Electrochemically Modulated Interaction of MXenes with Microwaves

Controlling the reflection and absorption of incident electromagnetic waves at gigahertz frequencies in thin films remains a fundamental challenge. The ability to dynamically depress electromagnetic wave jamming is significant for protecting electronic devices but lacking in conventional electromagnetic interference (EMI) shielding materials. MXenes, as a large family of two-dimensional transition metal carbides and nitrides, have shown a broad range of EMI shielding performance as well as different energy storage mechanisms from electric-double-layer capacitance to pseudocapacitive behavior. Herein, we report a method for active control of electromagnetic wave interactions with various MXene films, including Ti₃C₂T<i>_x</i>, Ti₂CT<i>_x</i>, V₂CT<i>_x</i>, V₄C₃T<i>_x</i> and Nb₄C₃T<i>_x</i>, leading to EMI shields with unprecedented bidirectional modulation of shielding capability. The reversible tunability of EMI shielding effectiveness was achieved by electrochemically driven ion insertion/desertion and charge transfer in MXene layers with different electrolytes, accompanied by expansion and shrinkage of layer spacing. An EMI shielding ‘switch’ was demonstrated through electrochemical oxidation of MXene films. Our results offer opportunities to develop smart EMI protection with active modulation, which is different from conventional ‘static’ shielding and can adapt to demanding environments.