AlCl₄^--Intercalation Driven Molten Salt Electroetching with Closed-Loop Al Recovery

Conventional MXene synthesis relies heavily on hazardous etchants, necessitating the development of environmentally benign alternatives. We present a sustainable molten salt electroetching strategy using a LiCl-KCl-AlCl₃ electrolyte that selectively extracts Al from the V₂AlC MAX phase at the anode while simultaneously depositing metallic Al at the cathode, establishing a closed-loop, self-balanced system. Systematic optimization identified 2.2 V as the critical potential, enabling efficient Al dissolution (30% over 800 cycles) while preserving intact V₂C MXene layers; in contrast, 2.1 V resulted in sluggish etching (<10%) and 2.3 V caused overetching with carbide-derived carbon formation. Kinetics analysis revealed that AlCl₄^- intercalation into the expanding V₂C interlayers dynamically enhances the etching rate, evidenced by the progressively increasing AlCl₄^- diffusion coefficients during the process. This electroetching approach provides a sustainable and efficient pathway for MXene fabrication.