Electrochemical Transformation of Ni-based Metal-Organic Frameworks: An in-situ Raman spectroscopy study.

Metal-organic frameworks (MOFs) are emerging as promising materials for catalytic water splitting. A growing body of research suggests that they serve as pre-catalysts, undergoing an electrochemical transformation into layered double hydroxide (LDH) phases. These LDHs exhibit superior activity for the oxygen evolution reaction (OER) compared to directly synthesized LDHs. By combining in-situ Raman spectroscopy with electrochemical testing, we explore how water molecules at the material’s interface influence these transformations. We examine 2D and 3D MOFs synthesized using diverse methods, different organic linkers and containing different metal doping, to uncover how the hydrogen bonding of the interfacial water correlates with changes in catalytic performance. For example, we observed that catalysts synthesized with 2-methylimidazole transform at a faster rate than those with terephthalic acid, which aligns with variations in interfacial water hydrogen bonding. In addition, we tracked the evolution of the active NiOOH phase, noting changes in water structure that correlate with enhanced catalytic activity. The formation of NiOOH is associated with a reduction in both the total amount of interfacial water and the proportion of 4 H-bonded water. Finally, our investigation into the reversibility of these changes provides insights that could lead to more robust and efficient catalyst designs. Overall, these results illustrate how careful control of material composition and understanding of water’s role can lead to improved performance in electrochemical reactions, opening new avenues for the design of next-generation catalysts.