Facile synthesis of porous ZnO-NiO composite micropolyhedrons and their application for high power supercapacitor electrode materials.

Porous ZnO-NiO composite micropolyhedrons have been successfully synthesized by calcination of mixed oxalate (Zn(0.9)Ni(0.1)(C(2)O(4))(2)·nH(2)O) precursors in air. The oxalate precursor micropolyhedrons were synthesized by a mild chemical precipitation method without any template or surfactant, and found to have a relatively low decomposition temperature. We have successfully explored the application of the resulting porous ZnO-NiO composite micropolyhedrons as electrochemical capacitors. Electrochemical study shows that the obtained ZnO-NiO composites under different conditions have different electrochemical supercapacitor properties in 3.0 or 1.0 M KOH solutions. The porous ZnO-NiO micropolyhedron material (P1) obtained by calcination of the oxalate precursor at 400 °C has a large specific capacitance 649.0 F g(-1) in 3.0 M KOH solution and could maintain 99.1% of this value after 400 cycles at 5.8 A g(-1). Even at a high current density of 58.0 A g(-1), the specific capacitance of P1 is 395.2 F g(-1).