Moving from acridinium to pyridinium: From complex to simple. 2,4,6-Triphenylpyridine and 2,4,6-triphenylpyrilium perchlorate as 'metal-free' electrocatalysts of hydrogen evolution reaction (HER): The influence of the nature of the heteroatom and acid on the pathway HER

摘要

The electrocatalytic activity in the reaction of hydrogen evolution (HER) of new members of the family of metal-free electrocatalysts - 2,4,6-triphenylpyridine and 2,4,6-triphenylpyrillium perchlorate was studied. Using the method of cyclic voltammetry, preparative electrolysis and gas chromatography analysis the electrochemical behavior of electrocatalysts in the presence of acids of various strength (methanesulfonic, chloric, trifluoroacetic, acetic and triethylammonium hydrochloride) were studied. It has been shown that in the presence of chloric, methanesulfonic and trifluoroacetic acid, 2,4,6triphenylpyridine has a high catalytic activity (TOF 76, 66.3, 63.2, respectively), while 2,4,6-triphenylpyrillium perchlorate does not. In the presence of weak acids (acetic and triethylammonium hydrochloride), instead of the expected process of formation of mbolecular hydrogen, the main products of the cathodic electrochemical process were the formation of 2,4,6-triphenyl-1,4-dihydropyridine. The influence of the nature of a heteroatom on of a catalytic process is determined: it is shown that the stage of protonation of electrochemically generated radicals on the heteroatom is key in the electrocatalytic HER process. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.