Phase transformation of two-dimensional nanomaterials: state-of-the-art progress in designing strategies and catalytic applications

Phase transformation of two-dimensional (2D) nanomaterials can lead to significant changes in electronic and optical properties, which enables the development of novel applications. Effective strategies for phase engineering of 2D nanomaterials have drawn considerable attention in recent years. This review focuses on the state-of-the-art progress in the phase transformation of 2D nanomaterials and their catalytic applications. First, the basic concepts of phase transformation and the outstanding electronic and optical properties induced by phase transformation are briefly introduced. Second, different strategies for achieving phase transformation are discussed in detail and classified into several types based on their characteristics, including (i) doping, (ii) external fields, (iii) optical irradiation, (iv) strain effect, (v) high-energy particle excitation, and (vi) thermal post-processing. The applications of 2D nanomaterials in catalysis based on phase transformation have also been discussed. Finally, a summary of the technical challenges to phase control in 2D nanomaterials and potential opportunities for developing novel applications is presented.