抄録
The dynamics of the water molecules on a CO-covered Pt electrode has been studied by laser-induced potential transient measurements. This is a model system to elucidate the behavior of water molecules in the electric double layer during electrochemical reactions. At the potentials where CO is stably adsorbed, the Pt surface is negatively charged and water molecules are oriented pointing the hydrogen atoms toward the surface. The laser irradiation heats the interface and disturbs the orientation of water, which induces a potential jump toward the negative direction. We found that the amplitude of the potential jump on the CO-covered surface is much larger than on the CO-free surface. The finding suggests that the water molecules are more flexible on the CO-covered surface due to the weaker water-CO interaction than water-Pt interaction. Stronger laser pulse irradiation additionally induces the desorption of CO, which result in the adsorption of water with the hydrogen atom pointing toward the surface and induces a positive potential shift. The potential shift takes ∼70 microseconds to reach the maximum, which becomes slower as the electric field becomes intense. The intense field and hydrogen-bonded cations affect water structure in a long range and the collective motion of the water layers.
