Specific roles of Fe in NiFe-MOF nanosheet arrays on oxygen evolution reaction kinetics in alkaline media

Although great progress has been made in the study of the performance of NiFe-based electrocatalysts, the specific role of Fe is still under debate, largely due to the lack of desirable platforms. Metal-organic frameworks (MOFs) with uniform pore size, large specific surface area and uniform distribution of active sites are ideal platforms. Therefore, we synthesized a series of NiM-MOF (M = Fe, Co, Mn, Cu, or Zn) nanosheet arrays by solvothermal method with MOF as a platform and systematically investigated their OER properties. XRD and XPS characterizations show that the introduction of Fe into Ni-MOF not only leads to lower crystallinity, but also increases the oxidation state of Fe and modifies the electronic structure of Ni sites. This is further confirmed by DFT calculations, where the d-band center is closer to the Fermi level, enhancing the ability to adsorb/desorb oxygen-containing intermediates and thereby improving the intrinsic activity of NiFe-MOF.