Surface science lettersDetermination of the activation energy for OH desorption in the H2 + O2 reaction on Polycrystalline Platinum

We have investigated the temperature dependence of the desorption rate of OH produced in the oxidation of hydrogen on polycrystalline Pt by using laser induced fluorescence (LIF). Arrhenius type plots of OH desorption rates give quite straight lines, with an “apparent” desorption energy, EaOH, in the rang 1.4–2.3 eV depending on the relative hydrogen concentration. EaOH, differs from the “true” desorption energy, EdOH, due to the temperature dependence of the surface coverage of θOH,. Knowing θOH, from kinetic modelling calculation of this reaction we deduce EdOH, to be 2.0 ± 0.15 eV.