Bimetallic Conductive Metal Organic Framework Nanorods with Atomically Dispersed Fe and Co Sites for Efficient Oxygen Evolution

Abstract

Exploring efficient nonpyrolysis conductive metal organic frameworks with high intrinsic reactivity is critical for their application in the electrocatalytic field. Herein, we present electronically conductive π-d-conjugated Co and Fe bimetallic MOF-CoFe-hexahydroxytriphenylene (CoFe-HHTP) nanorods with atomically dispersed Co–O₆ and Fe–O₆ sites for efficient oxygen evolution reaction (OER) catalysis. The introduction of Fe not only increases the electronic conductivity of Co-HHTP with an order of magnitude favoring the electronic transfer during OER catalysis but also tailors the electronic structure of Co, leading to a downshift of Co d-band center that weakens the adsorption of oxygen intermediates on Co sites. As a result, the as-prepared CoFe-HHTP exhibits a significantly improved OER activity showing a lower overpotential (316 mV) at a current density of 10 mA cm^–2 in an alkaline electrolyte compared with pure Co-HHTP (370 mV), outperforming commercial RuO₂ (329 mV). CoFe-HHTP also displays a superior electrochemical durability with only a slight change of potential after a 200 h test at 10 mA cm^–2, outperforming pure Co-HHTP (140 h). The improved durability was due to the hindered dissolution of Co by suppressing structural transformation in the presence of Fe in the alkaline electrolyte. When CoFe-HHTP was used as the anode catalyst, a superior alkaline electrolyzer performance was obtained with a cell voltage of 1.821 V at 500 mA cm^–2 and a stable operation of 50 h. This methodology offers insights into the design and synthesis of conductive MOF-based catalysts for efficient OER catalysis.