Expedited Electrochemical Activation of Cobalt Metal–Organic Frameworks via Undercoordination Chemistry for Robust Bifunctional Electrocatalytic Oxygen Evolution Reaction and Hydrogen Evolution Reaction

Abstract

The development of highly active and stable bifunctional transition metal-based electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a critical challenge in the pursuit of renewable and clean energy. Metal centers have emerged as pivotal components in optimizing the electronic structure and enhancing catalytic activity for electrocatalysis. In this work, we present a Cobalt-based metal–organic framework (Co-MOF) featuring two metal centers, bridged by oxygen, as confirmed by single-crystal X-ray diffraction. Further, Co-MOF was activated electrochemically (aCo-MOF) by uncoordination chemistry, removing one organic ligand from the metal center, making a mixed valence (Co2+/Co3+) environment in the metal node. This process alleviates spatial hindrance, facilitating intimate contact between hydroxide species and metal active centers, thereby enhancing the catalytic efficiency for OER and HER. We have explored the synthesis strategies, structural characteristics, and electrochemical properties of MOF, highlighting their applications for HER and OER. The catalyst (aCo-MOF) delivered an overpotential of 284 mV for OER and 148 mV for HER, at the current density of 10 mA cm2. This exploration is crucial for advancing MOF-based catalysts for electrocatalytic applications and for guiding the future design of more effective catalysts. © 2025 Elsevier B.V., All rights reserved.