Electrochemical etching of MXenes: mechanism, challenges and future outlooks

Transition metal carbides, nitrides and carbonitrides, commonly known as MXenes, are an astonishing class of two-dimensional materials, offering versatile surface chemistry, high electrical conductivity, tunable band gaps, and a unique layered morphology, which render them highly attractive for multiple applications ranging from energy storage and conversion to biomedical fields. However, recognising the true potential of MXenes demands precise regulation over their fabrication process and surface functionalization. Traditional MXene fabrication relies on HF acid and fluoride-based etching agents, which pose environmental and safety concerns, subsequently introduce defects and alter surface properties. Consequently, innovative fluoride-free strategies are garnering attention. This review focuses on the eco-friendly electrochemical etching strategy for MXene synthesis, which enriches the MXene surface with a variety of surface terminal groups, such as –O, –OH, and –Cl, varying the electrolyte and etching parameters including their cutting-edge advancements compared to the conventional strategy, highlighting the innovations, challenges, and future outlooks in MXene electrochemical synthesis.