Here,
we have demonstrated the synthesis and characterization of
hexacyanoferrate-complex-derived NiFe2O4/CoFe2O4 heterostructures (Ni/Co-HSs) blended with 10%
multiwalled carbon nanotubes (MWCNTs) (C-Ni/Co-HS) as a composite
for the first time to explore its performance in the electrocatalytic
oxygen evolution reaction (OER). First, the structural and morphological
analyses of the as-synthesized composite have been carried out using
X-ray diffraction (XRD) patterns, Fourier-transform infrared (FT-IR)
spectral studies, field emission-scanning electron microscopy (FE-SEM)
with energy dispersive X-ray (EDAX), high-resolution transmission
electron microscope (HR-TEM), X-ray photoelectron spectroscopy (XPS),
and Brunauer–Emmett–Teller (BET) analyses. Second, C-Ni/Co-HS
loaded at a 316 stainless steel (SSL) mesh electrode was studied as
an efficient and stable electrocatalyst, which firmly initiated the
OER at a low potential of 1.47 V (vs reversible hydrogen electrode
(RHE)) compared to the benchmark catalyst such as RuO2 or
other counterparts, ferrite-loaded electrodes such as iron oxide (Fe2O3), nickel ferrite (NiFe2O4), cobalt ferrite (CoFe2O4), etc. Accordingly,
a very low overpotential of 240 mV was observed for OER at a current
density of 10 mA cm–2 under alkaline 1.0 M KOH conditions
where the Tafel slope was calculated as 42 mV dec–1 at the C-Ni/Co-HS-loaded 316 SSL mesh electrode when compared to
the counterpart, NiFe2O4/CoFe2O4 heterostructure (Ni/Co-HS)-loaded electrode, i.e., in the
absence of 10% MWCNTs under identical electrochemical conditions.
Besides, an excellent faradic efficiency was measured for C-Ni/Co-HS,
propounding that the carbon support has minimized the corrosion and
the additional oxidation of the active electrocatalyst during the
course of the electrocatalytic OER test. The stability of the active
C-Ni/Co-HS composites was studied under continued oxygen evolution
for several hours at an applied potential of 1.67 V (vs RHE) to interpret
the heterostructure phenomenal long-term stability and higher electrocatalytic
activity toward OER. Thus, the developed inorganic-complex-derived
heterostructure-based electrocatalyst provides an alternative to noble
metal systems to afford a simple, highly efficient, and stable process
for OER.
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