Fe–Co–Ni trimetallic organic framework chrysanthemum-like nanoflowers: efficient and durable oxygen evolution electrocatalysts

Abstract

By mixing Fe, Co, and Ni metal species (FCN) in equimolar ratios, multivariate metal–organic frameworks (MOFs) with unique chrysanthemum nanoflower structures were successfully fabricated on nickel foam (NF) via a facile one-step solvothermal method. We observed that the structure and oxidation power of Ni in the FCN-BTC MOF exhibited a strong correlation with the OER activity; this indicates that the OER activity originates from its special structure and the Ni active site. Next, the catalysts with nanosheets were assembled into chrysanthemum nanoflower structures and doped with Co, which led to an increase in the contact area between the electrode material and the electrolyte. This provided a good environment for ion and electron transport. Finally, the addition of Fe allowed the FCN-BTC MOF catalyst to have a stronger active site. Notably, in 1 M KOH solution, this catalyst only requires overpotentials of 218, 250, and 268 mV to achieve current densities of 10, 100, and 300 mA cm⁻², respectively, with a Tafel slope of only 29.3 mV dec⁻¹. Furthermore, a current density loss of only 3.5% was observed at 50 mA cm⁻² after 24 h of continuous operation. This new trimetallic MOF electrocatalyst exhibits excellent OER performance and provides a new method for the rational development of high efficiency electrocatalysts.