In general, based on studies in other electrolytes, the following aspects might as well have to be considered for assessing the quality of an IL electrochemically. While it seems clear that the electrochemical response is related to the quality of the electrode and the electrolyte, the role of species dissolved from components which are in touch with the electrolyte (i.e., cell, reference or counter electrode) must be considered. Also, note that in our case, the complete removal of water is presumably almost impossible since a water film can form on the Au(111) electrode after its preparation under laboratory conditions and during the transfer into the glove box. Aside from the additional features observed in the CV related to Na, the CVs did not significantly change upon removing water from the IL. In contrast, previous reports clearly illustrated the impact of water addition or removal on surface redox processes. 15-17 However, for electro- (black) and the molecular sieve-dried IL (blue), and the poly-crystalline gold sheet after polarisation at -1.8 V in the molecular sieve-dried IL for 2 h (red) in the Na 1s region. chemical processes in ILs which involve reactive species, such as metal deposition or oxygen reduction, water certainly has a critical influence.