Enhanced electrochemical performance of NiO surfaces via selective Li⁺ doping

The effects of selective Li⁺ doping on NiO films' structural, optical and electrochemical properties were investigated in this study. Our results highlighted a strong correlation among bandgap modulation, conductivity and selective Li-ion doping on the surfaces of NiO films. Electrochemical impedance spectroscopy (EIS) demonstrated the impact of subtle Li⁺ doping on the electrochemical behavior of the NiO thin films due to an increase in the diffusion resistance (R_d) up to 49.32 Ω for 0.5% Li-doped NiO, suggesting faster and more efficient hole transport from the electrode to electrolyte unlike NiO:Li4.0% electrodes. A linear and symmetric forward curve demonstrating ohmic behaviour was observed only for 0.5% Li-doped NiO thin films during current-voltage (I-V) analysis. Interestingly, the 0.5% Li-doped NiO films, which exhibited the largest anodic peak area in the CV curve under illumination, outperformed the 4.0% Li-doped NiO films in electrochemical activity, emphasizing the effectiveness of minimal doping.