LAUSR

ABSTRACT Manipulating the shapes of, otherwise flat, two-dimensional, 2D, flakes is important in many applications. Herein by simply decreasing the pH of a Ti3C2Tx MXene colloidal suspension, the 2D nanolayers crash out into crumpled flakes, resulting in randomly oriented powders, with a mesoporous architecture. Electrodes made with the latter showed capacities of 250 mAh g−1 at 20 mA g−1 in sodium-ion batteries. The rate performance, 120 mAh g−1 at 500 mA g−1, was also respectable. This acid-induced, reversible, crumpling approach is facile and scalable and could prove important in electrochemical, biological, catalytic, and environmental MXene-based applications. GRAPHICAL ABSTRACT IMPACT STATEMENT By simply decreasing the pH of a Ti3C2Tx colloidal suspension, we induce the 2D flakes flocculate into mesoporous crumpled flakes, that we then show can be used as Na-ion battery anodes.