Facile synthesis of diverse transition metal oxide nanoparticles and electrochemical properties

We herein report a facile method for synthesizing a series of metal oxides from the mixture of oleylamine and metal nitrates with heating at 180 °C. Several diverse nanoparticles with various morphologies are gained expectedly: 16.5 nm Mn3O4 nano-capsules, 22 nm CoO nano-cubes, 35 nm NiO nano-flowers and 4 nm Fe3O4 quantum dots. This method is convenient for preparing the dispersed nanoparticles at mild reaction temperature with low-cost metal sources. As-prepared CoO nano-cubes are employed as the electrode material of a pseudocapacitor in terms of implementation. The specific capacitance reaches a stable level of 750 F g−1. This material also exhibits a superior performance in high rate capability and maintains an excellent stability during 9000 recycles. The asymmetric supercapacitor device with a maximum voltage of 1.7 V is fabricated using CoO nano-cubes as the positive and activated carbon as the negative electrode.