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- Valdes, A., et al.
(author)
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Solar hydrogen production with semiconductor metal oxides: new directions in experiment and theory
- 2012
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In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 14:1, s. 49-70
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Research review (peer-reviewed)abstract
- An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hematite and TiO(2) functionalized with gold nanoparticles as photoanode materials, and theoretical studies on electro and photo-catalysis of water on a range of metal oxide semiconductor materials, including recently developed implementation of self-interaction corrected energy functionals.
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| 5. |
- Vojvodic, A, et al.
(author)
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Zener tunneling between Wannier-Stark levels in GaAs/AlGaAs superlattices
- 2005
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In: Solid State Communications. - : Elsevier BV. - 1879-2766 .- 0038-1098. ; 136:11-12, s. 580-584
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Journal article (peer-reviewed)abstract
- We have performed a detailed calculation of the inter-Wannier-Stark-ladder Zener tunneling probability P(F) in a wide-miniband GaAs/Al0.3Ga0.7As superlattice under a strong electric field F, the terahertz emission spectrum I(F) of which was measured experimentally. By comparing P(F) and I(F), we confirm that the oscillating behavior of I(F) is due to the Zener tunneling between Wannier-Stark levels.
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- Walton, Alex S., et al.
(author)
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Interface Controlled Oxidation States in Layered Cobalt Oxide Nanoislands on Gold
- 2015
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In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 9:3, s. 2445-2453
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Journal article (peer-reviewed)abstract
- Layered cobalt oxides have been shown to be highly active catalysts for the oxygen evolution reaction (OER; half of the catalytic "water splitting" reaction), particularly when promoted with gold. However, the surface chemistry of cobalt oxides and in particular the nature of the synergistic effect of gold contact are only understood on a rudimentary level, which at present prevents further exploration. We have synthesized a model system of flat, layered cobalt oxide nanoislands supported on a single crystal gold (111) substrate. By using a combination of atom-resolved scanning tunneling microscopy, X-ray photoelectron and absorption spectroscopies and density functional theory calculations, we provide a detailed analysis of the relationship between the atomic-scale structure of the nanoislands, Co oxidation states and substrate induced charge transfer effects in response to the synthesis oxygen pressure. We reveal that conversion from CO2+ to Co3+ can occur by a facile incorporation of oxygen at the interface between the nanoisland and gold, changing the islands from a Co-O bilayer to an O-Co-O trilayer. The O-Co-O trilayer islands have the structure of a single layer of beta-CoOOH, proposed to be the active phase for the OER, making this system a valuable model in understanding of the active sites for OER. The Co oxides adopt related island morphologies without significant structural reorganization, and our results directly demonstrate that nanosized Co oxide islands have a much higher structural flexibility than could be predicted from bulk properties. Furthermore, it is clear that the gold/nanoparticle interface has a profound effect on the structure of the nanoislands, suggesting a possible promotion mechanism.
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