Upon integration of the current flow throughout the electrochemical etching process, each Ti3AlC2 crystal unit consumes 4.5 electrons (4.7 electrons for Ti3AlCN) when it is etched for 28 h at an etching temperature of 35 °C (calculation in supporting information). The value is expected to be slightly overestimated as part of the current flow may originate from the water electrolysis on the surface of the incompletely etched MXene. Yet, it concurs with the proposed mechanism that each aluminium requires 3 electrons for anodic dissolution, with the remaining 1.5 electrons contributing to the oxidation of the Ti3C2 surface.