Electronic structure reading group - Arthur Hagopian

Water activation constitutes a key elementary step in several electrochemical reactions, including alkaline hydrogen evolution and acidic oxygen evolution. Yet, while electrocatalytic activity is commonly discussed in terms of adsorbed intermediates, considerably less is known about how an interfacial water molecule itself is brought into a sufficiently reactive electronic state before O–H bond cleavage and charge transfer. At electrified interfaces, this process may be strongly influenced by the instantaneous structure, electrostatic environment, and collective organization of the surrounding solvent.
In previous work, I proposed a mechanism in which collective alignment of water dipoles can shift water electronic levels sufficiently to enable reduction or oxidation of interfacial water, leading respectively to radical-anion- or radical-cation-like states. This mechanism was demonstrated for an idealized, ordered ferroelectric water layer. Here, I investigate whether the same physical picture survives in a realistic, thermally fluctuating electrochemical interface.
Using ab initio molecular dynamics and electronic-structure descriptors, I study Pt(111)/water interfaces under different interfacial charging conditions and in the presence of different electrolyte ions. I follow the energetic position of the water reduction and oxidation levels relative to the metal Fermi level and relate their fluctuations to the local solvent environment, including water orientation, dipolar correlations, and the interfacial local electrostatic potential.
More broadly, this work points toward a different way of looking at electrochemical interfaces. Rather than describing the interface solely through average quantities such as mean water orientation, average potential profiles, or static interfacial structures, I focus on the transient local configurations that continuously emerge from thermal fluctuations. Rare and short-lived solvent arrangements may create highly specific electronic environments that are largely invisible in ensemble averages, yet disproportionately important for reactivity. This perspective suggests that understanding electrochemical interfaces may require identifying not only their average state, but also the fleeting local states through which chemistry actually becomes possible.