In situ measurement of the rate of H absorption by a Pd cathode during the electrolysis of aqueous solutions

Abstract

An experimental setup to measure “in situ” the amount of H that a Pd cathode absorbs during the electrolysis of aqueous solutions has been built up and tested. The setup implements a volumetric technique, i.e., it involves the measurement of the rate of H2 generation by the cathode. The pros and cons of this type of techniques against other procedures, the measurement of the variation of the cathode electrical resistance or of its dilation during the electrolysis, are briefly discussed. A careful analysis of the setup error sources is done by using two non-H-absorbing Pt electrodes. Neither any significant recombination of the electrolysis gases (H2 and O2), nor any deviation of a 100% electrolysis efficiency have been observed. It has been found that gas (air) release and H2 and O2 absorption by the solution, in the first stage of the electrolysis, seriously affect the measurement of the rate of H absorption by the cathode. Several improvements of the experimental installation and an operation protocol of saturation of H2 and O2 and of exhaustion of air in the solution, before starting the electrolysis, allowed overcoming those limitations. Finally, we present the results obtained in the measurement of the rate of H uptake by a Pd cathode during electrolysis. The reliability of the measurement has been confirmed by electrochemically deloading the Pd cathode.