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

A facile calcination method is developed for the in situ synthesis of nanohybrids of Ti 3+ self‐doped TiO 2 /graphene quantum dot nanosheets (Ti 3+ ‐TiO 2 /GQD NSs). Ti 3+ sites are formed on the surface of the TiO 2 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 rhodamine B (RhB) photodegradation result demonstrates a higher visible‐light photocatalysis performance than that of the original TiO 2 . On one hand, inducing Ti 3+ 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 TiO 2 surface. It is proposed that Ti 3+ sites and GQDs induced in TiO 2 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 Ti 3+ defect sites.