With respect to the interpretation of cation effects in the HER Tafel region, there are two important contributions that should be taken into consideration: (1) The type of cations in the electrolyte seems to influence the transport of protons near the interface in alkaline environment (Fig. ). ( ) Different purity of the various cation salts used in the experiments will result in a varying amount and type of impurities on the Pt surface in different electrolytes.