Molecular material based on electropolymerized cobalt macrocycle for electrocatalytic hydrogen evolution

Abstract : An electrocatalytic material for the H2 evolution reaction (HER) in acidic aqueous solution has been prepared by electropolymerization of Co(II) dibenzotetraaza[14] annulene (CoTAA). Chemical analysis by X-ray photoelectron spectroscopy (XPS) confirms that the structural integrity of the [CoII–N4] motif is preserved in the poly-CoTAA film. In acetate buffer solution at pH 4.6, an overpotential η = −0.57 V is required to attain a catalytic current density −ik = 1 mA cmgeom−2. The faradaic efficiency of poly-CoTAA for the HER is 90% over a period of one hour of electrolysis, but there is a decrease of the apparent concentration of Co sites after prolonged H2 production, which we ascribe to partial demetallation of the poly-CoTAA film at negative potentials.