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 TiO 2 hollow microspheres in large scale. The as-prepared hollow spherical TiO 2 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 TiO 2 hollow microsphere catalyst demonstrates much higher photocatalytic activity toward photodriven reduction of CO 2 with H 2 O into CH 4 compared with the state-of-the-art photocatalyst, commercial Degussa P25 TiO 2 . Also, the simple synthesis strategy would enable large-scale industrial production of CuO–TiO 2 hollow microspheres.