The presence of electron withdrawing groups is beneficial to the oxidation of the substrate, and this promoting ability is consistent with the electron withdrawing ability (F->Cl->Br->MeO-). And the electron withdrawing effect in the para position is stronger than that in the meta position. While the existence of the electron-donating group at the ortho position inhibits the oxidation reaction of the substrate, which has almost no effect at the meta position. When there is a methyl group at the meta position, the oxidation reaction of the substrate is not inhibited. This shows that the steric hindrance effect is stronger than Me-(Table ，2 and 6). To differentiate the catalytic activities, microstructures of the Ni@C/TiO2-5 nm and Ni@C/TiO2-Z were studied by TEM. It can be seen from Figure that TiO2 and Ni@C in Ni@C/TiO2-5 nm is not uniformly mixed, while TiO2 and Ni@C in Ni@C/TiO2-Z prepared in situ are uniformly mixed. The distribution of Ti and Ni elements in MAP also provides evidence for the above conclusions. b: UV-Vis absorption spectra of the catalyst. Figure (a) is the XRD diffraction patterns of TiO2-5 nm, TiO2-Z, Ni@C/TiO2-5 nm, and Ni@C/TiO2-Z. The lattice types of TiO2 in these catalysts are the same. The difference is that there are two larger Ni (1 1 1) peaks at 43.3 ° and 44.5 ° in Ni@C/TiO2-5 nm, while Ni@C/TiO2-Z has only two small peaks here. It may be due to uneven dispersion of Ni@C in Ni@C/TiO2-5 nm. In addition, the UV-Vis spectra of TiO2-Z, Ni@C/TiO2-5 nm and Ni@C/TiO2-Z were measured. From Therefore, according to the Kubelka-Munk formula, there is no significant difference in the forbidden band width among them.