Preparation And Electrochemistry Of Iron, Ruthenium, And Cobalt(Ii) Hexaphenanthrene Clathrochelates Designed For Efficient Electrocatalytic Hydrogen Production And Their Physisorption On Carbon Materials

Transition metal clathrochelates are promising electrocatalysts of the hydrogen evolution reaction, for example at the cathodes of water electrolysers. Their electrochemical activity can be maximized by forming monolayers on a surface of electrode materials of large specific area, such as carbon powders or fibers. Surface functionalization via physisorption is the easiest way to implement these electrocatalysts. This process can be improved by increasing the number of polyaromatic groups per a cage molecule of these complexes. We performed the synthesis and characterization of three novel iron, ruthenium and cobalt(II) clathrochelates, containing six terminal polyaromatic groups each. Their chemical composition and macrobicyclic structure were determined using MALDI-TOF MS, UV-Vis, H-1 and C-13{H-1} NMR spectra. The cyclic voltammograms of these three complexes and of their hexachloromacrobicyclic precursors were recorded in dichloromethane solutions, using glassy carbon and platinum as working electrodes, over the 10-100 mV.s(-1) range of potential scan rate. The physisorption isotherms of these three complexes, on three different carbon materials of practical interest for their application at the cathodes of water electrolysers (activated carbon, reduced graphene oxide and carbon paper) were measured in dichloromethane - acetonitrile solutions using UV-vis spectrophotometry. The thermodynamic parameters of the sorption processes were calculated. (C) 2019 The Electrochemical Society.