Surface-engineered Mo2TiC2Tx MXene for moisture-resilient high-performance energy storage

Abstract

Two-dimensional MXenes are promising electrode materials for electrochemical energy storage; however, their practical deployment is limited by moisture-induced degradation arising from hydrophilic surface terminations. Here, we report a low-energy ion-beam engineering strategy that converts intrinsically hydrophilic Mo₂TiC₂T_x MXene into a moisture-repellent and structurally stable material while preserving its layered architecture. Selective modification of surface terminations yields a robust water contact angle of about 130°, effectively suppressing moisture adsorption and mitigating environmental degradation without inducing structural damage. The ion-beam-treated MXene exhibits nearly a twofold increase in specific capacitance (187 F g⁻¹ at 1 A g⁻¹) and superior long-term cycling stability, with the electrode retaining 80% of its initial capacitance after 10 000 charge–discharge cycles at 5 A g⁻¹, compared with only 55% for the pristine MXene, thereby demonstrating the durability advantage rendered by surface engineering. Post-cycling characterization confirms the retention of the MXene phase identity and structural integrity after long-term charge–discharge cycling, validating the robust electrochemical stability of the irradiated electrode. The improved electrochemical performance originates from irradiation-induced defect formation and electronic structure modulation, which enhance charge transport and pseudocapacitive behaviour. Density functional theory calculations support these findings by revealing reduced adsorption of polar species and an increased density of states near the Fermi level, indicative of enhanced electrical conductivity and quantum capacitance. This work establishes ion-beam surface engineering as an effective route to stabilize Mo₂TiC₂T_x MXene against moisture-driven degradation while concurrently improving their electrochemical robustness.