| Abstract |
Nanostructured porous MnO2, especially its hydrated amorphous and low crystalline form (MnO2 center dot nH(2)O), has been one of the most promising material considered for charge storage applications, due to electrochemical similarities with RuO2 and its relative low cost. However, the intrinsic poor conductivity of MnO2 combined with the presence of structural water, which provides high ionic but low electronic conductivity, is a great hindrance for wider application. An effective approach to overcome this drawback involves the deposition of thin MnO2 layers on porous, high surface area metallic scaffolds. The present work addresses this route and provides novel insights thanks to the combination of MnOx center dot nH(2)O with custom-made Ni foams, fabricated via one-step electrodeposition using the dynamic hydrogen bubble template (DHBT). The porous Ni foams provide a scaffold with a 3D architecture with optimized pore size and surface. The composite electrode was fabricated by anodic deposition of MnOx center dot nH(2)O on the 3D Ni foams. The electrochemical behaviour was tested in 1M KOH, since there are very few studies addressing the electrochemical behaviour of MnOx center dot nH(2)O in alkaline media for electrochemical supercapacitors applications. In addition, thermal treatment (150-250 degrees C) was performed to evaluate the effect of hydration on the material properties. The results revealed that the as-obtained composites are highly stable, displaying much higher specific capacitances with 73-90\% (depending on the mass load) capacitance retention compared to their de-hydrated counterparts. The charge-discharge processes were found to be highly reversible throughout 5000 cycles, maintaining almost 100\% columbic efficiency. In conclusion, the MnOx center dot nH(2)O@Ni composite electrodes showed a very stable pseudocapacitive behaviour and exceptional cycling performance in 1M KOH, being therefore a promising alternative charge storage electrode for electrochemical supercapacitors. (c) 2018 Elsevier Ltd. All rights reserved. |
