In situ synthesis of NiO@Ni micro/nanostructures as supercapacitor electrodes based on femtosecond laser adjusted electrochemical anodization

Highlights: • Micro/nanostructures were fabricated by femtosecond laser pre-treatment. • The micro/nanostructures affected ion migration during electrochemical anodization. • The performance of electrode was better than that of the absence of fs laser. Nickel oxide is a p–type transition metal oxide with excellent electrochemical performance, which is widely used in the application of supercapacitors. We introduce an approach of femtosecond laser ablation combined with electrochemical anodization for NiO nanostructures grow in situ on nickel sheet for supercapacitors electrodes. By controlling the processing conditions of femtosecond laser, various patterns covered the surface of nickel sheet, which promoted uniform NiO growth in situ on nickel sheet. Specific capacitance of the supercapacitor electrode fabricated using femtosecond laser pretreatment was superior to that of the NiO/Ni electrode prepared by electrochemical anodization alone at the current density of 1 mA cm⁻². In addition, the capacitance retention of the NiO/Ni electrode for 1500 cycles was approximately 100%, and this electrode exhibited excellent conductivity according to electrochemical impedance spectroscopy measurements. According to these results, femtosecond laser enhanced electrochemical anodization was a promising approach for the fabrication of supercapacitors electrodes.