The readiness of water molecules to split into hydrogen + oxygen: a proposed new aspect of water splitting.

The potential of the anode, at which the evolution of oxygen begins, is a key parameter that describes how well water is split in water electrolyzers. Research efforts related to electrocatalytically initiated water splitting that aimed at reducing the oxygen evolution reaction (OER) overpotential to date focused on the optimization of materials used to produce the electrodes. Descriptors for the readiness of the H 2 O molecule itself to break down into its components have not been considered in water electrolysis experiments so far. In a simple set of experiments, we found that adding dioxane to aqueous solutions leads to a substantial blue shift of the frequency of the O-H stretch vibration which is a sign for an increased strength of the O-H bond (intramolecular bonding). This phenomenon coincides with a significant increase of the OER onset potential as derived from cyclic voltammetry experiments. Thus, the O-H stretch frequency can be an ideal indicator for the readiness of water molecules to be split in its cleavage products. To our knowledge this is the first example of a study into the relationship between structural features of water as derived from FTIR spectroscopic studies, and key results derived from water electrolysis experiments. This article is protected by copyright. All rights reserved.