Scalable Production of Highly Conductive 2D NbSe 2 Monolayers with Superior Electromagnetic Interference Shielding Performance.

Thin, flexible, and electrically conductive films are in demand for electromagnetic interference (EMI) shielding. Two-dimensional NbSe 2 monolayers have an electrical conductivity comparable to those of metals (10 6 -10 7 S m -1 ) but are challenging for high-quality and scalable production. Here, we show that electrochemical exfoliation of flake NbSe 2 powder produces monolayers on a large scale (tens of grams), at a high yield (>75%, monolayer), and with a large average lateral size (>20 μm). The as-exfoliated NbSe 2 monolayer flakes are easily dispersed in diverse organic solvents and solution-processed into various macroscopic structures (e.g., free-standing films, coatings, patterns, etc.). Thermal annealing of the free-standing NbSe 2 films reduces the interlayer distance of restacked NbSe 2 from 1.18 to 0.65 nm and consequently enhances the electrical conductivity to 1.16 × 10 6 S m -1 , which is superior to those of MXenes and reduced graphene oxide. The optimized NbSe 2 film shows an EMI shielding effectiveness (SE) of 65 dB at a thickness of 5 μm (>110 dB for a 48-μm-thick film), among the highest in materials of similar thicknesses. Moreover, a laminate of two layers of the NbSe 2 film (2 μm thick) with an insulating interlayer shows a high SE of 85 dB, surpassing that of the 20-μm-thick NbSe 2 film (83 dB). A two-layer theoretical model is proposed, and it agrees with the experimental EMI SE of the laminated NbSe 2 films. The ability to produce NbSe 2 monolayers on a tens of grams scale will enable their diverse applications beyond EMI shielding.