Applications of MXene-Based Single-Atom Catalysts

Single-atom catalysts (SACs) consist of isolated metal sites on the support through stable coordination bond, which usually have high catalytic activity and selectivity. With large surface area and electron tunability, metallic carbides, nitrides, or carbonic nitrides (MXenes) are suitable carriers for supporting isolated single-metal atoms. The abundant surface-functional groups and vacancy defects on MXenes are the ideal anchoring sites for isolated metal atoms. Herein, the advanced synthesis and characterization methods for MXene-based SACs are first introduced. Three strategies (adsorption at functional groups, anchoring at metal vacancies, and anchoring at surface terminating group vacancies) appear to be feasible in ensuring the non-aggregation of single-metal atoms, which are attributed to the strong bonding between the single-metal atoms and the carrier. The applications of MXene-based SACs in electrocatalysis (including hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and nitrogen reduction reaction), energy storage (including Li-ion batteries, metal-air batteries, and supercapacitors), and sensors (including gas sensors and biological sensors) are fundamentally reviewed. Finally, own insight on the current challenges and prospects of MXene-based SACs is presented.