УДК 544.651.23 Vladimir L. Krasikov1 A NEW APPROACH TO THE MECHANISM OF HYDROGEN EVOLUTION REACTION ON RHENIUM: 3D-RECOMBINATION JSC Russian Institute of Radionavigation and Time, pl. Rastrelli, 2, St. Petersburg, 191124, Russia. e-mail kras257@km.ru In this analytical paper we have viewed the characteristics of cathodic hydrogen evolution reaction on electrodeposited rhenium in acid media with hydrogen atoms recombination as a limiting stage. <...> We came to the conclusion that a part of forming adsorbed hydrogen atoms penetrates into the metal subsurface layer thus releasing the rhenium surface for the following hydroxonium ions discharge on the same spot. <...> Thereafter the recombination of atoms adsorbed on the surface and atoms absorbed in the bulk of metal proceeds with hydrogen molecule formation. <...> According to the presented model of the three-dimensional recombination the rhenium surface is never filled with adsorbed hydrogen entirely which explains why the recombination limiting current is not observed experimentally. <...> A similar process scheme may be applied for the explanation of cathodic hydrogen evolution on many metals and alloys able to absorb hydrogen. <...> We showed that in order to explain the regularities of cathodic hydrogen evolution on metals it is necessary to take into account the atomic hydrogen mass transfer on the surface and in the bulk of metals. <...> DOI 10.15217/issn1998984-9.2016.34.24 Recently we observe an increased interest in rheIntroduction nium, its alloys and compounds behavior that is, in particular, cathodic hydrogen evolution on rhenium. <...> Cathodic hydrogen evolution on electrodeposited rhenium is peculiar in the following way. <...> First, rhenium electrodeposition from, for instance, SO4 the electrolyte of KReO4 – 12 g/l, H2 perature of 60◦ C and the current density of 400 mA/cm2 – 35 g/l at the temis accompanied by intensive hydrogen evolution, rhenium current efficiency amounts to only 7.4% [1], that is the largest part of the current is spent on hydrogen evolution. <...> After rhenium electrodeposition and current cut-off we can still observe hydrogen evolving on electrode as if the current was not switched off. <...> Such hydrogen evolution can last for several tens of seconds but still it is determined not by rhenium dissolution in acid deposition electrolyte, but by hydrogen desorption <...>