Catalytic effect of under-potential deposited layers on the ferrous/ferric outer-sphere electrode reaction

Abstract

The influence of the electrode metal on the kinetics of outer-sphere redox reactions is still an unsettled question with contradictory results being re indicate the complete absence of an effect, while there is also experimental evidence that underpotential deposited (UPD) metal layers can influence th suggested that some of the reported catalytic effect may be experimental artifacts caused by anion adsorption on the electrodes. We have carried out a UPD-metal layers on the rate of the Fe 2+/Fe 3+ redox reaction on polycrystalline gold and platinum electrodes in perchloric acid solutions rigor with copper, silver, and bismuth UPD layers. Our experimental results indicate clearly that the catalytic effect of UPD-metal layers on outer-sphere re since the phenomenon persisted in rigorously purified solutions. We also suggest a possible theoretical explanation of this phenomenon. In a recent stu at a gold surface to be non-adiabatic, i.e. electronic coupling contributed significantly to the rate. In the work reported here we have investigated, effect observed for this reaction at a gold electrode with a UPD-copper monolayer may be due to changes in electronic coupling. We have found that, whi UPD-copper layer, the observed catalytic effect may still be due to a larger electronic coupling because the hydrated ion approaches closer to the UPD- electronic coupling and the rate of the reaction.