*2.4. Preparation of Mesosphere TiO2/rGO Sample*

Prepared TiO2 mesospheres (0.2 g) were added to a mixed solution of an equal portion of DI water (15 mL) and ethanol (15 mL) (as solution A). Then, 30 mg of GO powder was dispersed in the same ratio of solvent (DI and ethanol) under stirring for 1 h (as Solution B). Solutions A and B were then mixed with continuous stirring for 1 h. The resultant mixed solution was transferred into a 100 mL autoclave and kept in hot air at 180 ◦C for 12 h. The final product of mesosphere TiO2/rGO was obtained by washing the product with DI water and drying overnight at 60 ◦C.
