exhibit enhanced visible-light absorption properties, large photocurrent current densities, and low recombination of photoinduced carriers. The methylene blue (MB) and rhodamineB (RhB) photodegradation result demonstrates a higher visible-light photocatalysis performance than that of the original TiO2. On one hand, inducing Ti3+ sites is efficient for the separation of photogenerated charge carriers and for reducing electron-hole pair recombination. On the other hand, GQDs are beneficial for generating more photocurrent carriers and facilitating the charge transfer across the TiO2 surface. It is proposed that Ti3+ sites and GQDs induced in TiO2 nanosheets have a synergistic effect, leading to excellent photocatalysis properties. Finally, a theoretical calculation is provided of the carbothermal reduction for the formation mechanism of the Ti3+ defect sites.