Cyclic voltammetry was carried out to study the effect of voltage on the etching efficiency (Figure ). At 35 °C, the rise of current occurs around +0.8 V, indicating that this is the minimum voltage for triggering the electrochemical etching at that temperature. The CV curve mimics a typical capacitor-like shape due to the electrical double layer formed on the surface of the semi-etched MAX phases. It is worth noting that the minimal voltage (Vmin) required to trigger the electrochemical etching decreases as temperature increases (Vmin at 45 °C= 0.7 V, Vmin at 50 °C= 0.65 V). This coincides with the Nernst equation that reduction potential decreases as temperature increases. The fact that no current was detected in the control experiment when no MAX phase was present indicates that the flow of electrons is attributed to the redox reaction of the MAX phases with the electrolyte. Furthermore, it showed that HBF4 does not undergo other side reactions under the etching voltage. Nevertheless, the increase of voltage beyond +1 V would, in fact, decrease the etching efficiency, despite an increase of current being observed. This is because when the voltage applied exceeds +1 V, the current detected is no longer solely associated with the anodic dissolution of aluminum of the MAX phases but also from the water electrolysis. Also, vigorous gas evolution may disturb the MAX phases from settling at the bottom of the crucible and thus terminating the etching. Therefore, despite water splitting playing an important role in facilitating the electrochemical exfoliation of other 2D materials, such as graphene and MoS2, the vigorous evolution of gas on the surface of MAX phases only causes an isolation of the MAX phases surface from the electrolytes.