Three-dimensional MXenes heterostructures and their applications

Due to their unique surface chemistry, highly adjustable metal components, hydrophilicity, and high carrier concentrations, MXenes are applied in a variety of scenarios. Similar to other two-dimensional (2D) materials, building heterostructures with additional materials to form a 3D porous architecture for MXenes can significantly enhance their functionality and reactivity. Notably, the open structures and well-defined pathways of these 3D structured MXenes can improve ionic and electronic transport, thereby promoting their applications in electrochemical energy storage, sensing, catalysis, and environment. In this review, the recent efforts made on preparing 3D porous MXenes with heterostructures, focusing on MXenes/C, MXenes/inorganics, and MXenes/polymers were summarized. The discussion covers aspects ranging from the design to synthesis of 3D porous MXenes, and their applications in photocatalysis, environmental monitoring and electrochemical energy storage. This review is concluded by presenting the prospects and insights on exploring the relationships between the porosity formation mechanisms, properties and applications of the 3D porous MXenes heterostructures. This review can provide meaningful guidance for the design, fabrication and application of 3D porous MXenes in high-performance materials and devices.