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 7 (OH) 12 (C 2 H 4 S 2 O 6 )·1.6H 2 O was synthesized via a homogeneous alkalization reaction using Co(SO 3 C 2 H 4 SO 3 ) and hexamethylenetetramine. This compound comprises cationic host layers of {[Co 7 (OH) 12 ] 2+ } ∞ , which comprise octahedrally (Co Oh ) and tetrahedrally (Co Td ) coordinated Co cations at a Co Oh : Co Td 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 −2 ). In situ Raman spectroscopy showed that the sample first evolved into Co( iii )-based phases comprising a mixture of layered CoOOH and spinel Co 3 O 4 , and the Co( iii )-based compounds were converted into Co( iv )-O intermediates containing [CoO 6 ] units at the onsite of the OER. The structural evolution behaviors suggest that the catalyst prefers a topotactic phase transition and the Co Oh and Co Td 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. Layered cobalt hydroxide comprising octahedrally and tetrahedrally coordinated Co( ii ) at a ratio of 5 : 2 was synthesized to promote the oxygen evolution reaction.