Effect of the valence state of initial iron source on oxygen evolution activity of Fe-doped Ni-MOF

The coordination structure of MOF is strongly influenced by central metal ions. Here, we designed and prepared iron-doped nickel metal-organic framework (Fe-doped Ni-MOF) by employing different initial iron sources (Fe2+, Fe3+). Specifically, Fe-doped Ni-MOF with divalent iron ions as initial iron sources exhibits superior performance with respect to trivalent iron ions, showing excellent electrocatalytic performance toward OER with an overpotential (294 mV at 10 mA cm(-2)), low Tafel slope (47.45 mV dec(-1)) and large electrochemically active surface area in alkaline electrolytes. Furthermore, there is no obvious decay after long-term operation up to 25 h. To inspect the origin of OER activity enhancement, we resorted to XRD, SEM, TEM, XPS and N-2 adsorption-desorption techniques and various electrochemical methods to analyze them in detail. These studies provide a new vision into understanding Fe-doped Ni-MOF for OER, shedding light on designing novel and highly efficient MOF materials for electrocatalysis. [GRAPHICS] .