Hydrogen production with a designed clathrochelate-based electrocatalytic materials: Synthesis, X-ray structure and redox-properties of the iron cage complexes with pendant (poly)aryl-terminated ribbed substituents

Abstract Cage iron(II) complexes with one, two or six terminal (poly)aromatic group(s), designed for effective physical adsorption on the carbonaceous substrates, were prepared by nucleophilic substitution of their mono-, di- and hexachloroclathrochelate precursors with 3-arene-1(9)-yl-propane-1 thiolate anions. Their cyclic voltammograms contain the single Fe 2+/+ reduction wave in the cathodic potential range and two oxidation waves in the anodic potential range, assigned to a metal-centered Fe 2+/3+ process and to oxidation of their arylalkylsulfide groups, respectively. Iron(II) hexaphenanthrenylsulfide clathrochelate with six terminal polyaromatic groups was either immobilized or impregnated on the cathode of gas diffusion electrode and its electrochemical activity with regard to hydrogen evolution reaction (HER) was tested in a proton exchange membrane water electrolysis cell for hydrogen production. It was shown that effective immobilization of this (pre)catalyst on the surface of appropriate carbonaceous electrode materials can be successfully used for improving an efficiency of clathrochelate-based hydrogen-producing systems.