MXenes for electromagnetic interference shielding: Insights from structural design

The rapid development of modern electronic devices and communication technology has led to a significant increase in the pollution of electromagnetic wave radiation. Metals, such as copper, aluminum and nickel, were generally applied to reduce electromagnetic interference (EMI). However, with the increasing miniaturization of electronic devices, there is a growing demand for the flexibility and light-weight of shielding materials. Recently, MXene has received considerable attentions in EMI shielding due to its good conductivity, large specific surface area, light weight and excellent flexibility. Although good conductivity is beneficial to EMI shielding, the reflection of electromagnetic waves will bring about the secondary pollution. Thus the efficient absorption of electromagnetic waves inside the shielding materials is quite important to endow a green shielding, which can be realized through the design of MXene structures to enhance internal scattering. In this review, we reported the very recent progress of MXenes as EMI shielding materials from its structural design. Firstly, the fundamental theory of EMI shielding was discussed in depth with the focus on the impact factors and the evaluation systems. In the next, MXenes for EMI shielding are summarized with different structures including layer-by-layer and porous MXenes (foams, aerogels and hydrogels), in which the function and the design of internal scattering are carefully discussed from MXene structures. Finally, a conclusion and perspective is given to indicate current challenges and future directions in MXene-based EMI shielding.