Despite prolonged scientific efforts to unravel the effects of ions on the structure and dynamics of water, many open questions remain, in particular concerning the spatial extent of this effect (i.e., the number of water molecules affected) and the origin of ion-specific effects. A combined terahertz and femtosecond infrared spectroscopic study of water dynamics around different ions (specifically magnesium, lithium, sodium, and cesium cations, as well as sulfate, chloride, iodide, and perchlorate anions) reveals that the effect of ions and counterions on water can be strongly interdependent and nonadditive, and in certain cases extends well beyond the first solvation shell of water molecules directly surrounding the ion.

Nonaqueous lithium–air batteries have garnered considerable research interest over the past decade due to their extremely high theoretical energy densities and potentially low cost. Significant advances have been achieved both in the mechanistic understanding of the cell reactions and in the development of effective strategies to help realize a practical energy storage device. By drawing attention to reports published mainly within the past 8 years, this review provides an updated mechanistic picture of the lithium peroxide based cell reactions and highlights key remaining challenges, including those due to the parasitic processes occurring at the reaction product–electrolyte, product–cathode, electrolyte–cathode, and electrolyte–anode interfaces. We introduce the fundamental principles and critically evaluate the effectiveness of the different strategies that have been proposed to mitigate the various issues of this chemistry, which include the use of solid catalysts, redox mediators, solvating additives for oxygen reaction intermediates, gas separation membranes, etc. Recently established cell chemistries based on the superoxide, hydroxide, and oxide phases are also summarized and discussed.

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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).