Synthesis, Characterization and Pseudocapacitive Behaviour of MnO x /CNT Heterostructures
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Synthesis, Characterization and Pseudocapacitive Behaviour of MnOx/CNT Heterostructures Chung-Ying Tsai1, Kanchan Mondal1, *, S. Talapatra2 1
Department of Mechanical Engineering and Energy Processes, Southern Illinois University, Carbondale, IL\ 2 Department of Physics, Southern Illinois University, Carbondale, IL * corresponding author – [email protected] ABSTRACT Manganese oxide based nanoparticles were synthesized by sol-gel process. Methanol, ethanol, and propanol were used as alternative solvent during sol-gel process with manganese acetate as precursor for the preparation of pristine manganese oxide. Hybrid MnOx modified by additions of carbon nanotubes was further prepared. Smallest particle size was observed for manganese oxide prepared from propanol, with diameters range from 16 nm to 50nm. XRD results showed that the as prepared manganese oxide based samples at calcination temperature of 300ºC and above were composed of Mn2O3 as dominant phase, with Mn3O4 as minor phase. Specific capacitance measured from two electrode systems of manganese oxide prepared from methanol, ethanol, and propanol at scan rate of 10 mV/s were 88.3, 66.0, 104.8 F/g and the result for the hybrid sample was 140.5 F/g. The highest capacitance of the MnOx revealed a specific capacitance of 231.4 F/g when a 1:1 mixture of propanaol and methanol was employed as the solvent for the sol preparation. Results from electrochemical impedance spectroscopy (EIS) also showed superior electrochemical properties of the hybrid sample over pristine manganese oxide samples. Key words: Manganese oxide, CNT, sol-gel process, supercapacitor, Ragone plot INTRODUCTION Supercapacitor utilizes the electrochemical reaction at the electrode to store energy. These devices exhibit similar power density as conventional capacitors but comparatively have higher specific capacitance and thus higher energy density to values closer to those of conventional batteries [1, 2]. In other words, supercapacitors fill the void between batteries and conventional dielectric capacitors in Ragone plots [3]. Metal oxides such as RuO2 [4], MnOx [2], and Fe3O4 [5] and conducting polymers are often used as the electrode material. Ruthenium oxide exhibit superior specific capacitance (up to 1340F/g [4]), but is too expensive to be commercialized. Manganese oxide, on the other hand, has the advantage of low cost of the material and multiple oxidation states. In addition, its low toxicity also makes it more amenable for commercialization [2]. As a result, manganese oxide has been extensively investigated for use as electrode material for supercapacitors over the last decade. However, manganese oxide suffers from lack of metallic conductivity [2] and thus unable to achieve its theoretical capacitance values as often seen in ruthenium oxide based supercapacitors. Hence, much of the effort had been directed towards improving the capacitance of manganese oxide by different techniques such as addition of secondary element to the manganese oxide material.
In this research, synthesis of man
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