Enhancing Heating Efficiency and Protection of MXene Through Graphene Skin

Ti₃C₂T_x MXene has outstanding characteristics of high electrical conductivity and facile processability in benign water solvents, and has been highlighted as a versatile Joule heating material with low-voltage operation with stable heating performance. However, MXene can be easily oxidized in warm and damp environments due to its plentiful hydrophilic functional groups on sheets. In addition, the high convective heat loss from the MXene surface limits their heating efficiency. Therefore, we tailored a multifunctional graphene skin (with a thickness of ~370 nm) for MXene, to protect the venerable surface properties of MXene. Both MXene and graphene layers have tortuous pathways with similar layered structures; however, the water impermeability of graphene was ~70 times higher than that of bare MXene due to narrow d-spacing and the hydrophobic nature of graphene skin. In addition, we found that the heat loss regulation effect of graphene skin increased the heating efficiency, indicating that the graphene skin is promising for developing adaptive heating materials. Our research has inspired a new hybrid skin strategy that exploits the full potential of materials for developing functional coatings for various applications.