Salient electrochemical and electrocatalytic behaviour of the crown heteropolyanion K28Li5H7P8W48O184·92H2O

The crown heteropolyanion K28Li5H7P8W48O184·92H2O is stable in a large pH domain, roughly from 0 through pH 8. Its electrochemistry proceeds through three successive, 8-electron reduction waves when the pH is chosen to avoid proton discharge before the third one. All of them are chemically reversible on the timescale of slow scan cyclic voltammetry. It is found that an inversion of acidity exists between at least two of its reduced intermediates. The numerous possibilities of electrocatalytic processes opened up by the electrochemistry of this oxometalate are exemplified here by the reduction of nitrite and nitric oxide. For nitric oxide, it appears that the catalytic reduction is strongly enhanced by trace amounts of dioxygen.