Unraveling the Charge Storage Mechanism of Ti₃C₂T_x MXene Electrode in Acidic Electrolyte

Abstract

Two-dimensional Ti3C2T x MXenes have been extensively studied as pseudocapacitive electrode materials. This Letter aims at providing further insights into the charge storage mechanism of the Ti3C2T x MXene electrode in the acidic electrolyte by combining experimental and simulation approaches. Our results show that the presence of H2O molecules between the MXene layers plays a critical role in the pseudocapacitive behavior, providing a pathway for proton transport to activate the redox reaction of the Ti atoms. Also, thermal annealing of the samples at different temperatures suggests that the presence of the confined H2O molecules is mainly controlled by the surface termination groups. These findings pave the way for alternative strategies to enhance the high-rate performance of MXenes electrodes by optimizing their surface termination groups.

Full‐Temperature All‐Solid‐State Ti3C2Tx/Aramid Fiber Supercapacitor with Optimal Balance of Capacitive Performance and Flexibility

“…Therefore, the T/A‐5 fiber electrode is selected for further investigation due to its optimal balance of high tensile strength and superior specific capacitance. Compared with the EDLC behavior of the assembled fibers when the added amount of ANF is 5 wt %, the T/A‐5 fiber electrode shows a pair of redox peaks corresponding to partial pseudocapacitance behavior, [ 27,28 ] especially in low scan rates. It is ascribed to the internal structure of the T/A‐5 fiber electrode, which is more favorable to the electrolyte ion transport (Figure 3f).…”

Two-dimensional MXenes for electrochemical capacitor applications: Progress, challenges and perspectives

“…The H 2 O molecules confined between Ti 3 C 2 T x MXene layers greatly contribute to the fast H + trans port via Grotthuss mechanism by forming a hydrogen bond network [ 177 , 249 ]. As they are essential to trigger the redox activity of Ti and enable the fast charge compensation through high H + diffusion rate, the intercalated H 2 O molecules play a critical role in the pseudocapacitive charge storage mechanism of Ti 3 C 2 T x MXene [249] . On the other hand, the great effect of surface chemistry on the capacitive response in H 2 SO 4 was also verified.…”

“…On the other hand, the great effect of surface chemistry on the capacitive response in H 2 SO 4 was also verified. The presence of − OH terminations on MXene surface can facilitate the intercalation of H 2 O molecules, but a large amount of − OH is assumed to limit the proton transport and thus decrease the power performance [249] . The detrimental effect of F terminations is confirmed by the significantly increased capacitance after replacing the F terminations with the oxygen containing terminations on MXene sur face [181] .…”

Flexible Ti3C2Tx/Graphene Films with Large‐Sized Flakes for Supercapacitors

“…It is accompanied by the change of reversible interpolation/unplugging of protons along with the change of Ti oxidation state. [33][34][35] This charge storage mechanism is based on the Equation (1). [36] Ti…”