Boosting Electrocatalytic Activity of Bimetallic CoNi-MOF for OER and HER Through a Synergistic Bimetallic Approach.

Due to the decreasing availability, reduced stability, and high cost of noble metal-based catalysts, the search for stable, efficient, and inexpensive electrocatalysts is of significant importance. In this study, three new isostructural Co(II), Ni(II), and CoNi metal-organic frameworks (MOFs) based on bis-coordinating ligand 3-pyridyl acrylic acid are explored as efficient electrocatalysts. The structure of CoNi-MOF was further confirmed by various experimental techniques. The electrocatalytic activities toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) revealed that the bimetallic CoNi-MOF demonstrated significantly greater activity towards OER and HER compared to its monometallic counterparts, Co-MOF and Ni-MOF. CoNi-MOF requires 350 mV and 150 mV overpotential to achieve a current density of 10 mA cm-2 for OER and HER, respectively. Moreover, they exhibited excellent stability for 6 hours and 1000 OER cycles, demonstrating its superiority in these reactions. The significant enhancement in the performance of CoNi-MOF is attributed to the bimetallic synergistic effects between the redox-active metal centers Co2+ and Ni2+, which increase the activity of the catalyst's surface, resulting in enhanced current density and reduced overpotential. The hydrogen bond between coordinated water molecules and un-coordinated carboxylate is essential for the electrochemical stability of the materials.