Fabrication And Characteristics Of Electrodeposited MnO₂ On Porous Nickel From Etched Aluminium

Faced with the consumption of resources, human need to find a balance between the use of energy and environmental pollution, new energy storage materials become the world’s mainstream research. As a new energy storage materials, electrochemical capacitors have the obvious advantage such as large energy density value, high charge and discharge rate, Among active electrode materials for supercapacitor, Mn O2 has been thoroughly investigated as a pseudocapacitor due to its high theoretical specific capacitance(SC)(1370 F g-1), relatively low cost and environmental friendliness. However, the capacitance of the thick Mn O2 electrodes is ultimately limited by the poor electrical conductivity of Mn O2. In this paper, a Mn O2 electrode is deposited by anodic electrodeposition on nickel electroformed from etched aluminium. The relationship among the deposition parameters, morphology and electrochemical characteristics of Mn O2/porous nickel electrodes is also discussed.A porous hybrid electrode was fabricated by electrodepositing manganese oxide on porous electroformed nickel from anodized etched aluminium. With increasing deposition current densities, the manganese oxide electrode changed from porous and fibrous to a denser film. The electrochemical characteristics of the Mn O2 electrode are closely related to the mass loading, morphology and scan rate. At the same mass loading, a higher areal and specific capacitance was obtained for Mn O2 film with a denser structure at a higher deposition current density and a low scan rate(for example, 10 m V s-1). A high volumetric capacitance(200 F cm-3) and large areal capacitance(0.9 F cm-2), as calculated from cyclic voltammetry at a scan rate of 1 m V s-1, were obtained for the hybrid electrodes at a deposition current density of 10 m A cm-2 for 10 min. The present hybrid electrodes also showed good cycling stability(almost no reduction after 1000 cycles at a scan rate of 10 m V s-1).Then a Mn O2 electrode was deposited by potentiostatic anodic electrodeposition on nickel electroformed from etched aluminium. We presented different morphology of the controlled deposition of an Mn O2 coating at the surface over a wide range of deposition current density as well as an exploration of the electrochemical behavior of the prepared electrodes. When decreasing the electrodeposition voltage, the morphology of manganese evolved from nanoparticles, nanobeads to nanosheets. Besides, If increasing electrodeposition temperature, the morphology of manganese evolved from nanoparticles to nanosheets,and then from nanorods to nanofiber-clusters. The morphology was affected by the nucleation rate and the relationship between nucleation rate and growth rate during the process of crystal growth. A areal capacitance(0.311 F cm-2), as calculated from cyclic voltammetry at a scan rate of 10 m V s-1, were obtained for the best hybrid electrodes at a deposition voltage of 0.75 V with the electrodeposition temperature of 0 °C,and its morphology was nanobeads.