Electrocatalytic Properties of Egg-white Sol-gel Derived MnxFe3-xO4 (0 ≤ x ≤ 1.5) for Alkaline Water Electrolysis

Abstract

Some binary ferrites having molecular formula, MnxFe3-xO4 (0 ≤ x ≤ 1.5) have been synthesized by a simple and cost effective egg white sol-gel route. In each preparation, nitrates of constituent metal were taken as starting materials and egg white as gelling agent. The material, thus obtained was altered in the form of film electrode on the pre-treated Ni- support using an oxide-slurry painting tech-nique and investigated as electrocatalysts for the oxygen evolution reaction in KOH solutions. The study showed that Mn-substitution in the base oxide matrix influences the electrocatalytic activity of the material significantly and found to be greatest with 0.5 mol Mn-substitution. The reaction order has been found to be approximately unity with respect to OH¯ concentration. The Tafel slope values at low potential ranged between ~ 52 and ~ 65 mVdecade-1. The thermodynamic parameters namely, standard apparent electrochemical enthalpy of activa-tion (), standard enthalpy of activation () and standard entropy of activation () for the oxygen evolution reac-tion (OER) have also been determined. It has been observed that and values decreased with Mn-substitution in the Fe3O4 lattice. This decrease inandwas found to be greatest with 0.5 mol Mn. Thevalues were also found to be highly negative varying between ~ - 185 and – 211 J deg-1 mol-1.