Ni(OH)₂ Nanoparticles Anchored on Laser- and Alkali-Modified TiO₂ Nanotubes Arrays for High-Performance Supercapacitor Application

A simple and effective approach of dual modification of TiO₂ nanotubes (T-NTs) to boost the electronic and electrochemical properties of T-NTs is demonstrated. The T-NTs were doubly modified using alkali treatment and laser irradiation (Na/Las/T-NTs), which led to a fourfold enhancement in capacitance compared to plain T-NTs. Impedance and Mott Schottky analysis showed that the enhanced capacitive performance of the doubly modified T-NTs electrode was due to a decrease in charge transfer resistance by nearly 3 times, a higher charge carrier density value by 1 order of magnitude caused by improved conductivity (alkali treatment), and increased surface area and hydrophilicity (laser irradiation). The Na/Las/T-NTs were then electrodeposited with Ni(OH)₂ nanoparticles (Ni-NPs) to further improve the supercapacitive performances. Ni-NPs electrodeposited on the Na/Las/T-NTs substrate exhibited a high specific capacitance value of 108 mF/cm² (268 mF/g) at a current density of 0.08 mA/cm². In addition, the substrate had an energy density of 4.7 µWh/cm² at a power density of 2 mW/cm² . showing an efficient charge storage capacity compared to most previously reported TiO₂ s-based supercapacitors. Furthermore, the proposed supercapacitor possessed an excellent cyclic and electrochemical stability after 6000 cycles with nearly 88% capacitive retention and 90% coulombic efficiency. Overall, the doubly modified T-NTs surface favors improved electronic contact of Ni-NPs that promotes a more feasible electro-redox reaction at the electrode–electrolyte interface, and thereby demonstrates an effective approach to enhance the performance of supercapacitors.