Other m/z peaks that are seen (e.g. M32-O2, and M40-Ar) relate to the small amount of air diffused to the electrolyte (due to the EC-MS cell configuration, seeing air is unavoidable) but will not influence the phenomena that are being discussed. M2 in the absence of H2 formation stems from interstitial H2 leaking out from the stainless-steel components in the system. Nevertheless, the IM2 in the absence of H2 formation is so low that it is regarded as the system background. The over 400 times increment at M2 with H2 formation is more than enough to serve as the indicator for H2 molecules produced from the electrochemical reaction. Details of the system configuration can be found in .