Hydrogen Evolution on Diamond Electrodes and Its Dependence on Surface C-H Bond Strengths

In this quantum chemical study it is shown that a hydrogen atom chemisorbs weakly to a surface carbon atom on hydrogen-terminated diamond (111) if there is a bond-inserted hydrogen atom, or a substitutional B atom, in the near-subsurface region. It is found that reductive hydronium ion discharge in the Volmer-Heyrovsky mechanism to form is activated over these adsorbed H atoms compared to the strongly bonded H that terminates the surface. Activation energies for generation are calculated for these systems as functions of electrode potential between 0 and , using constrained variation theory.