Post-synthesis laser treatment, characterization, and enhanced electrochemical properties of Fe–TiO2 for supercapacitors

This study presents a novel approach to enhancing the electrochemical performance of TiO₂-based supercapacitors through controlled iron (Fe) doping and post-synthesis laser treatment. Fe-doped TiO₂ nanocrystals (FTNCs) were synthesized via a sol–gel method, with doping concentrations optimized at Fe-3 and 5 wt%. Structural and morphological analyses revealed that Fe³⁺ ions substituted into the TiO₂ lattice, inducing crystallite size enlargement (from 25.75 nm for pure TiO₂ to 39.92 nm for Fe-5 wt% TiO₂) alongside reduced microstrain and dislocation density, contrasting conventional doping-induced size reduction trends. Post-synthesis laser treatment further refined crystallinity and electronic properties, promoting homogeneous dopant distribution and reduced charge recombination. Electrochemical evaluations demonstrated superior performance for Fe-5 wt% TiO₂, achieving a specific capacitance of 93.23 Fg⁻¹ at 5 mVs⁻¹, significantly surpassing undoped TiO₂ 17 Fg⁻¹, and outperforming many reported TiO₂-based systems. The enhanced performance is attributed to Fe-induced oxygen vacancies, pseudocapacitive redox activity, and improved charge transfer kinetics, evidenced by a low charge transfer resistance (1.12 Ω) in EIS analysis. This work underscores the efficacy of controlled Fe doping in optimizing TiO₂ for energy storage, offering new insights into defect engineering and post-processing strategies. The findings highlight the potential of Fe–TiO₂ nanocrystals as high-performance electrode materials for next-generation supercapacitors, with prospects in multi-element co-doping and hybrid composite architectures.