The kinetic study of the electrocatalytic hydrogen evolution reaction (HER) in the presence of the alpha-oximehydrazonate iron(II) bis-clathrochelates in different media (including aqueous solutions) with various H-acids as the source of H+ ions showed that the rate-limiting stage of such electrocatalytic 2H(+)/H2 reaction is the protonation of two encapsulated electrochemically generated iron(I) metallocenters and the general kinetic scheme of this process persists irrespective of a source of H+ ions. (C) 2014 Elsevier Ltd. All rights reserved.