Electrochemical Exfoliation of Layered Non-van der Waals Crystals into 2D Nanosheets: MAX Phases and Beyond.

2D materials have rapidly gained attention due to their exceptional properties like high surface area, flexibility, and tunable electronic characteristics. These attributes make them highly versatile for applications in energy storage, electronics, and biomedicine. Inspired by graphene's success, researchers are exploring other 2D materials from bulk crystals. Electrochemical exfoliation (ECE) is an efficient method for producing these materials, offering more sustainable mild conditions, quick processing, simple equipment, and high yields. While substantial progress has been made in the ECE of layered van der Waals (L-vdW) crystals, the exploration of layered non-van der Waals (L-NvdW) materials remains in its early stages. This review delves into using ECE to create 2D nanoplatelets from L-NvdW crystals. A comparative analysis of exfoliation techniques is provided for L-vdW and L-NvdW materials, followed by a comprehensive overview of recent advances in ECE methods applied to L-NvdW crystals. The discussion is organized around key categories, including the selective extraction of "M" and "A" layers respectively from MAX phases, decalcification of Zintl phases, and oxide delocalization from metal oxides. It is concluded by highlighting the potential applications of these 2D materials and discussing the challenges and future directions in this evolving field.