ELECTROCATALYSTS BASED ON Ni-, Co-SPINELS

Abstract

The synthesis of Ni-, Co-spinels was performed using coprecipitation method with precursors Ni and Co nitrates under different conditions: using precipitators NaOH and NH4OH, at different pH values and different aging durations.Structural, adsorption and catalytic properties by of Ni-, Co-spinels were determined by X-ray diffraction, desiccator method of adsorption of benzene vapor and in redox reactionof hydrogen peroxide decomposition. The size of the crystallites of obtained spinels was calculated from X-ray diffraction patterns and all of the samples were nano-dispersed with developed surface area from 92 to 320 m2/g. Electrocatalytic investigations have shown thatthe most active spinels were obtained by precipitation with NH4OH at pH 9,0. The highest catalytic activity from all of the twelve spinels samples in hydrogen peroxide decomposition reaction had Ni-, Co-spinel, precipitated by NH4OH at pH 9,0 and aged for 3 days whichshown 100% decomposition degree of H2O2 after 45 seconds of contact.According to the results, the conditions of synthesis of Ni-, Co-spinels highly effect on their catalytic activity. Significantly lower catalytic activity of samples precipitated by NaOH, in our opinion, explained by the inhibitory effect of sodium, which is formed by the heat treatment of samples containing NaOH in trace amounts. Established that with decreasing pH values to neutral the activity of Ni-, Co-spinels increases and with increasing durationof aging of samples their catalytic activity is reduced due to the recrystallization process sediment, resulting in the number of active sites on the surface of Ni-, Co-spinels decreases.