Pristine Titanium Carbide MXene Films with Environmentally Stable Conductivity and Superior Mechanical Strength

2D titanium carbide (Ti3C2Tx MXene) has potential application in flexible/transparent conductors because of its metallic conductivity and solution processability. However, solution-processed Ti3C2Tx films suffer from poor hydration stability and mechanical performance that stem from the presence of intercalants, which are unavoidably introduced during the preparation of Ti3C2Tx suspension. A proton acid colloidal processing approach is developed to remove the extrinsic intercalants in Ti3C2Tx film materials, producing pristine Ti3C2Tx films with significantly enhanced conductivity, mechanical strength, and environmental stability. Typically, pristine Ti3C2Tx films show more than twofold higher conductivity (10 400 S cm(-1) vs 4620 S cm(-1)) and up to 11- and 32-times higher strength and strain energy at failure (112 MPa, 1,480 kJ m(-3), vs 10 MPa, 45 kJ m(-3)) than films prepared without proton acid processing. Simultaneously, the conductivity and mechanical integrity of pristine films are also largely retained during the long-term storage in H2O/O-2 environment. The improvement in mechanical performance and conductivity is originated from the intrinsic strong interaction between Ti3C2Tx layers, and the absence of extrinsic intercalants makes pristine Ti3C2Tx films stable in humidity by blocking the intercalation of H2O/O-2. This method makes the material more competitive for real-world applications such as electromagnetic interference shielding.