Enthalpy and entropy of oxygen electroadsorption on RuO 2 (110) in alkaline media.

We report the temperature influence of the OH _ad and O _ad electroadsorption on RuO ₂ (110) films grown on TiO ₂ (110) crystals in alkaline media. From the temperature effect, we evaluate the enthalpy and entropy of the OH _ad and O _ad electroadsorption, including the adsorbate-adsorbate interactions that we analyze using the interaction parameters of the Frumkin-isotherm model. We found that the adsorbates repel each other enthalpically but attract each other entropically. Our result suggests that an entropy analysis is necessary to capture the electroadsorption behavior on RuO ₂ since the enthalpy-entropy competition strongly influences the electroadsorption behavior. Our observation of an entropic force is consistent with the view that water may be a mediator for adsorbate-adsorbate interactions.