Abstract
Thin film of indium iron oxide, InFeO3, with a two-dimensional natural superlattice structure was proposed as one of the candidate photoelectrodes for visible- and ultraviolet-light-driven water splitting. A first principle calculation shows that InFeO3 is a charge transfer-type insulator with a bandgap energy (Eg) of 2.5 eV. Flat band potentials are calculated from Mulliken electronegativities, and they show an appropriately placed conduction band to enable H2 evolution. Despite its wide Eg, the photocurrent of InFeO3 in the visible region is comparable to that of α-Fe2O3 (Eg = 2.1 eV), a conventional oxide photoelectrode, possibly owing to its intrinsic structural anisotropy, reducing recombination losses of photogenerated electron–hole pairs. Furthermore, InFeO3 shows enhanced light absorption and photocurrent in the ultraviolet region compared with α-Fe2O3. The onset potential of photocurrent of InFeO3 is significantly lower than that of α-Fe2O3. These properties suggest that InFeO3 is a promising candidate for water splitting by visible and ultraviolet light.
Highlights
Photoelectrochemical (PEC) water splitting has been studied extensively as a promising technique to produce clean and sustainable hydrogen fuel
We have focused on the InFeO3-based photoelectrode, and its PEC properties are investigated in comparison with those of α-Fe2O3
Scitation.org/journal/apm edge states consist of the O 2p or Fe 3d orbitals, and the In 5s state is located at 5.0 eV, which is significantly far from the conduction band minimum (CBM)
Summary
Photoelectrochemical (PEC) water splitting has been studied extensively as a promising technique to produce clean and sustainable hydrogen fuel. IFO films were deposited on the substrate at 700 ○C under the oxygen pressure of 0.1 Pa. The as-grown scitation.org/journal/apm and c = 12.2 Å, which are close to those reported for bulk IFO.10 In the XRD pattern of the α-Fe2O3 film grown on TTO, the only (110) and (220) peaks of the corundum crystalline structure [see Fig. 1(b)] are observed, indicating that the α-Fe2O3 film is a single crystal with an orientation along [110].
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