This study represents the first important step towards a better understanding of the enhancement in the OER activity due to surface deprotonation and alkali metal cation adsorption on NiOOH. We speculate that this enhancement is linked with the stronger polarizability of the cations that increases with their size and thereby also leads to larger decrease in the work function upon specific adsorption. Experimental strategies have been proposed to enhance the OER activity of NiOOH-based materials by manipulating the work function through electron injection , which would support our speculation. However, we did not find stable specific adsorbate phases for the two largest cations K + and Cs + under operating conditions. Hence this change of the work function might also be caused by non-specifically adsorbed cations. Furthermore, it remains to be seen whether the direct interaction of the adsorbed alkali metal cations with the reaction intermediates of the OER also contributes to the enhancement.