Hierarchical CuO-TiO2 Hollow Microspheres for Highly Efficient Photodriven Reduction of CO2 to CH4

In this study, a scalable one-pot template-free synthesis strategy was employed to fabricate CuO-incorporated TiO2 hollow microspheres in large scale. The as-prepared hollow spherical TiO2 nanoparticles possess unique structural characteristics, namely, large surface area and a hierarchical nanoarchitecture composed of a hollow macroporous core connected with large mesopores in the shell. The large surface area provides a great number of surface active sites for the reactant adsorption and reaction whereas the hierarchical nanoarchitecture enables fast mass transport of reactant and product molecules within the porous framework. In addition, the hollow macroporous core-mesoporous shell nanostructure favors multilight scattering/reflection, resulting in enhanced harvesting of exciting light. Furthermore, the incorporated CuO clusters work efficiently as a cocatalyst to improve the photocatalytic activity. As a result, the CuO-incorporated TiO2 hollow microsphere catalyst demonstrates much higher photocatalytic activity toward photodriven reduction of CO2 with H2O into CH4 compared with the state-of-the-art photocatalyst, commercial Degussa P25 TiO2. Also, the simple synthesis strategy would enable large-scale industrial production of CuO-TiO2 hollow microspheres.