Nanoporous NiCo2O4 Nanorod Arrays Enable Photo-Assisted Aqueous Alkaline Zn Battery with Enhanced Capacities

NiCo2O4 has been widely applied in energy storage devices due to high theoretical capacity and excellent electronic conductivity. However, limited kinetics in redox reactions makes the specific capacity of NiCo2O4 much smaller than its theoretical value. In this paper, the electrochemical properties of NiCo2O4 are effectively improved with a light illumination method. The specific capacity (140.8 mA h g-1) of NiCo2O4 electrode under light is larger about-27 % than that in dark, indicating that NiCo2O4 electrode has remarkable photoirradiation enhanced capacity behavior. The reason for this behavior is that generated holes on the photoelectrode under light illumination can promote electrochemical reaction with OH-. In addition, an alkaline Zn battery with NiCo2O4 nanorod arrays as photocathode also shows good PIEC behavior. Under light illumination, this battery exhibits high specific capacity of 130.6 mA h g-1, large energy density of 220.7 Wh kg-1 and good cyclic stability. This work provides a new perspective for improving energy storage performance of semiconductor materials based electrochemical batteries.