Synthesis of ethane-disulfonate pillared layered cobalt hydroxide towards the electrocatalytic oxygen evolution reaction.

We report the synthesis of a hybrid layered cobalt hydroxide sample and its redox behaviors in the electrochemical oxygen evolution reaction (OER). Compound Co(OH)(CHSO)·1.6HO was synthesized a homogeneous alkalization reaction using Co(SOCHSO) and hexamethylenetetramine. This compound comprises cationic host layers of {[Co(OH)]}, which comprise octahedrally (Co) and tetrahedrally (Co) coordinated Co cations at a Co : Co ratio of 5 : 2. The ethane-disulfonate ions are combined with the cationic host layers by electrostatic attractions and hydrogen bonding as a hybrid pillared layered framework. This hybrid sample can promote the OER in 1 M KOH with an overpotential as low as ∼410 mV (at a current density of 10 mA cm). Raman spectroscopy showed that the sample first evolved into Co(III)-based phases comprising a mixture of layered CoOOH and spinel CoO, and the Co(III)-based compounds were converted into Co(IV)-O intermediates containing [CoO] units at the onsite of the OER. The structural evolution behaviors suggest that the catalyst prefers a topotactic phase transition and the Co and Co units exhibit different activities in the electrochemical reaction. The electron transfer events involved in the electrochemical reaction were identified by Fourier-transformed alternating current voltammetry.