Strategic Defect and Phase Engineering of Titanate Nanotube Arrays for Next‐Generation High‐Performance Supercapacitors

ABSTRACT This work explores the influence of two different fabrication strategies on the electrochemical performance of Fe doped TiO 2 nanotube electrodes for supercapacitors. Electrodes of anatase phase (TNT/Fe‐450) and mixed phases of TiO 2 (B) and brookite (TNT/Fe‐60) were prepared, respectively, by the conventional electrochemical anodization and a novel “water‐bath temperature‐controlled anodization” method, respectively. While the TNT/Fe‐450 electrode exhibited a maximum areal (gravimetric) specific capacitance of only 86.48 mF cm −2 (166.30 F g −1 ), the TNT/Fe‐60 showed nearly 10‐fold enhancement in energy storage efficiency, with a maximum specific capacitance of 952.59 mF cm −2 (1693.49 F g −1 ) from cyclic voltammetry. Galvanostatic charge discharge measurements yielded a maximum specific capacitance (Cs) of 1427.99 F g −1 , an energy density (ED) of 300 W h kg −1 and a power density (PD) of 2.43 kW kg −1 , for TNT/Fe‐60. Asymmetric supercapacitors of two configurations with TNT/Fe‐60 as the negative electrode and either activated conducting carbon cloth (ACC) or MnO 2 over CC, as the positive electrode were assembled. The MnO 2 ‐paired ASC demonstrated the best performance, with a high Cs of 352.19 Fg −1 at 10 mV s −1 , ED of 94.05 W h kg −1 , PD of 5.46 kW kg −1 , and 100% capacity retention in 5 k cycles, indicating its potential for high energy storage applications.