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

An Al/conductive coating/α-PbO2–CeO2–TiO2/β-PbO2–MnO2–WC–ZrO2 composite electrode material was prepared through electrochemical oxidation co-deposition on an Al/conductive coating/α-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 β-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/α-PbO2–CeO2–TiO2/β-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−2), highest electrocatalytic activity, longest service life (360 h at 40 °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.