Abstract: Iron oxide film directly grown on iron, steel, or other substrates by chemical or electrochemical oxidation is a promising material for energy storage through surface adsorption of static charges. As the electrode materials of energy-storage devices, the hydrated iron compound has a chemical composition of FexOyHz, where 1.0≦x≦3.0, 0.0≦y≦4.0, and 0.0≦z≦1.0. An aqueous or organic solution of a metallic salt including sulfates, sulfites, hydroxides, chlorides, phosphates and nitrates is used as electrolyte for the electrochemical devices. Cyclic voltammetry indicates that the iron-oxide electrodes in the electrolytes can store charges as high as 0.5 F/cm2 or 320 F/g of the electrode materials. Electrochemical capacitors using the iron oxide as the electrode material is an economical and viable power source for use in portable electronics, power tools, and electrical vehicles.

Abstract: Iron oxide film directly grown on iron, steel, or other substrates by chemical or electrochemical oxidation is a promising material for energy storage through surface adsorption of static charges. As the electrode materials of energy-storage devices, the iron oxide has a chemical composition of FexOyHz, where 1.0≦x≦3.0, 0.0≦y≦4.0, and 0 0≦z≦1.0. An aqueous or organic solution of a metallic salt including sulfates, sulfites, hydroxides, chlorides, phosphates and nitrates is used as electrolyte for the electrochemical devices. Cyclic voltammetry indicates that the iron-oxide electrodes in the electrolytes can store charges as high as 0.5 F/cm2 or 320 F/g of the electrode materials. Electrochemical capacitors using the iron oxide as the electrode material is an economical and viable power source for use in portable electronics, power tools, and electrical vehicles.