Facile synthesis of mesoporous ZnCo2O4 hierarchical microspheres and their excellent supercapacitor performance

ZnCo2O4 hierarchical microspheres assembled by a large amount of porous nanosheets with 15 nm in thickness were synthesized via a simple solvothermal approach in a mixed solvent containing water and ethylene glycol (EG), and combined with a subsequent calcination process at 400 degrees C in air. These nanosheet-based ZnCo2O4 microspheres possessed a high BET surface area of 67.1 m(2) g(-1) and pore size distribution centered at 4.6 nm with a mean pore diameter of 28.6 nm. The pseudocapacitive performances of such ZnCo2O4 electrode material were investigated by the related electrochemical tests in 2 M of KOH electrolyte, and the results indicated that a highly specific capacitance of 689 F g(-1) at 1 A g(-1) and a good rate capability of 81.3% capacitance retention at 15 A g(-1) could be achieved. After a consecutive 5000 charge-discharge cycling process at 5 A g(-1), the ZnCo2O4 modified electrode exhibited 98.7% specific capacitance retention of its original value, suggesting a superior long-life cycling durability. The excellent electrochemical performances of the ZnCo2O4 hierarchical microspheres make it a promising and suitable electro-active material for energy storage. The current synthetic process is facile without using any sophisticated instruments or expensive reagents. The strategy can be further adopted for the synthesis of other binary transitional metal oxides with superior electrochemical properties by simple replacement of starting salts.