Ultrathin and flexible MXene-contained electromagnetic interference shielding composite paper designed with a protective hydrogel film

MXene-contained paper is a good choice to design ultrathin and flexible electromagnetic interference (EMI) shielding materials. However, the deficiencies in strength and stability of MXene-contained paper impede its practical applications. Herein, a composite paper was proposed to address the problems, in which a filter paper was modified with a three-layer structured surface via a facile layer-by-layer coating procedure. Specifically, the TEMPO-oxidized cellulose nanofibers (TOCN)/cationic starch (CS)/MXene gel layer and TOCN/MXene nacre structure layer ensured the good EMI shielding and mechanical performances of the composite paper, while the uppermost TOCN/CS hydrogel film layer mainly protected MXene. The composite paper achieved an EMI SE of 40.3 dB at a thickness of merely 0.1894 mm (SE/t value of ca. 212.8 dB mm−1, SSE/t values of ca.13216 dB cm2 g−1) and the total MXene dosage was 20 g m−2. Its tensile strength could be up to 11.7 MPa while the original filter paper was 6.4 MPa. Four pieces of this composite papers could be easily packed together to attain an EMI SE of nearly 70 dB. Importantly, the hydrogel film layer efficiently protected the MXene and maintained the EMI shielding performance of the composite paper when immersed in different liquids including water, HCl (1 M) and ethanol, due to the dense and compact structure of hydrogel film layer. This work provides a practical way to develop ultrathin, flexible and durable EMI shielding materials.