Exfoliation and Defect Control of Two-Dimensional Few-Layer MXene Ti₃C₂T<i>_x</i> for Electromagnetic Interference Shielding Coatings

Abstract

Defect-controlled exfoliation of few-layer transition-metal carbide (<i>f</i>-Ti₃C₂T<i>_x</i>) MXene was demonstrated by optimizing chemical etching conditions, and electromagnetic interference (EMI) shielding coatings were explored. The structural features such as layer morphology, lateral size, layer thickness, defect density, and mechanical stability of the exfoliated <i>f</i>-Ti₃C₂T<i>_x</i> were strongly dependent on exfoliation conditions. By selecting appropriate exfoliation conditions, moderate etching time leads to the formation of quality <i>f</i>-Ti₃C₂T<i>_x</i> with lesser defects, whereas longer etching time can break the layer structure and increase defect density, structural misalignment, and oxidative products of <i>f</i>-Ti₃C₂T<i>_x</i>. The resultant fabricated free-standing flexible <i>f</i>-Ti₃C₂T<i>_x</i> films exhibited electrical conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) in the X-band of about 3669 ± 33 S/m and 31.97 dB, respectively, at a thickness of 6 μm. The large discrepancy in EMI SE performance between quality (31.97 dB) and defected (3.164 dB) <i>f</i>-Ti₃C₂T<i>_x</i> sheets is attributed to interconnections between <i>f</i>-Ti₃C₂T<i>_x</i> nanolaminates interrupted by defects and oxidative products, influencing EMI attenuation ability. Furthermore, the demonstrated solution-processable high-quality <i>f</i>-Ti₃C₂T<i>_x</i> inks are compatible and, when applied for EM barrier coating on various substrates, including paper, cellulose fabric, and PTFE membranes, exhibited significant EMI shielding performance. Moreover, controlling defects in <i>f</i>-Ti₃C₂T<i>_x</i> and assembly of heterogeneous disordered carbon-loaded TiO₂-Ti₃C₂T<i>_x</i> ternary hybrid nanostructures from <i>f</i>-Ti₃C₂T<i>_x</i> by tuning etching conditions could play an enormous role in energy and environmental applications.