Lewis acid molten salt synthesis of 2D MXenes with fine-tuned surface terminations for energy storage and conversion

Two-dimensional (2D) MXenes have gained substantial interest in energy storage and conversion technologies by virtue of their remarkable electrochemical properties. Traditional MXene synthesis methods involving hazardous acidic etchants pose safety concerns, scalability limitations, and yield MXenes with heterogeneous surface terminations which affect their suitability in specific energy applications. The emergence of Lewis acid molten salt (LAMS) method has revolutionized MXene synthesis by offering a safer, environmentally friendly, and more versatile approach that enables precise control over surface terminations. This review comprehensively summarizes the chemical synthesis of 2D MXenes and their hybrids using the LAMS method and modified approaches, along with recent developments of these rapidly evolving techniques within energy storage and conversion systems. Additionally, the advantages of the LAMS method beyond safety considerations in terms of fine-tuning surface chemistry, in-situ synthesis of metal/MXene hybrids, and expansion of the synthesis landscape are presented. Moreover, the strategies for delamination of LAMS-synthesized MXenes to obtain single/few-layer MXenes are also discussed. Finally, the review highlights the encountered challenges and proposes future perspectives.