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 RhIII at lower potentials and RhIV 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.