A Co and Fe bimetallic MOF with enhanced electrocatalytic oxygen evolution performance: exploring the electronic environment modifications upon Fe incorporation

Abstract

The incorporation of iron into the cobalt-based metal–organic framework (Co-MOF) modifies the electronic environment and the resulting bimetallic MOF exhibits enhanced oxygen evolution reaction (OER) performance. The Co-MOF, Fe-MOF, and different ratios of bimetallic Co–Fe-MOFs are prepared using 2,2′-bipyridine 4,4′-dicarboxylic acid (H₂bpdc) by a single-step hydrothermal process. The MOFs are evaluated by necessary spectroscopy and microscopy techniques like Fourier transform infrared spectroscopy, inductively coupled plasma emission spectroscopy, powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The incorporation of Fe³⁺ into the Co-MOF significantly increases the electrocatalytic activity of the resulting bimetallic Co–Fe-MOF towards the OER. An optimized bimetallic MOF having a Co : Fe ratio of 2 : 1 shows the lowest overpotential (310 mV) to realize the 10 mA cm⁻² current density and the lowest Tafel slope of 53 mV dec⁻¹ with excellent durability in comparison to the Co-MOF, the Fe-MOF, and the state-of-the-art catalyst, RuO₂. Furthermore, this manuscript addresses the inherent electrocatalytic properties of MOF-based electrocatalysts and demonstrates their possible exploitation in water electrolysis.