Tailoring Electrochemical Water Oxidation Activity from the Isostructural Series of Alkaline-Stable Bimetallic Fe,Ni-Azolate Metal-Organic Frameworks

Incorporating electrocatalytic active sites into the reticular framework allows for the design of novel catalytic structures promoting desired catalytic reactions with efficient mass transfer. However, to fully exploit the advantages of such a framework, it is crucial to ensure the electrochemical stability of the material. In this context, alkaline-stable bimetallic MxNi2-xCl2BTDD (M = Fe, Co) metal-organic frameworks (MOFs) are employed as electrocatalysts for alkaline water oxidation reaction (WOR) to understand the correlation between secondary metal incorporation and catalytic activity changes. For a specific Fe ratio within the MOF, the optimal catalytic activity is achieved at an overpotential of 315 mV at a WOR current density of 10 mA cm-2geo. Based on its well-defined crystal structure and uniformly arranged metal nodes, which are not limited to specific facets, the cooperative electrocatalytic mechanism during the faradaic WOR process is investigated through operando Raman spectroscopy and density functional theory calculations. These results enable the interpretation of the electrochemical WOR mechanism based on MOF, providing a further fundamental understanding of electrocatalytic activity in bimetallic systems. Utilizing MxNi2-xCl2BTDD (M = Fe, Co) metal-organic frameworks as catalysts for the electrochemical alkaline water oxidation reaction, the focus is on comprehending the role of secondary Fe, which exhibits optimal catalytic activity at the molecular level. Operando Raman analysis, coupled with density functional theory calculations, enables a more intuitive analysis of the synergistic effect between Ni and Fe. image