Preparation And Capacitive Study Of In-Situ Synthetized Nano Metal Oxide Material On Porous Metal Surface

Supercapacitors,known as electrochemical capacitors,are considered as promising candidates for energy storage because they have the advantages of higher power densities,longer cycle lives,a short charging time,wide working temperature range and so on.Among the array of electrode materials for supercapacitor applications,transition metal oxides are widely studied due to variable oxidation states of metal ions which facilitate redox transitions and higher charge storage within the potential range of water decomposition.MnO₂ and Co₃O₄ are considered to be promising materials for supercapacitors because of their high theoretical specific capacitances,natural abundance and evironmentally friendliness.However,the practical capacitive behavior of these two oxides is far from their theoretical values due to their poor electrical conductivity and mechanical instability.In this work,we aim to enhance the conductivity of these two electrode materials,composites with nanosized MnO₂ and Co₃O₄ grown on the surface of conductive nanoporous metals were prepared,which can make full use of the excellent conductivity of nanoporous metals.The main contents of this paper:1.Novel M@MnO₂?M=Ni,Cu,and Ag?nanoporous electrode materials were designed and fabricated through a simple dealloying method and a redox reaction process occurring between KMnO₄ and nanoporous metal.Benefiting from their unique structures and excellent electrical conductivity,the Cu@MnO₂ electrode materials of supercapacitors shows high specific capacity of 1088 F g^-1 at the current density of 2 A g^-1 and good capacity retention?74.7%?after 10000 electrochemical cycles even at a high current density of 10 A g^-1.2.A freestanding,highly conductive,hierarchical porous Ni foam networks was fabricated through a dealloying method,and loaded with MnO₂ by electrodeposition,as the electrodes of a supercapacitor.It was found that the three-dimensional?3D?composite electrode showed an ideal supporter for active materials and leading to a high specific capacitance of 1266 F g^-1 at a scan rate of 1 mV s^-1.In order to compare the contribution of the collector to the specific capacitance,MnO₂ was also electrodeposited onto Ni foams with deposition mass ranging from 0.05 to 0.5 mg cm^-2 under the same conditions used for the hierarchical porous foam nickel collector.This hierarchical porous foam nickel might provide a platform for growth other high-performance,low-cost,and environmentally friendly materials used in energy conversion and storage systems for the effective use of renewable energy.3.Nanoporous Ni-Co₃O₄ composite electrode material with high porosity has been synthesized through a facile dealloying process in air at room temperature.The composite consisted of well-arranged micropore and nanopore with high specific surface area,pore volume,and uniform pore size distribution.The charge-discharge study shows that the composite material is capable of delivering very high specific capacitance of 2987 F g^-1 at a current density of 1 A g^-1 and retains 67%of capacitance at 40 A g^-1.