Unexpected the Mechanistic Pathway of the Hydrogen Evolution Reaction in the Presence of N‐Substituted Hydro‐Derivatives of <i>Ortho</i>‐Bipyridines

ABSTRACT Using cyclic voltammetry, the electrochemical properties and electrocatalytic activity in the reaction of molecular hydrogen formation in the presence of 2,2′‐bipyridinium‐1,1′‐diium and 2,2′‐bipyridinium‐1‐ium perchlorates were studied. The electrochemical reduction product of 2,2′‐bipyridinium‐1,1′‐diium perchlorate decomposes to form molecular hydrogen, but in the case of 2,2′‐bipyridinium‐1‐ium perchlorate, a two‐electron reduction product is formed −(E)‐1H,1′H‐2,2′‐bipyridinylidene. It has been shown that the hydrogen evolution reaction (HER) in the presence of 2,2′‐bipyridinium‐1,1′‐diium and 2,2′‐bipyridinium‐1‐ium perchlorates occurs at the same potentials but through different mechanisms. In both cases, the potential is −0.85 V according to the CECE mechanism, but at a potential of −1.25 V according to the ECEC mechanism. In both cases, the key intermediate, through which both mechanisms are realized, is (E)‐1H,1′H‐2,2′‐bipyridinylidene.