Electrochemical Impedance Analysis of Ti3C2Tx MXene for Pseudocapacitive Charge Storage

This study investigates the electrochemical behavior of Ti3C2Tx MXene for supercapacitor applications, focusing on its charge storage mechanisms using Electrochemical Impedance Spectroscopy (EIS). A novel equivalent circuit (EC) model, incorporating a diffusion layer resistance and a constant phase element, was developed to represent the impedance spectra, achieving a low error margin of 4.6%. The cycling stability of MXenes and charge storage parameters were evaluated using the developed EC model. This study demonstrated that the irreversible anodic oxidation of MXene begins around 0.3 V due to water molecule attack from the aqueous electrolyte, resulting in the formation of a titanium oxide layer that increases charge transfer resistance and impairs charge storage. It was further revealed that the cycling stability of MXene is also related to the oxidation of MXene, and the initial capacitance of 493 F/g at 100 mV/s is reduced by 27.5% after 1000 cycles. The contribution of charge storage factors was analyzed, with 85% of MXene’s capacitance found to be surface controlled. This research offers a deeper understanding of MXene’s charge storage mechanisms, providing critical insights into optimizing its electrochemical performance and stability. By establishing advanced modeling approaches and addressing challenges related to oxidation and resistance, this work enhances MXene’s potential for high-power supercapacitors in electromechanical actuator applications.