High‐Performance Symmetric Supercapacitor Enabled by Mn‐Doped TiO₂‐Nanostructured Electrodes: Unraveling Electrokinetic Contributions and Surface Redox Dynamics

Developing sustainable and scalable electrode materials remains a pressing challenge in advancing high‐performance supercapacitors. Herein, a green, low‐cost hydrothermal synthesis of nanostructured manganese‐doped titanium dioxide (Mn–TiO 2 ) with tunable doping concentrations (3%, 6%, and 12%) for application in symmetric supercapacitor devices is reported. Among the compositions, 12% Mn‐doped TiO 2 (12MTO) demonstrates exceptional electrochemical properties, delivering a high specific capacitance of 720 F g −1 (cyclic voltammetry, 5 mV s −1 ) and 278.3 F g −1 (galvanostatic charge–discharge, 1 A g −1 ), significantly outperforming undoped TiO 2 . The 12MTO‐based symmetric supercapacitor exhibits a wide voltage window of 2 V, an energy density of 24.7 Wh kg −1 , and a power density of 352.5 W kg −1 , while retaining 87% of its capacitance after 5000 cycles. Electrochemical impedance spectroscopy and kinetic analysis reveal improved charge transport, reduced resistance, and a dominant pseudocapacitive behavior (86% contribution), attributed to Mn‐induced oxygen vacancies and surface redox tuning. The process demonstrates excellent reproducibility and eco‐friendly scalability, highlighting Mn‐doped TiO 2 as a sustainable electrode material for next‐generation energy storage technologies with industrial relevance.