Because the smaller the catalyst particle size, the larger the specific surface area, which promotes the contact between the substrate and oxygen and the catalyst. The radiation under 450 nm and 520 nm wavelengths were used in the reaction. The shorter the wavelength taken, the greater the energy input. Therefore, the conversion rate of the same catalyst under the radiation of 450 nm wavelength is higher than that of 520 nm (Table , entry 2-13). It is interesting that under the same conditions, selfmade TiO2 supported Ni@C catalyst is better than Ni@C/TiO2-5 nm, which is the commercially available TiO2 supported Ni@C.