Cellulose nanofiber/MXene/mesoporous carbon hollow spheres composite films with porous structure for deceased reflected electromagnetic interference shielding

Conductive polymer composites (CPCs) have always attracted great attention in the development of electromagnetic shielding materials. However, how to solve the conflict between high electromagnetic (EM) waves reflection and high electromagnetic interference (EMI) shielding performance brought by conductive fillers is becoming an urgent problem. In this study, a homogeneous composite film with porous structure was constructed by vacuum filtration using cellulose nanofibers (CNF), MXene, and mesoporous carbon hollow spheres (MCHS). Benefiting from the porous structure, the impedance match between the composite film and the air was improved, thereby reducing the reflection of electromagnetic waves. In addition, the hollow porous structure of MCHS was beneficial to the multiple reflections and interfacial losses of EM waves in its pores and between the interfaces of MXene and MCHS, thereby further reducing the EM waves reflection. The obtained CNF/MXene/MCHS composite film with 10 wt% MCHS exhibits electromagnetic interference shielding effectiveness (EMI SE) of 24.6 dB, the reflection value (R) become 0.72, and the reflection effectiveness drops to 5.5 dB, which greatly improved the absorption of electromagnetic waves while meeting the commercial application standards. Hence, the preparation strategy of this work provides a concise, efficient, and controllable method for the subsequent development of low-reflection porous structured composite films.