STUDIES OF THE MECHANISM AND KINETICS OF HYDROGEN ADSORPTION AND ABSORPTION

Methods for the determination of hydrogen adsorption, hydrogen evoluti on and hydrogen absorption were reviewed. Direct determination of the surface coverage by adsorbed hydrogen is possible only for the UPD hyd rogen and the surface coverage of the OPD hydrogen, involved in the hy drogen evolution reaction (HER), must be determined from the rate cons tants. However, determination of all the rate constants for the HER is possible only when their values are similar, which makes the determin ation of the surface coverage (OPD II) difficult. Studies of the HER o n Rh, Ru and Ni based electrodes shows that it proceeds via Volmer-Hey rovsky mechanism and the main contribution to the electrode activity c omes from the increase in the real surface area. Contrary to the HER, kinetics of the hydrogen UPD is very fast and difficult to determine. A general model of the hydrogen absorption in metals is proposed.