Effects of manganese nitrate concentration on the performance of an aluminum substrate β-PbO2-MnO2-WC-ZrO2 composite electrode material

An Al/conductive coating/alpha-PbO2-CeO2-TiO2/beta-PbO2-MnO2-WC-ZrO2 composite electrode material was prepared through electrochemical oxidation co-deposition on an Al/ conductive coating/alpha-PbO2-CeO2-TiO2 substrate. The effects of manganese nitrate concentration on the chemical composition, electrocatalytic activity, and stability of the composite anode material were investigated using energy dispersive X-ray spectroscopy, anode polarization curves, quasi-stationary polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray diffraction. Results revealed that the WC and nano-ZrO2 content in the beta-PbO2-MnO2-WC-ZrO2 composite coatings increased with increasing manganese nitrate concentration. Moreover, the highest values of 6.61 wt% and 3.51 wt%, respectively, were achieved at 80 g L-1 manganese nitrate. PbO2 content decreased and MnO2 content increased with the increasing manganese nitrate concentration; both the descending and ascending trends were nonlinear. The Al/ conductive coating/alpha-PbO2-CeO2-TiO2/beta-PbO2-MnO2-WC-ZrO2 composite electrode obtained at 80 g L (1) manganese nitrate concentration in plating solution exhibited reduced overpotential for oxygen evolution (0.610 V at 500 A m(-1), highest electrocatalytic activity, longest service life (360 h at 40 degrees C in 150 g L-1 H2SO4 solution at 2 A cm(-2)), and lowest cell voltage (2.75 V at 500 A m(-2)). Furthermore, the composite coating obtained with 80 g L-1 manganese nitrate had uniform crystal grains. The deposit formed was flat, dense, and crackless. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.