Electrochemical studies of vitamin K1 microdroplets:: Electrocatalytic hydrogen evolution

The voltammetry of a basal-plane pyrolytic graphite electrode modified with a random ensemble of unsupported microdroplets of vitamin K-j is investigated when the electrode is immersed in aqueous electrolytes. It is shown that in dilute acidic solutions; electroreduction occurs in a single two-electron two-proton process to yield the corresponding hydroquione at the electrode vitamin K-j microdroplet/aqueous-electrolyte, three-phase boundary. On addition of ionic alkali-metal salts to the aqueous acidic phase, the electrochemical reduction of vitamin K-j to the quinol is accompanied by catalytic hydrogen evolution within and alkali-metal-cation insertion into the organic microdroplets in strongly alkaline solutions, electrochemical reduction of vitamin K-j at the triple phase junction is proposed as being a single two-electron process with concomitant uptake of alkali-metal cations in order to maintain electroneutrality within the oil phase is demonstrated to be governed by the degree of ion-pair formation rather than by the Gibbs transfer energy of the cation across the liquid/liquid interface.