Catalytic decomposition of H2O2 on Co3O4 doped with MgO and V2O5

The effects of doping of Co3O4with MgO (0.4–6 mol%) and V2O5 (0.20–0.75 mol%) on its surface and catalytic properties were investigated using nitrogen adsorption at −196°C and decomposition of H2O2 at 30–50°C. Pure and doped samples were prepared by thermal decomposition in air at 500–900°C, of pure basic cobalt carbonate and basic carbonate treated with different proportions of magnesium nitrate and ammonium vanadate. The results revealed that, V2O5 doping followed by precalcination at 500–900°C did not much modify the specific surface area of the treated Co3O4 solid. Treatment of Co3O4 with MgO at 500–900°C resulted in a significant increase in the specific surface area of cobaltic oxide. The catalytic activity in H2O2 decomposition, of Co3O4 was found to suffer a considerable increase by treatment with MgO. The maximum increase in the catalytic reaction rate constant (k) measured at 40°C on Co3O4 due to doping with 3 mol% MgO attained 218, 590 and 275% for the catalysts precalcined at 500, 700 and 900°C, respectively. V2O5-doping of Co3O4 brought about a significant progressive decrease in its catalytic activity. The maximum decrease in the reaction rate constant measured at 40°C over the 0.75 mol% V2O5-doped Co3O4 solid attained 68 and 93% for the catalyst samples precalcined at 500 and 900°C, respectively. The doping process did not modify the activation energy of the catalyzed reaction but much modified the concentration of catalytically active constituents without changing their energetic nature. MgO-doping increased the concentration of CO3+–CO2+ ion pairs and created Mg2+–CO3+ ion pairs increasing thus the number of active constituents involved in the catalytic decomposition of H2O2. V2O5-doping exerted an opposite effect via decreasing the number of CO3+–CO2+ ion pairs besides the possible formation of cobalt vanadate.