https://doi.org/10.1002/est2.70246
In this study, we report the effect of bromine treatment on electrochemically synthesized TiO2 nanotube (TNT) electrodes for supercapacitor applications. The bromine-treated TNT electrodes, exhibiting an anatase crystal structure, showed a sixfold enhancement in specific capacitance compared to untreated TNTs, achieving a high gravimetric specific capacitance of 330 F g−1 and an areal specific capacitance of 135.59 mF cm−2 at a current density of 2.5 mA cm−2. Furthermore, the electrodes demonstrated exceptional cycling stability, retaining 100% of their capacitance after 5200 charge–discharge cycles. This remarkable performance enhancement is attributed to the generation of oxygen vacancies within the anatase lattice upon bromine treatment, along with a significant reduction in charge transfer resistance at the electrode–electrolyte interface. The material properties of the electrodes were comprehensively characterized using x-ray photoelectron spectroscopy, transmission electron microscopy, field-emission scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. In addition, a prototype symmetric supercapacitor fabricated using the bromine-treated electrodes delivered a specific capacitance of 36.3 F g−1 at a scan rate of 5 mV s−1, a power density of 3.69 kW kg−1 and a capacitance retention of 100% over 2000 cycles.