Catalytic decomposition of H 2O 2 on promoted cobaltic oxide catalysts

Abstract

Pure and ZnO-doped cobaltic oxide catalyst were prepared by thermal decomposition in air at 400–700 °C of pure basic cobalt carbonate and that treated with different amounts of zinc nitrate (0.46–2.25 w% ZnO). X-ray powder diffractometry and BET analysis of nitrogen adsorption isotherms investigated the crystalline bulk structure and the surface area of pure and doped samples, respectively. The hydrogen peroxide decomposition activity was determined by oxygen gasometry of the reaction kinetics at 20–40 °C. The results revealed that the treatment of Co 3O 4 with ZnO at 400–700 °C brought about a significant increase in the specific surface area of cobaltic oxide. However, the catalytic activity of H 2O 2 decompositon on cobaltic oxide calcined at different temperatures was found to show a considerable increase by doping with ZnO. In addition, the catalytic decomposition of H 2O 2 on ZnO-doped cobaltic oxide catalysts required much lower activation energies as compared to that necessary for the reaction on the pure catalysts. The calculated activation energies for the catalytic reaction over both the pure and ZnO-treated catalysts reflected the role of ZnO treatment in modifying the concentration of catalytically active constituents. In other words, the doping process increased the concentration of Co 3+–Co 2+ ion pairs and created Co 3+–Zn 2+ ion pairs increasing thus the number of the active constituents involved in the catalytic decomposition of H 2O 2.