Topochemical Conversion of Ti3AlC2 to Ti3C2T x MXene via Kinetically Accelerated Microwave Etching and Targeted Byproduct Purification

Abstract

Achieving high synthesis throughput without sacrificing the structural integrity of two-dimensional (2D) Ti3C2Tx MXenes remains a primary challenge, as conventional minimally intensive layer delamination (MILD) requires prolonged etching (∼24 h) that induces surface degradation and nonstructural carbon defects. Herein, we demonstrate a rapid microwave-assisted (MW) etching strategy combined with targeted sulfuric acid (H2SO4) byproduct purification to produce highly crystalline Ti3C2Tx MXenes within 1 h of total process time (120 °C MW etching for 30 min; 100 °C H2SO4 washing for 30 min). Avrami-Erofe’ev kinetic modeling reveals that MW irradiation reduces the apparent activation energy (Ea) to 25.51 ± 0.73 kJ mol–1 (R2 = 0.9976)─approximately 54% lower than the conventional HF etching benchmark (55.2 kJ mol–1)─significantly accelerating topochemical conversion. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) confirm that this accelerated kinetic regime effectively suppresses acidic overetching, yielding a lower relative C–C defect ratio (47.25%) while fully preserving the Ti–C framework. Furthermore, postpurification with 3 M H2SO4 completely removes insoluble crystalline Li3AlF6 byproducts. The resulting predominantly single- to few-layer delaminated MXene nanosheets assemble into flexible freestanding films with an outstanding electrical conductivity of 2.64 × 103 S cm–1. This work establishes a scalable kinetic pathway for high-speed, defect-minimized manufacturing of 2D MXenes.