Figure schematically shows the setup of the reaction. A graphite crucible was used as the reaction container and the current collector for the MAX phase powder. This approach allowed the etching of the MAX phase in its powder form without using a binder, as all MAX phase settled at the bottom of the graphite crucible during the etching process. Pt wire was used as the cathode. However, it is worth mentioning that the etching can also be carried out with graphite as the counter electrode, which suggests that the hydrogen evolution does not have to occur on the surface of platinum. For the electrochemical etching, the mechanism was proposed as follows: