Local properties of a hydrated hydrogen intermediate of the electrochemical hydrogen reaction on Cu(100) have been studied on the all-electron ab initio level. In this first communication, several cuts on a multidimensional potential surface of chemisorbed hydrogen monohydrate and the partial charge transfer along these cuts have been considered. In the most favourable minimum-energy structure, HOH2 is chemisorbed in the hollow position, under destruction of hydronium configuration by strong elongation of the H(ad)-OH2 bond and rotation of the OH2 group into a H(ad)-HOH structure. In all hollow positions studied, the local charge on the intermediate is significantly negative. The electrochemical effect of partial charge transfer sequence on the dynamics of two-step hydrogen evolution on copper (valid also for other high-overvoltage metals) is discussed. Extension of the model by inclusion of a larger solvent environment of the adsorbate is outlined.
