Exploring Feedstock Recycling in Liquid-Phase-Exfoliated Nanosheets

Industrial scale-up of two-dimensional (2D) nanomaterial production is essential if these novel materials are to prove themselves commercially viable for applications ranging from energy conversion and storage to optoelectronic devices and clean water. There are several techniques to produce 2D materials, and liquid phase exfoliation (LPE) is one that has emerged as the most widespread across laboratory, pilot, and industrial production scales. One of the main issues faced in the scale-up of such techniques is the low yield (typically 0.5-5 wt %), resulting in high levels of wasted feedstock material. Similarly, every 10 kg of product can create 1000 L or more of solvent waste, many of which are highly toxic to the environment (e.g., NMP). Using MoS as a prototypical 2D material, this work demonstrates a sustainable approach to recover and reuse unexfoliated precursor material and the exfoliation solvent to reduce waste by up to 82% and solvent requirement by up to 72%. Material production efficiency benefits were also achieved, with over 3-fold increase in product yield and energy usage reduced by up to 12%. The approach can be easily scaled and immediately implemented using existing infrastructure, and a pathway for industrial implementation has been outlined to support this.