2D transition metal dichalcogenides, carbides, nitrides, and their applications in supercapacitors and electrocatalytic hydrogen evolution reaction

The development of renewable energy conversion and storage devices, aiming at high efficiency, stable operation, environmental friendliness, and low-cost goals, provides a promising approach to resolve the global energy crisis. Recently, two-dimensional (2D) layered materials have drawn enormous attention due to their unique layered structure and intriguing electrical characteristics, which brings the unprecedented board applications in the fields ranging from electronic, optical, optoelectronic, thermal, magnetic, quantum devices to energy storage and catalysis. Graphene-based 2D layered materials show promising applications in energy storage and conversion owing to their high specific surface area, which have been used for supercapacitor electrode materials based on the electrical double-layer capacitance model. However, graphene has a limited value of theoretical electrical double-layer capacitance when the whole surface area is fully utilized. Among several classes of 2D layered materials beyond graphene, transition metal dichalcogenides, transition metal carbides, and nitrides may exhibit excellent electrochemical properties due to the distinctive features of these 2D materials, such as large specific surface area, good hydrophilic nature, highly exposed active edge sites, and ease of intercalation and modification. Therefore, careful design and construction of these 2D compounds make them become potential candidates used for electrochemical supercapacitors and electrocatalytic hydrogen evolution. This review emphasizes the recent important advances of the 2D layered materials composed of transition metal dichalcogenides, transition metal carbides, and nitrides for supercapacitors and electrocatalysts. Furthermore, we discuss the challenges and perspectives in this energy field in terms of the classes of two-dimensional layered materials.