Enhancing Solar Light-Driven Photocatalytic Activity of Mesoporous Carbon–TiO2 Hybrid Films via Upconversion Coupling

Solar energy conversion has emerged as an attractive pathway in the decomposition of hazardous organic pollutants. Herein, tridoped β-NaYF4:Yb3+,Tm3+,Gd3+ upconversion (UC) nanorods were embedded in a carbon-doped mesostructured TiO2 hybrid film using triblock copolymer P123 acting as a mesoporous template and carbon source. The photoactivity of our novel material was reflected in the degradation of nitrobenzene, as a representative organic waste. The broad-band absorption of our rationally designed UC nanorod-embedded C-doped TiO2 in the UV to NIR range unveiled a remarkable increase in nitrobenzene degradation (83%) within 3 h compared with pristine TiO2 (50%) upon light irradiation. These results establish for the first time a synergetic bridge between the effects of a creative photon trapping TiO2 architecture, improved NIR light-harvesting efficiency upon UC nanorod incorporation, and a simultaneous decrease in the band gap energy and increased visible light absorption by C-doping of the oxide lattice. The resulting nanostructure was believed to favor efficient charge and energy transfer between the photocatalyst components and to reduce charge recombination. Our novel hybrid nanostructure and its underlined synthesis strategy reflect a promising route to improve solar energy utilization in environmental remediation and in a wide range of photocatalytic applications, e.g., water splitting, CO2 reutilization, and production of fuels.