Weigh 120 mg of commercially available TiO2 and 120 mg of Ni@C into 80 ml of ultrapure water, stir at room temperature for 24 h under shading. After centrifugation and washing with ultrapure water, the obtained solid is freeze-dried to obtain Ni@C-TiO2. The commercially available TiO2 used is all anatase TiO2 from Macklin, and the prepared catalyst is named according to the particle size of the TiO2.