We carried out the liquid phase-atomic layer deposition (LP-ALD) of α-Fe2O3. The deposition temperature (95 °C) and rate (6.3 nm min−1) are much lower and higher than those offered by cutting edge gas-phase ALD techniques, respectively.
The use of nanoscale heterostructures
is an effective approach
for developing catalysts that are free of precious metals for sustainable
energy conversion. In this study, a sequenced successive ionic layer
adsorption and reaction (sequenced-SILAR) method was developed for
the fabrication of Ni(OH)2/FeOOH heterostructures. In this
method, the order of the deposition cycles of individual Ni(OH)2 and FeOOH layers was programmed to control the thickness
and stacking order of these layers in the heterostructure. The sequenced-SILAR
process using an Fe2+ solution as the iron source produced
dense heterojunctions offering overpotentials of 330 and 234 mV at
10 mA cm–2 for an oxygen evolution reaction (OER)
on a flat, conducting oxide substrate and porous Ni foam, respectively.
Investigation of the deposition-sequence-dependent OER activity indicated
that the Ni(OH)2/FeOOH coupling effects may extend to the
Ni2+ active sites located about 10 nm from the heterointerface.
When an Fe3+ precursor was employed in the sequenced-SILAR
process, dense heterojunctions were not produced because of the formation
of isolated FeOOH particles. As a result, an excellent overpotential
was not obtained. In principle, the sequenced-SILAR method can be
extended to the fabrication of various types of heterostructures.
However, the deposition conditions must be carefully designed to offer
strong interfacial coupling effects.
This paper describes a simple, low-temperature, and environmentally friendly aqueous route for the layer-by-layer nanometric growth of crystalline α-Fe2O3. The formation mechanism involves alternative sequences of the electrostatic adsorption of...
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