1,3-Dimethyl-2-phenyl-1Н-benzo[d]imidazolium Iodide—A Representative of a New Class in the Family of Metal-Free Organic Catalysts: Electrochemical Properties and Electrocatalytic Activity in the Reaction of Formation of Molecular Hydrogen

The electrochemical properties and electrocatalytic activity of 1,3-dimethyl-2-phenyl-1 H -benzo[ d ]imidazolium-3 iodide ( I ), a representative of a new class of organic metal-free electrocatalysts, in the reaction of formation of molecular hydrogen, in the presence of acids of various strengths (methanesulfonic acid (CH 3 SO 3 H), perchloric acid (HClO 4 ), and trifluoroacetic acid (CF 3 COOH)) have been studied. It is shown that the efficiency of the electrocatalytic process strongly depends on p K a of the acids used. Using gas chromatography and preparative electrolysis at half-wave potentials, it was shown that molecular hydrogen formed with high Faraday yields in all cases. The behavior of the catalytic wave on the cyclic voltammogram (CV), at various ratios of acid and catalyst concentrations in the presence of all acids is typical for the process proceeding according to a homogeneous mechanism. The mechanism of the process was studied by the density functional method (DFT), and its main intermediates were identified. The protonation of electrochemically generated radicals at the C-2 carbon atom of compound I , with the formation of a C-protonated radical cation, was shown to be the key stage of the electrocatalytic hydrogen evolution reaction (HER).