Ultrathin Trimetal-Organic Framework Nanosheet Electrocatalysts for the Highly Efficient Oxygen Evolution Reaction

Synthesis of ultrathin metal-organic framework (MOF) nanosheets for highly efficient oxygen evolution reaction (OER) is prevalent, but still many challenges remain. Herein, a facile and efficient three-layer method is reported for the synthesis of NiCoFe-based trimetallic MOF nanosheets, which can be directly used for the oxygen evolution reaction in alkaline conditions. The physical characterization and morphology of trimetallic MOF nanosheets were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). By optimizing the molar ratio of Ni/Co/Fe atoms, a series of MOFs with different metal proportions were synthesized. Among them, the as-prepared (Ni₃Co₁)₃Fe₁-MOF nanosheets can deliver a current density of 10 mA cm^-2 at a low overpotential of 245 mV with a small Tafel slope of 50.9 mV dec^-1 in an alkaline electrolyte and exhibit excellent stability. More importantly, through the characterization of the intermediates in the OER process, the possible source of the catalytic active species is the electrochemically transformed metal hydroxides and oxyhydroxides.