NiCo2O4 with oxygen vacancies as better performance electrode material for supercapacitor

In this paper, using a chemical reduction method, oxygen vacancies are introduced into different NiCo2O4 nanostructures, crystal structure analyses and electrochemical property studies on oxygen vacancies are further described by two sets of in situ control experiments. Electrochemical data show that reduced NiCo2O4 electrodes with appropriate oxygen vacancies exhibit a significant improvement on electrical conductivity and capacitance compared to the untreated electrodes. Interestingly, the capacitance of the reduced NiCo2O4 nanosheets electrode (0.5-NiCo2O4 NS-vac) and the reduced NiCo2O4 nanowires electrode (0.5-NiCo2O4 NW-vac) obtained from 0.5 M NaBH4 solution is significantly higher than that of the pristine electrodes, and has increased by 77% and 100.4%, respectively. Due to the introducing of oxygen vacancies in NiCo2O4, part of Co-O and Ni-O bonds in the crystals are destroyed and the crystalline degree of the crystals decreases. However, the reduced NiCo2O4 electrodes still maintain excellent cycling performance after cyclic test. These results indicate that the appropriate oxygen vacancies in NiCo2O4 can be an efficient strategy for enhancing the performance of NiCo2O4.