Time-Resolved Electrochemical Kinetics and Pseudocapacitive Charge Storage in Fe-MOF@CoSn-Based Asymmetric Hybrid Supercapacitors

Metal-organic frameworks (MOFs) have attracted significant interest as electrode materials for energy storage systems owing to their tunable structures, large surface areas, and adjustable physicochemical properties. In this study, MIL-100(Fe) was successfully grown on CoSn(OH)₆ (MOF@CTH), and its electrochemical performance was systematically evaluated for asymmetric hybrid supercapacitors (AHS). The charge storage mechanism was elucidated through Dunn analysis, revealing a significant increase in the distinct capacitive contributions for MOF@CTH2. Additionally, the distribution of relaxation times analysis provided detailed insight into electrochemical kinetics, highlighting a capacitive Faradaic and noncapacitive Faradaic charge transfer process occurring within the relaxation timescale of 0.1-1 s for MOF@CTH2. The MOF@CTH2 electrode attained an outstanding specific capacitance of 1124.6 F/g, corresponding to a specific charge of 562.3 C/g. The hybrid two-electrode system constructed with MOF@CTH2 and reduced graphene oxide as the positive and negative electrode, respectively, delivered an energy density of 36.21 Wh/kg and a power density of 749.98 W/kg. This work advances our understanding of time-resolved electrochemical processes in MOF-based systems and highlights their potential in high-performance AHS applications.