Electrochemical Performance of Cu Nanoparticle/Carbonized Wood Electrode for Supercapacitor Application
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Electrochemical Performance of Cu Nanoparticle/Carbonized Wood Electrode for Supercapacitor Application
Shiang Teng and Ashutosh Tiwari Nanostructured Materials Research Laboratory, Department of Materials Science and Engineering, University of Utah
ABSTRACT The electrochemical effects of embedding Cu nanoparticles in carbonized wood supercapacitor electrodes have been investigated. The nanoparticles were embedded using a solution method. Subsequent X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the Cu nanoparticles were anchored uniformly on the surface and deep within the pores of the electrode. Cyclic voltammetry measurements showed that the electrode has typical pseudocapacitive behavior, with two pairs of redox reaction peaks. The charge-discharge cycling also indicated that the redox charge transformation was a reversible process. An ultrahigh specific capacitance of 888 F/g and an energy density of 123 Wh/kg were observed for the Cu loaded electrodes, as compared to the pure carbonized wood electrodes, which had a specific capacitance of 282 F/g and an energy density of 39 Wh/kg. Furthermore, both the carbonized wood and Cu loaded electrodes exhibited excellent long cycle abilities with at least 95% of the specific capacitance retained after 2000 cycles. These remarkable results demonstrate the potential for using Cu nanoparticle loaded carbonized wood as a high performance and environmentally friendly supercapacitor electrode material. INTRODUCTION The crisis of fossil fuel depletion and concerns regarding their environmental impacts have motivated research on the low cost and environmentally friendly energy storage systems. These include secondary Li ion batteries and supercapacitors, which are expected to fulfill the needs of modern society [1]. Supercapacitors are expected to dominate future applications, as they are able to store and deliver energy at relatively high rates as compared to Li ion batteries. Supercapacitors store the charge electrostatically through two energy storage mechanisms – electrical double layer (EDL) formation and pseudocapacitive charge storage. EDL formation is simply the separation of charge at the interface between the electrode and the electrolyte, while the pseudocapacitive charge storage mechanism generates charges through rapidly occurring redox reactions. Electrode materials such as carbon based materials, metal oxides, and conducting polymers have been heavily investigated for supercapacitors [2-4]. Among these, different carbon based materials such as carbon nanotubes (CNT), graphene, and high surface area activated carbon have been shown to exhibit moderate specific capacitance values [5-8]. On the other hand,
supercapacitors based on metal oxides such as RuO2, MnO2, and CuO have been reported to have high specific capacitance values due to their fast faradic redox reactions [3, 9-11]. Nevertheless, their applications are limited, due to the high resistance between the electrode materials and the current collectors. Other materia
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