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Manufacture of metal oxide electrodes: Thermochemical oxide layers, metal oxide hydrates, amorphous and crystalline powders, and supported and adsorbed ruthenium di-oxide (RuO2). | Electrochemical Metal Oxides Capacitors P Kurzweil University of Applied Sciences Amberg Germany 2009 Elsevier B.V. All rights reserved. This article outlines 1 . Redox processes at metal oxides Pseudocapacitance of ruthenium oxide mixed metal oxides and nonprecious metals. 2. Manufacture of metal oxide electrodes Thermochemical oxide layers metal oxide hydrates amorphous and crystalline powders and supported and adsorbed ruthenium di-oxide RuO2 . 3. Operating behavior of metal oxide supercapacitors Frequency response voltage dependence of capacitance temperature dependence short-circuit power and cycle life self-discharge and aging. 4. Practical embodiments and patent survey. Redox Processes at Platinum Metal Oxides Precious metal oxides are well known for their high specific capacitance low resistance and excellent longterm stability. Since the late 1 970s ruthenium dioxide coated on titanium supports has been developed as a highly active material for dimensionally stable electrodes DSEs for chloralkali electrolysis. In recent years high-surface-area carbon materials have been used as substrates for finely dispersed platinum metal oxides. Pseudocapacitance of RuO2 and IrO2 At room temperature ruthenium dioxide and iridium dioxide are mixed electronic and ionic conductors having conductivities of 25 000 and 22 000Scm respectively. The nature of redox pseudocapacitance The phase boundary between a metal oxide electrode and an electrolyte solution does not behave like an electrostatic plate capacitor C e.0e.rA d where A denotes the real electrode surface area and d the thickness of the double layer. In practice the so-called pseudocapacitance C f U T . is measured which depends strongly on frequency f temperature T and the applied voltage U because it is not merely an electrostatic quantity but arises from kinetically inhibited redox processes at the metal oxide-electrolyte interface. The electrostatic double-layer capacitance of the Helmholtz layer is always .
