Flexible Asymmetric Photo‐Microsupercapacitor Based on Pseudobrookite‐Type Iron Titanate and V ₂ CT _X MXene for Solar‐Assisted Energy Storage

ABSTRACT

The integration of solar energy harvesting with electrochemical storage represents a promising strategy for next‐generation microsystems. Here, we report a flexible asymmetric photo‐microsupercapacitor (photo‐MSC) based on pseudobrookite‐type iron titanate (FeTi ₂ O ₅ ) and V ₂ CT _x MXene electrodes fabricated on PET substrates. Iron titanate was synthesized from ilmenite via a sustainable route with a potential acid recovery system, yielding defect‐rich nanopowder with a direct band gap of ∼2.31 eV and sub‐bandgap states that enhance visible‐light absorption. The asymmetric configuration leverages complementary charge storage mechanisms using diffusion‐controlled pseudocapacitance in iron titanate and fast surface‐capacitive behavior in MXene, delivering an areal capacitance of 78.99–361.67 mF cm ⁻² . Under simulated solar illumination, capacitance increases by 45.8% at 50 mV s ⁻¹ , with an energy density rising from 64.36 to 93.93 µWh cm ⁻² and power density from 5.80 to 8.45 mW cm ⁻² . This photo‐enhancement originates from efficient photogenerated carrier separation at the iron titanate/MXene heterojunction, confirmed by reduced charge‐transfer resistance and improved carrier dynamics under illumination. The device further demonstrates excellent mechanical flexibility (∼92% capacitance retention at 180° bending) and practical energy delivery capability. This work establishes pseudobrookite iron titanate as a sustainable photoactive electrode material for integrated solar energy storage microsystems.