Improved capacitance of NiO and nanoporous silicon electrodes for micro-supercapacitor application

Abstract

We investigated the NiO/PS/Si and the NiO/Si electrodes to highlight the effect of the PS porous silicon on the enhancement of the electrode performance. We elaborated the PS with the stain etching method, whereas the NiO nickel oxide was synthesized using sol–gel and deposited through the spin coating technique. We showed that PS porous silicon significantly increased the active surface area and improved the electrical and electrochemical properties. Thus, we obtained promising results for NiO/PS/Si. The effective series resistance and interfacial resistances were reduced from 1.8 Ω cm² and 42 Ω cm² to 0.05 Ω cm² and 0.29 Ω cm² from NiO/Si to NiO/PS/Si, respectively. The capacitance increased from 12.34 µF cm⁻² for NiO/Si to 9.64 mF cm⁻² for NiO/PS/Si. We found similar capacity values from the CV cyclic voltammetry curves and IS impedance spectroscopy Nyquist plots. We obtained equivalent effective series resistance values from the charge–discharge and Nyquist plots, confirming our results. The NiO/PS/Si electrode showed good stability with only a 3% loss for 5000 galvanostatic cycles. The energy efficiency is estimated from the charge–discharge curves to be 91%.