Direct molecular dynamics and density-functional theoretical study of the electrochemical hydrogen oxidation reaction and underpotential deposition of H on Pt(1 1 1)

A combined direct molecular dynamics/density-functional theoretical study of the electro-oxidation of hydrogen at the Pt(1 1 1)/water interface has been carried out to provide insights into the reaction mechanism. The H2 oxidation proceeds via the Heyrovsky process – a heterolytic bond breaking brought about by the impinging hydrogen molecule striking the metal surface. The products are a hydrated H+ ion and a strongly adsorbed hydrogen atom lying nearly flat in a bridging position on the Pt(1 1 1) surface. The bridging H interacts only weakly with the aqueous phase of the metal/solution interface and imparts unique electronic and vibrational properties characteristic of underpotentially deposited H. Potential-dependent activation energies for the hydrogen redox reactions were evaluated.