Review—The Oxygen Reduction Reaction on MXene-Based Catalysts: Progress and Prospects

The oxygen reduction reaction (ORR) is a critical, but sluggish reaction used for various applications, including fuel cells and metal-oxygen batteries. Currently, the benchmark catalysts for ORR are Pt-based catalysts. However, due to these catalysts being scarce and very expensive, alternative catalysts that are more abundant and less expensive are urgently in demand. MXenes, a new two-dimensional (2D) material based on transition metal carbides and nitrides, have advanced the performance of many existing technologies, including batteries, supercapacitors, sensors, etc. Owing to their unique electronic structure, physical and chemical properties, and tunable morphology, MXenes are expected to thrive in the ORR electro- and photo-catalytic systems. Recent studies reported better-performing ORR catalysts with MXenes as supports, which holds promise in the significant reduction of Pt loading for efficient catalysts. Furthermore, MXenes exhibit wide applicability and stability in a range of pH values, from acidic to basic. In this work, we carefully review the most pertinent works on ORR using MXenes. We first discuss the catalytic performance of MXenes in alkaline and acidic environments, followed by their application in metal-air batteries. We investigate the gaps and challenges in the field, identify key areas that need further attention, and provide directions for future research.