Microwave irradiated Ni–MnOx/C as an electrocatalyst for methanol oxidation in KOH solution for fuel cell application

Abstract

Ni–MnOx/C electrocatalyst was synthesized by the reduction of nickel precursor salt on MnOx/C powder using NaBH4 and the deposition process was motivated with the aid of microwave irradiation. Finer nickel nanoparticles were detected in Ni–MnOx/C using transmission electron microscopy with a lower particle size of 4.5nm compared to 6nm in Ni/C. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS) were applied to study the electrocatalytic activity of Ni–MnOx/C for methanol oxidation in 0.5M KOH solution. The presence of 7.5wt.% MnOx in Ni–MnOx/C enhanced the oxidation current density by 1.43 times. The catalytic rate constant of methanol oxidation at Ni–MnOx/C was calculated as 3.26×103cm3mol−1s−1. An appreciable shift in the maximum frequency at the transition from the resistive to capacitive regions to a higher value in Bode plots of Ni–MnOx/C was shown when compared to Ni/C. It was accompanied by lowered phase angle values. The lowered Warburg impedance value (W) of Ni–MnOx/C at 400mV confirmed the faster methanol diffusion rate at its surface.