“Abstract” In this research, cobalt oxide solid solution nanoparticles with molar percentages of zinc content (2.5, 5, 7.5, 10, 15, 20, 30 mol %) were synthesized by hydrothermal method. Cobalt nitrate and zinc nitrate have been used as sources of cobalt oxide and zinc content. In order to investigate the structural properties, chemical state, optical, photocatalytic properties and microstructure of the synthesized nanoparticles were characterized by XRD, BET-BJH, UV-Vis, XPS, TEM and FESEM analyzes. The results of X-ray phase analysis showed that the addition of content in the structure of cobalt oxide led to a decrease in crystal size. The crystallite size of the pure sample was about 9.48 nm and the doped sample was about 8.8 nm. According to the FESEM images, the particle size of the pure sample was in the range of 20-40 nm and the doped ZCH-300 sample (10%Zn) was in the range of 20-30 nm. The specific surface area (BET) of the pure sample was about 75 m2/g and the sample with 10% zinc was about 92 m2/g. Doped Co3O4 (CH) mesoporous nanoparticles were shown to have highest photocatalytic activity as compared with the pure CH nanoparticles. The photocatalytic analysis results showed that the highest percentage of degradation of the solution was obtained in the presence of the doped sample with zinc cation (10%Zn) equal to 10.6 (η(ZCH-300) = 10.6%).
