Electrochemical Investigation of Non-equilibrium Surface States of Matter

High energy, non-equilibrium, surface states of metals, which are assumed to be associated with surface defect sites, have not received a great deal of attention in surface electrochemistry. Such states, which are assumed to be the basis of active site behaviour, are minority surface species which display redox (or faradaic) behaviour that is quite different from the conventional response of the majority surface state, i.e. similar atoms present in equilibrated form at the same surface. The effect of enhancing the coverage of the high energy surface state is illustrated, as is the role of such states in electrocatalysis, plating bath additive behaviour and the operation of metastable metal oxide electrodes such as ruthenium dioxide cathodes. Non-equilibrium surface states are difficult to control and investigate as they evidently involve quite low coverage, rather labile, surface species which are not easily imaged by STM.