MnCo₂O₄ Preparation by Microwave-Assisted Route Synthesis (MARS) and the Effect of Carbon Admixture

Abstract

Catalyst spinel MnCo 2 O 4 with particle size <30 nm was prepared by a novel microwave-assisted route. To determine the optimal amount of carbon needed as a microwave susceptor, varying amounts of amorphous carbon powder (7−26 wt %) were mixed with the aqueous solutions of Mn- and Co-nitrates. After heat treatment at 200 °C in a conventional oven, the mixtures were heat-treated in a microwave oven (2.45 GHz) at a power of 350 W. The effect of the carbon amount on the formation and properties of the catalysts was studied. In this production method, 13 wt % of carbon was found to be the minimum needed for spinel MnCo 2 O 4 formation. Most of the carbon was oxidized during the microwave treatment. When the carbon content in the nitrate−carbon mixture was increased beyond 13 wt %, the carbon content and the specific surface area of the final catalyst started to decrease. However, the carbon amount of 18 wt % in the initial nitrate−carbon mixture was found to be the most preferable when considering the catalytic activity of the spinel toward oxygen reduction reaction in alkaline electrolyte.