Electronegativity-driven ion kinetics in Ti₃CNTₓ MXene for high-performance electro-ionic soft actuation

Abstract

MXene-based electrodes have emerged as promising materials for electro-ionic soft actuators, yet their performance remains largely limited to the extensively studied Ti3C2Tx composition. Here, we introduce Ti3CNTx MXene as a chemically engineered alternative and reveal how nitrogen incorporation fundamentally enhances ion kinetics and actuation behavior. When integrated with PEDOT:PSS (PP), the Ti3CNTx-PP composite electrode demonstrated markedly superior electrochemical performance, achieving an areal capacitance of 562 mF cm⁻²—significantly higher than Ti3C2Tx-PP (204 mF cm⁻²) and pristine PP (159 mF cm⁻²). This enhancement originates from the higher electronegativity of Ti–N bonding, which increases redox-active sites, enlarges interlayer spacing, and accelerates ion diffusion within the MXene framework. Under a low driving voltage of 1 V at 0.1 Hz, the Ti3CNTx-PP actuator exhibited a peak-to-peak displacement of 14.5 mm, outperforming Ti3C2Tx-PP (8.05 mm) and pristine PP (5.5 mm). Frequency- and voltage-dependent actuation tests further confirmed the dominance of Ti3CNTx across all conditions, highlighting its fast ion transport and stronger charge-induced deformation. These findings establish nitrogen-rich Ti3CNTx as a high-efficiency MXene for low-voltage soft actuation and demonstrate electronegativity-driven composition engineering as a powerful strategy for advancing soft robotics, artificial muscles, and next-generation electro-active devices.