Potential-Dependent Water Orientation on Pt(111), Pt(100), and Pt(110), As Inferred from Laser-Pulsed Experiments. Electrostatic and Chemical Effects

The laser-induced temperature jump method is used to characterize the net orientation of interfacial water on well-defined platinum surfaces, Pt(111), Pt(100), and Pt(110), as a function of the applied potential. A clear effect of the surface structure on the potential of water reorientation is observed, being 0.37 for Pt(111), 0.33 for Pt(100), and 0.14 V vs RHE for Pt(110) in 0.1 M HClO(4) solution. The potential of water reorientation also exhibits a different pH dependency for the three basal planes, shifting 0.060 for Pt(111), 0.030 for Pt(100), and 0.015 V/dec for Pt(110). Comparison with charge density data provides a deeper understanding of these results. A quantitative analysis of the electrostatic and chemical effects governing the potential-dependent reorientation of the interfacial water network is addressed. It is concluded that water on Pt(111) exhibits a small net orientation in the absence of electric field at the interphase. On the other hand, the agreement between the relative position of values of the potential of water reorientation and work functions, for the three basal planes, suggests that the same situation holds for Pt(100) and Pt(110).