Ti-Based
Precursor Synthesized from Ball Milling as
a Starting Material to Design an Active and Stable Ti2O3@NixFeyTiz Nanoheterostructure for the Oxygen
Evolution Reaction in an Alkaline Medium
Ball
milling, an eco-friendly material synthesis route, was used
to produce a Ti-based precursor from a mixture of metallic Ti and
TiO2 powders to obtain a corrosion-resistant and conductive
support for the oxygen evolution reaction in an alkaline medium. The
obtained materials were subsequently impregnated with Ni and Fe salts
before being thermally treated under hydrogen. Thanks to this synthesis
route, composite materials consisting of a Ni- and Fe-containing active
phase deposited onto a TiyOx substrate were obtained. The chemical nature of
phases composing this precursor material directly depends on the Ti/TiO2 mass ratio. For a mass ratio of 50%, the Ti-based precursor
(sample labeled Ti50), initially composed of TiO2 and Ti hydride phases, is transformed, after impregnation with Fe
and Ni salts and heat treatment under H2, into a highly
electron conductive Ti2O3 phase, leading to
a high oxygen evolution reaction (OER) activity. The influence of
active phase loading and the Ni/Fe atomic ratio on the OER activity
was subsequently investigated by performing electrochemical experiments.
Different physicochemical techniques (X-ray diffraction (XRD), transmission
electron microscopy (TEM), and inductively coupled plasma-optical
emission spectrometry (ICP-OES)) were performed to characterize the
composition, structure, and morphology of the different composite
catalysts in order to evidence a correlation between materials’
properties and their electroactivity toward OER. The sample labeled
30 atom % NiFe (50–50)-Ti50 sample (i.e, Ni/Fe isoatomic
ratio and atomic percent of the Ni- and Fe-containing active phase
of 30%) appears as the most efficient material, since an overpotential
of only 310 mV is required to drive a current density of 10 mA cm–2. A chronopotentiometry test was carried out to ensure
the stability of electrochemical performances after a long-term use
of 7 days. Finally, post-mortem Raman spectroscopy and TEM measurements
were performed to inquire into surface restructuring phenomena affecting
the nanoheterostructured catalyst under working conditions.