Kohei Sawada (Graduate School of Integrated Frontier Sciences)’s paper has been accepted for Applied Catalysis A: General.
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Authors
Kohei Sawada, Sun Kim, Motonori Watanabe, Jun Tae Song, Miki Inada and
Tatsumi Ishihara
Affiliation
Graduate School of Integrated Frontier Sciences, Department of Automotive Science
Manuscript Title
Magnesium-doped InGaO3 prepared by solid-state reaction for photocatalytic water splitting
Abstract
Effects of cation-doping to InGaO3 on photocatalytic water splitting activity were studied using a solid-state reaction. Among various dopants, it was found that Mg2+ which is a lower-valence cation was effective in significantly increased the photocatalytic water splitting activity. NiO-loaded InGa0.95(Mg)0.05O3 exhibited the highest hydrogen and oxygen evolution rates, 760 and 342 µmol g-1 h-1, respectively. Notably, Brunauer–Emmett–Teller (BET) surface area and bandgap estimated by UV-visible diffuse reflectance (UV-vis DR) spectra were not significantly changed between InGaO3 and InGa0.95(Mg)0.05O3. Photoluminescence (PL) and PL decay spectra confirmed that 5 at% Mg doping effectively suppressed the charge recombination, indicating improved carrier separation. X-ray photoelectron spectroscopy (XPS) revealed the formation of oxygen vacancy, which compensated the charge neutrality and reduced the free electron concentration. Ultraviolet photoelectron spectroscopy (UPS) confirmed that Mg doping lowered the valence band edge of InGaO3 and effectively expanded the driving force for the oxygen evolution reaction, although the conduction band was almost unchanged.
Journal name
Applied Catalysis A: General
Relevant SDGs
SDGs 7 (Affordable and clean energy), SDGs 13 (Climate action)
Comments
This study reports on the photocatalytic properties of indium gallium oxide (InGaO₃) with cation doping. Gallium–indium-based semiconductors have recently attracted attention as highly efficient photocatalysts for water splitting due to their high mobility of photoexcited carriers. However, the mechanism of their high photocatalytic water splitting activity remains insufficient, and only a few research groups have successfully reproduced such performance, which has been a major challenge. We demonstrated that Magnesium doped InGaO₃ , which is a small amount of magnesium—an element with an ionic radius similar to gallium and a lower valence, exhibits high photocatalytic water splitting activity. This enhancement is attributed to the controlled free electron concentration within the catalyst. We aim to utilize these findings as design guidelines to develop even more practical photocatalysts for water splitting.
