Macroporous MnO2 electrodes obtained by template assisted electrodeposition for electrochemical capacitors

Abstract

Eletrodos macroporosos de MnO 2 foram preparados por eletrodeposição assistida por molde de partículas esféricas coloidais de poliestireno. A molhabilidade desses filmes foi estudada por medidas de ângulo de contato. Medidas de voltametria cíclica foram realizadas com o objetivo de estudar o seu comportamento como eletrodo para supercapacitores. A capacitância específica obtida foi cerca de 60% maior que a obtida por um eletrodo liso, o que mostra que apesar de a molhabilidade do eletrodo macroporoso ser menor, ocorre alguma penetração do eletrólito pelos poros, aumentando a área eletroativa. Por fim, o eletrodo macroporoso apresentou excelente establidade eletroquímica, não sendo observada queda de capacitância após 1000 ciclos de carga e descarga.Macroporous MnO 2 electrodes prepared by template-assisted electrodeposition using spherical polystyrene colloidal particles are studied. The wettability of such electrodes by a LiClO 4 aqueous electrolyte is measured by the contact angle technique. Cyclic voltammetry experiments are performed in order to evaluate the use of these electrodes for electrochemical capacitor applications. The specific capacity obtained is about 60% higher than that obtained for flat MnO 2 surfaces showing that, in spite of the wettability being lower, some penetration of the electrolyte into the pores must occur, increasing the electroactive area with respect to the flat electrode. Furthermore, the macroporous electrode showed excellent electrochemical stability, with neither a capacitance decrease nor a loss of morphology, after 1000 cycles.Keywords: supercapacitors, manganese oxide, porous electrodes, template assisted electro deposition, wettability IntroductionLi-ion batteries are widely used as energy sources for portable electronic devices, and several studies have been carried out in order to improve their performance.1 As charge/discharge processes are limited by reaction kinetics, 2 the search for devices that can deliver high power is an active field. Electrochemical capacitors or supercapacitors are high power sources that can be fully charged/discharged in seconds because they are based on surface faradaic reactions and/or double-layer capacitance.3,4 These devices can be applied together with a battery in order to allow both high energy and power or to replace conventional capacitors based on electrical charge separation. The preparation of high surface area electrodes can improve device performance because more material is available on the surface for charge compensation as well as for energy storage. 2Concerning redox-active materials for supercapacitors, RuO 2 presents the best capacitance values. However, its high cost does not allow its use in practical applications. 5 An alternative low cost, non toxic and environmentally friend material is MnO 2 .6-9 The electrochemical performance of MnO 2 -based supercapacitors and the mechanism of energy storage depend on several aspects, such as morphology, 10,11 structure 12,13 and post synthesis thermal treatment. 14 The major in...

The effects of Fe-doping on MnO2: phase transitions, defect structures and its influence on electrical properties

“…In order to enhance the properties, up until now, various synthesis methods have been developed, namely sol–gel, 10 co-precipitation, 11 electrodeposition, 12 and hydrothermal reaction. 13 These various methods are able to reduce the crystal size, enlarge the surface area for the enhancement of the ion diffusion rate 8 and finally improve the supercapacitive performance of MnO 2 .…”

Nanostructured Manganese oxide Films for High performance Supercapacitors

“…Manganese oxide arrays composed of vertically aligned nanotubes/nanowires have been fabricated by using anodic aluminum oxide (AAO) templates, showing superior capacitive performances [22][23][24][25][26][27]. Mesoporous manganese oxide films have also been reported and improved capacitive performances were achieved [28][29][30][31][32][33]. However, the relatively high fabrication cost of the template methods and the environmentally unfriendly nature of the template removal process are two major obstacles to their commercial application.…”

Nickel-Copper Alloys Modified Electrodes: an Electrochemical Study on their Interfacial and Supercapacitive Properties

“…26 Macroporous manganese oxide electrodes were prepared by template-assisted electrodeposition showing specific capacitance 60% higher than that obtained from flat surfaces, without loss of capacitance even after 1000 cycles. 27 In addition, Tsai et al 28 reported the influence of the electrodeposition method on the morphology and capacitive properties of the electrodes. In this work, it was described the preparation of composites based on MnO 2 /Ni foams by three different methods: potentiodynamic (PD), potentiostatic (PS) and a combination of them (PS + PD ) and long cycle life.…”

“…27 In addition, Tsai et al 28 reported the influence of the electrodeposition method on the morphology and capacitive properties of the electrodes. In this work, it was described the preparation of composites based on MnO 2 /Ni foams by three different methods: potentiodynamic (PD), potentiostatic (PS) and a combination of them (PS + PD).…”