Flexible TiN/Co@Carbon nanofiber mats for high-performance electromagnetic interference shielding and Joule heating applications

Carbon nanofibers (CNFs) are self-standing, lightweight and stable materials that naturally suitable for electromagnetic interference (EMI) shielding and Joule heating applications. However, intrinsic low conductivity severely restricts the operational performance of CNFs. Current methods that can improve the conductivity of CNFs inevitably sacrifice their flexibility for exchange. This work develops a nitride forming metal and magnetic metal codope method of nitrogen-doped CNFs by using electrospinning and annealing, and obtains highly conductive and flexible CNFs embedded with TiN and Co nanoparticles (TCCNFs). Multiple characterizations and electrical and mechanical tests are carried out to reveal that the strong Ti–N covalent bond can enhance the mechanical robustness and the Co nanoparticles contribute to improve the conductivity of CNFs. As a result, a multilayer porous TCCNF mat exhibits an ultrahigh EMI shielding effectiveness of 93 dB in the 8.2–12.4 GHz frequency range due to the combined effects of multi-reflection, dielectric polarization relaxation, and conducting and magnetic loss processes. Additionally, the TCCNF mat-based heater shows the highest Joule heating efficiency of 1508 °C W−1 cm2 among the flexible conductive materials and a superfast Joule heating (cooling) rate of 28 (31) °C/s. The TCCNF mat-based heater is able to reduce the restoring time of Ti3C2Tx MXene humidity sensor by about 78%. The TCCNF mats should also be potential electrode materials for wearable electronics.