Hydrogen (H2) is a green fuel, synthesized usually by water electrolysis. However, a large amount of energy is required in this process and electrocatalysts are needed, especially for the half-reaction so-called Oxygen Evolution Reaction (OER), which request a high overpotential to occur. In this context, this work reports new cobalt-doped iron oxides derived from Zeolitic Imidazolate Framework-67 (ZIF-67) as potential electrocatalyst for OER. The materials were obtained via impregnation of Fe2+ ions into ZIF-67 using methanol or ethanol as solvent, follow by calcination at 350°C. Bimetallic oxides were named here Fe/O/Co(M) and Fe/O/Co(E). The electrocatalysts were characterized by XRD, FT-IR and SEM-EDS. The electrochemical properties for OER were investigated using linear sweep voltammetry (LSV) in KOH 1 mol L-1.
Figure 1: Experimental diffraction pattern ((a) and (b)) and (c) LSV data for cobalt-doped iron oxides electrocatalysts. (Attached in the PDF document)
XRD data indicates the formation of two crystalline phases (Fe2O3 + Fe3O4) for the material obtained in ethanol and one phase (Fe2O3) for the sample synthesized in methanol. The presence of cobalt into the iron oxides were confirmed by the shifts in the XRD signals and using EDS spectroscopy. Signals of Fe-O and Co-O vibrational modes were also observed in the FT-IR spectra. SEM images shows irregular morphologies for both materials. The electrocatalytic activity for the OER was evaluated in alkaline medium and both materials show overpotential of 273 to produce a current density of 10 mA cm-2. These results are similar or superior to those ones reported in the literature.