Strategies for engineering the MXenes toward highly active catalysts

Two-dimensional (2D) transition metal carbides, nitrides and carbonitrides (MXenes) have been extensively studied in catalysis due to their high specific surface area, favorable electrochemical properties, excellent corrosion resistance, high mechanical strength, superior electrical and thermal conductivity. Additionally, the unique 2D features with adjustable surface properties of MXene enable its structure to be engineered as catalyst towards a range of the electro-, photo- and thermal-catalytic reactions. In this review, we summarize the advanced engineering strategies that have been developed for MXenes to achieve desirable catalytic performance, including termination engineering, atomic engineering, interfacial engineering and hybrid engineering. We focus on disclosing the origin of enhanced catalytic activity realized by different engineering strategies from the mechanism perspective. Then the limitations and challenges of MXenes engineering under various conditions are discussed. Furthermore, some advanced in situ techniques are recommended to elucidate the active sites in MXenes. Finally, we point out the future directions in MXenes engineering towards highly active catalysts at industrial standard.