Plasma‐Activated Solutions Regulate Surface‐Terminating Groups Enhancing Pseudocapacitive Ti3C2Tx Electrode Performance

Abstract

Abstract2D transition metal carbides and nitrides (MXenes) are actively pursued as pseudocapacitive materials for supercapacitors owing to their advantages in electronic conductivity and surface reactivity. Increasing the fraction of ─O terminal groups in Ti3C2Tx is a promising approach to improve the pseudocapacitive charge storage in H2SO4 electrolytes, but it suffers from a lack of effective functionalization methods and stability of the groups in practical operation. Here a low‐temperature and environment‐friendly approach via the interaction of nonequilibrium plasmas with Ti3C2Tx dispersion is demonstrated to generate abundant and stable surface‐terminating O groups. The impact of the discharge environment (Ar, O2, and H2) on the structural characteristics and electrochemical performance of Ti3C2Tx nanosheets is studied. The Ti3C2Tx modified in Ar and H2 maintains their original morphology but a significantly lower F content. Consequently, an extraordinarily high content (78.5%) of surface‐terminating O groups is revealed by the high‐resolution X‐ray photoelectron spectroscopy spectra for the Ti3C2Tx samples modified in H2 plasma‐treated solutions. Additionally, the Ti3C2Tx treated using H2 plasmas exhibits the best capacitive performance of 418.3 F g−1 at 2 mV s−1, which can maintain 95.88% capacity after 10 000 cycles. These results contribute to the development of advanced nanostructured pseudocapacitive electrode materials for renewable energy storage applications.