X-ray photoelectron spectroscopic study of the rhodium electrode system in acid

Abstract

X-ray photoelectron spectroscopy has been used to investigate the surface of rhodium electrodes studied under steady-state and cyclic conditions in 0.5 mol dm^–3 sulphuric acid solutions. Steady-state polarisation of rhodium electrodes results in the formation of oxidised Rh^III at lower potentials and Rh^IV at higher potentials. The system is complicated by problems in the data analysis, caused by a Coster–Kronig transition between the metal 3d spin–orbit split components. This leads to an increase in the width of the 3/2 component compared with the 5/2 component. The carbon 1s spectra illustrate that CO is always present on a rhodium surface and that CO₂ is sometimes found. It is not clear whether the presence of the latter results from the electrochemical treatment or from adsorption from solution. Some electrochemical cleaning methods lead to oxidation.