Exploring the oxygen evolution electrocatalysis of an amine-based cobalt metal–organic framework

Abstract

When immobilised on a suitable electrode surface, metal organic frameworks (MOFs) can effectively promote the oxygen evolution reaction (OER) – the anode process of water electrolysis for the green hydrogen synthesis – most commonly through the electrooxidative decomposition of the framework into thermodynamically stable (oxy)hydroxides/oxides. In this study, the potential advantageous electrocatalytic effect of the macrocyclic amine core coordinating to the cobalt ions in an interdigitating 2D sheet framework is investigated. Nickel foam electrodes modified with Co-TMBT-MOF at a low loading of 0.25 mg cm⁻² (0.004 mmol_Co cm⁻²) sustained the OER rate of 20 mA cm⁻² (80 A g_MOF⁻¹) in 1 M KOH at ambient temperature at a stabilised overpotential of only 0.294 ± 0.005 V on a timescale of 20 h. Physical characterisation of the electrode after the OER tests confirmed transformation of the MOF into the catalytically active cobalt oxyhydroxide.