Porous nickel oxide nano-sheets for high performance pseudocapacitance materials

We report a new nano-geometry based on porous nickel oxide nano-sheets for high performance pseudo-capacitance materials. The porous nickel oxide nanosheets were fabricated by synthesizing porous Ni(OH)(2) sheets by surfactant-templated wet chemistry followed by the decomposition of hydroxides to oxides upon thermal treatment. The nickel oxide nanosheets display tunable specific capacitance varying from 641 to 1025 F/g at a charge-discharge current density of 3 A g(-1), and from 326 to 445 F/g at 15 A/g. By optimizing the thermal annealing conditions (e.g., 300 degrees C for 3 h), the electrochemical performance can be achieved with a high capacitance of 993 F/g at current density of 3 A g(-1), and 445 F/g at 15 A g(-1) with an excellent cycle stability. Detailed XRD, CV, EIS, UV and XPS characterization indicated that the interplay among the surface area, morphology, pore size distribution, crystal size and defect determined the electrochemical performance of porous NiO nanosheets as pseudocapacitive materials. The unique nano-sheet geometry and intrinsically high surface area may have a great potential for designing high performance supercapacitors with simultaneous high power and energy densities, and the reported surfactant-templated wet chemistry approach may also be applicable for developing various metal oxide nano-sheet pseudo-capacitance materials for electrochemical energy storage.