GOALI: Manufacturing of Two-Dimensional MXene Nanosheets by Salt Solution Etching and Their Solution-based Layer-by-Layer Assembly into Heterostructures

MXenes are a broad family of two-dimensional (2D) ceramic nanosheets with a wide compositional diversity and tailorability of properties for a broad range of practical applications, including energy storage, catalysis, electromagnetic interference shielding, sensors, composites, and batteries. However, challenges in the advanced manufacturing of MXenes prevent widespread production and use. Manufacturing challenges include (i) difficulties in synthesizing MAX phases beyond titanium aluminum carbide, (ii) the use of hazardous acids in the synthesis, (iii) a lack of chemical stability, particularly in aqueous or humid environments, and (iv) adhesion and control in functional films and coatings. This Grant Opportunity for Academic Liaison with Industry (GOALI) award supports fundamental research to provide the knowledge needed to meet these challenges. This project involves new synthesis and processing avenues that enable the scalable nanomanufacturing of new MXene compositions while preventing degradation and new methods of controlled layer-by-layer assembly of MXenes in functional coatings. A special emphasis is placed on coating assembly features such as tunable optoelectronic properties. Additionally, education objectives include (1) mentoring undergraduate and graduate students alongside the GOALI industry partner, and (2) engaging the broader community via 2D nanomaterial-focused curriculum enhancements, a joint industry-government-academic workshop, and K-12 outreach. The technical approach to meeting the challenges with advanced manufacturing of MXene nanosheets includes experimental advances in their synthesis, etching, and assembly. In one objective, this project utilizes alternative etchants such as molten salt solutions for one-step HF-free synthesis of next-generation MXenes with a focus on how etchant type and etching conditions affect MXene yield, quality, and stability against chemical degradation. In another objective, this project creates layer-by-layer-assembled heterostructured functional coatings containing these next-generation MXenes. The focus of this objective is on the water-based solution assembly of MXenes into unique heterostructured coatings that contain precisely stacked regions of various MXene types with or without polymers. The manufacture of conformal coatings with alternating blocks of polymer and MXene allows for tailored optoelectronic properties leading to applications such as Shottky junctions, Bragg reflectors, and optical filters. In addition, this GOALI project has a partnership with Lynntech for added expertise in scalability of MXene production and advanced manufacturing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.