Supercapacitors are an alternative to batteries. They charge and discharge very fast, but usually have much smaller capacities. Co3O4 nanosheets are a material with a high theoretical specific capacitance, which could improve the energy storage capacity of supercapacitors.
Xuefeng Guo, Nanjing University and Huanggang Normal University, both China, and colleagues have synthesized a range of two-dimensional Co3O4 nanosheets with different amounts of oxygen vacancies for use in supercapacitors. The team first prepared cobalt hydroxide precursors, which were calcined at 300 °C in air to give Co3O4 nanosheets. The nanosheets were then reduced to create oxygen vacancies, either in a mixture of hydrogen and nitrogen or in an NaBH4 solution. The resulting nanosheets have a thickness of about 20 nm and retain the overall structure of pristine Co3O4 nanosheets.
The researchers found an increasing number of oxygen vacancies from the pristine nanosheets, to the hydrogen-reduced ones, to the NaBH4-reduced material. The electrical conductivities and specific capacitances of the respective nanosheets increase in the same order. The oxygen-vacancy-rich NaBH4-reduced Co3O4 nanosheets have an excellent electrochemical performance, making them a promising material for supercapacitors.
- Two dimensional oxygen-vacancy-rich Co3O4 nanosheets with excellent supercapacitor performances,
Kun Xiang, Zhicheng Xu, Tingting Qu, Zhengfang Tian, Yu Zhang, Yongzheng Wang, Mingjiang Xie, Xiangke Guo, Weiping Ding, Xuefeng Guo,
Chem. Commun. 2017.