Kinetics of hydrogen underpotential deposition at polycrystalline rhodium in acidic solutions

Kinetics of hydrogen underpotential deposition (H UPD) reaction at smooth polycrystalline rhodium wire has been studied in 0.1 M H2SO4 and HClO4 using cyclic voltammetry and electrochemical impedance spectroscopy. Real surface area of the Rh electrodes was determined by hydrogen adsorption method.For all impedance spectra registered at potentials corresponding to the H UPD deviations from the ideal capacitive behavior was revealed and a constant phase element was used instead of capacitance for description of Rh impedance behavior. Double layer and adsorption capacitances and charge transfer resistances of the H UPD were determined as functions of the electrode potential. It has been found that the kinetics of the H UPD reaction at Rh is slower than that at polycrystalline Pt but similar to that found at polycrystalline Ru. Slightly higher values of Rct were determined in perchloric acid.

► Hydrogen underpotential deposition on polycrystalline rhodium electrode in sulfuric and perchloric acids. ► Determination of the double layer and adsorption capacitances using impedance spectroscopy. ► Determination of the charge transfer resistance of H UPD as function of electrode potential using impedance spectroscopy.