Bimetal-MOF nanosheets as efficient bifunctional electrocatalysts for oxygen evolution and nitrogen reduction reaction

Metal-organic frameworks (MOFs) have emerged as promising electrocatalysts due to their controllability and diversity in functional species of metal centers and organic linkers. Herein, two-dimensional (2D) bimetal-MOFs (Co_xFe-MOF) nanosheets with a thickness of ∼10 nm are synthesized and employed for OER and NRR in alkaline medium. By regulating the composition of Co_xFe-MOF, the optimized Co₃Fe-MOF can achieve an overpotential of 280 mV at a current density of 10 mA cm^-2 with a small Tafel slope of 38 mV dec^-1 in 1.0 M KOH electrolyte, outperforming the commercial RuO₂ (351 mV at 10 mA cm^-2, 99 mV dec^-1). The enhanced OER performance can be attributed to the abundant active centers and the positive coupling effect between Co and Fe metal ions in the MOF. Additionally, the NRR performance of the obtained Co₃Fe-MOF is evaluated on glassy carbon electrode to achieve real NH₃ faradaic efficiencies (FE) and NH₃ yield rates. The Co₃Fe-MOF delivers a FE up to 25.64% with the corresponding NH₃ yield rate of 8.79 μg h^-1 mg_cat^-1 at -0.2 V versus the reversible hydrogen electrode (vs. RHE) in 0.1 M KOH electrolyte. The results indicate the potential application of 2D MOFs in NRR and provide the rational design of efficient electrocatalysts for coupling both OER and NRR in a full-cell configuration.