Electrochemical Impedance Spectroscopy study of the preparation of electrocatalysts through galvanic displacement reactions

To explore the potential of Electrochemical Impedance Spectroscopy (EIS) in monitoring a galvanic displacement reaction, the deposition of Rh by displacement of Ni has been investigated, using both Ni disc electrodes of small size and Ni foam electrodes. The Ni dissolution/Rh deposition rate has been evaluated from EIS data and compared with values obtained by an independent method. The variation of the electrode double layer capacity with the reaction duration, caused mainly by the growth of Rh deposits, has been compared with the time dependence of the Rh surface area assessed by cyclic voltammetry (through the measurement of the H desorption charge). The quality of the agreement between different methods and possible reasons for discrepancies are discussed. It is shown that EIS may be a useful tool in the study of galvanic displacement processes.