Enthalpy and entropy of oxygen electroadsorption on RuO2(110) in alkaline media.

We report the temperature influence of the OHad and Oad electroadsorption on RuO2(110) films grown on TiO2(110) crystals in alkaline media. From the temperature effect, we evaluate the enthalpy and entropy of the OHad and Oad 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 RuO2 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.