Aminophenyl-substituted cobalt(iii) corrole: a bifunctional electrocatalyst for the oxygen and hydrogen evolution reactions

Abstract

Catalytic water splitting is a highly promising area of research for the development of a hydrogen-based society. Herein, the synthesis of the bifunctional A₂B-type cobalt(III) corrole Co(BAPC)Py₂ having the electron-withdrawing meso-pentafluorophenyl and the basic meso-p-aminophenyl substituents is reported. Cyclic voltammetric studies reveal that Co(BAPC)Py₂ has two oxidation waves at 0.97 V and 1.42 V associated with the Co(III) → Co(IV) and Co(IV) → Co(V) redox couples, respectively, and two reduction waves at 0.45 and −0.21 V corresponding to the Co(III) → Co(II) and Co(II) → Co(I) redox couples. The as-synthesized Co(BAPC)Py₂ corrole has been demonstrated to be an efficient catalyst for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in homogeneous (acetonitrile) as well as heterogeneous media. In a homogeneous solution, Co(BAPC)Py₂ showed excellent activity towards both the HER, with the first-order rate constant (k_cat) of 952.0 s⁻¹, and the OER with the first-order rate constant of 0.2 s⁻¹. The strong electron -withdrawing pentafluorophenyl group present on the corrole ring shifts the redox process towards the anodic direction and facilitates the HER performance, whereas the aminophenyl group increases the basicity of the catalyst that improves the OER activity.