Hidalgo Acosta, Jonnathan CesarScanlon, MicheálMéndez, Manuel AlejandroPeljo, PekkaOpallo, MarcinGirault, Hubert2016-06-032016-06-032016-06-03201610.1002/celc.201600190https://infoscience.epfl.ch/handle/20.500.14299/126448WOS:000390800900006The water oxidation process in acidified water/acetonitrile mixtures was studied by cyclic voltammetry using fluorinated tin oxide (FTO) electrodes modified layer-by-layer with deposited bilayers of positively charged poly(diallyldimethylammonium chloride) (PDDA) polymer and negatively charged citrate-stabilized iridium oxide (IrO2) nanoparticles. The voltammetric profiles obtained at high water contents resemble those in aqueous media and remain approximately unchanged. However, as the water content decreases below a water mole fraction (XH2O) of 0.6, a tipping-point is reached and the onset potential for water oxidation gradually decreases. This reflects an enhanced reactivity, and therefore lower overpotential, of water molecules towards oxidation in water/acetonitrile mixtures. These lower kinetic barriers towards water oxidation are rationalized based on the degradation of the hydrogen bond network upon the formation of water/acetonitrile mixtures. Thus, as the ice-like structure of neat water transitions to clusters and low-bonded oligomers, these water molecules in more "free" states exhibit an enhanced susceptibility to water oxidation.iridium oxidelayer-by-layer assemblynanoparticleswater oxidationwateracetonitrile mixturestext::journal::journal article::research article