Photo-oxidation reaction of water on an n-TiO2 electrode. Improvement in efficiency through formation of surface micropores by photo-etching in H2SO4

Nakato, Yoshihiro; Akanuma, Hideyuki; Shimizu, Junichi; Magari, Yoshifumi

doi:10.1016/0022-0728(95)04007-b

Cited by 62 publications

(48 citation statements)

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“…In this context, it is to be noted that the onset potential of the photocurrent (U on ) in acidic solutions (in the absence of alcohols) is largely (about 0.5 V) more positive than the flat-band potential (U^ (Figure 1), whereas the U on in neutral and alkaline solutions lies much closer to (12,14,18). The latter fact is explained by taking account of the formation of easily oxidized surface species such as Ti-O" in the neutral and alkaline solutions, followed by their oxidation by the holes.…”

Section: Discussionmentioning

confidence: 95%

Photooxidation Reaction of Water on an n-TiO₂ Electrode

Magari

Ochi

Yae

et al. 1997

ACS Symposium Series

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The mechanism of the photooxidation reaction of water on an n-TiO 2 (rutile) electrode in acidic electrolyte has been studied by in situ photoluminescence as well as photocurrent measurements. Addition of alcohols to the electrolyte caused an appearance of a shoulder in the photocurent-potential curve and an increase in the illumination intensity limited photocurrent, together with a decrease in the photoluminescence intensity. Detailed analyses of the results have given strong support to our previously proposed new mechanism that surface Ti-OH group is not oxidized by photogenerated holes but that Ti-OH group or OH -ion present in bulk defects near the electrode surface is oxidized, and thus the photooxidation reaction of water on n-TiO 2 (rutile) in acidic solutions proceeds mainly through the oxidation of such bulk species by the holes.The electrolysis of water into hydrogen and oxygen is an important reaction in energy conversion technologies. Though hydrogen evolution proceeds efficiently on some metal electrodes, oxygen evolution has a fairly high overvoltage, resulting in a significant loss in the energy conversion efficiency (7). For finding efficient electrode materials for the oxygen evolution, it seems inevitably necessary to clarify its reaction mechanism in detail on a molecular level.The oxygen evolution reaction occurs at large positive potentials where most metal electrodes are covered with thin (or rather thick) native oxide layers. This implies that studies of the reaction mechanism on metal oxide electrodes are very important. In this respect, the photooxidation reaction of water on an n-Ti0 2 electrode (2) is very interesting. A number of studies have been made on the mechanism of this reaction (5-77), but the details still remain unclear because the water oxidation is a four-electron process and will proceed via many reaction intermediates at the electrode surface.We found previously that the n-Ti0 2 (rutile) electrode showed a photolumi nescence (PL) band peaked at 840 nm which could be explained as arising from a surface reaction intermediate or a species closely related to it (72). This enabled us to use in situ 1

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Section: Discussionmentioning

confidence: 95%

Photooxidation Reaction of Water on an n-TiO₂ Electrode

Magari

Ochi

Yae

et al. 1997

ACS Symposium Series

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“…Im Rahmen von anodischen Verfahren wurde auch über die Herstellung von photoelektrochemischen ¾tzkanä-len [56][57][58] und von weniger organisierten (üblicherweise nicht auf dem Substrat haftenden) TiO 2 -Nanoröhrenbündeln [73] berichtet. Später wurde dieses Verfahren als RBA-Anodisierung (rapid breakdown anodization, RBA) bezeichnet [74] und auf andere Elektrolyte [73][74][75] und Metalle [74,76] bzw.…”

Section: Elektrochemische Synthese; Vergleich Mit Anderen Ansätzenunclassified

TiO₂‐Nanoröhren: Synthese und Anwendungen

2011

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TiO2 ist eine der am besten untersuchten Verbindungen in den Materialwissenschaften und weist einige herausragende Eigenschaften auf, die z. B. für die Photokatalyse, für farbstoffsensibilisierte Solarzellen oder für biomedizinische Funktionseinheiten genutzt werden. 1999 zeigten erste Berichte, dass es möglich ist, hoch geordnete Anordnungen von TiO2‐Nanoröhren durch eine einfache, aber optimierte elektrochemische Anodisierung einer Ti‐Metallfolie herzustellen. Dies löste intensive Forschungsaktivitäten aus, deren Schwerpunkt auf der Herstellung und der Modifizierung sowie auf den Eigenschaften und Anwendungen dieser eindimensionalen Nanostrukturen lagen. Dieser Aufsatz geht auf all diese Aspekte und die zugrundeliegenden Prinzipien und funktionellen Haupteigenschaften von TiO2 ein und will außerdem versuchen, Entwicklungsperspektiven für das Gebiet aufzuzeigen.

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“…However, the high substrate temperature (873 K) during deposition led to a small surface area for the films. To address this, surface etching processes have been attempted to enlarge the surface area of various materials such as the photoelectrochemical etching of TiO 2 in H 2 SO 4 solution [22,23]. Ohno et al [24,25] have reported that anatase TiO 2 dissolves into a hydrofluoric acid (HF) solution when TiO 2 powder is suspended in an HF solution at room temperature, thus showing that the TiO 2 surface could be easily etched by an HF solution and the etching process can be easily controlled by changing the HF concentrations.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Chemical Etching by HF Solution on the Photocatalytic Activity of Visible Light-responsive TiO2 Thin Films for Solar Water Splitting

Kitano

Iyatani²,

Tsujimaru³

et al. 2008

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The effect of chemical etching by HF solution on the photoelectrochemical performance and photocatalytic activity of visible light-responsive TiO 2 (Vis-TiO 2 ) thin films prepared by a radio-frequency magnetron sputtering method has been investigated. It was found that VisTiO 2 thin films treated with HF solution (HF-Vis-TiO 2 ) exhibit a remarkable enhancement of the photoelectrochemical performance not only under UV but also visible light irradiation as compared to untreated Vis-TiO 2 . The incident photon to current conversion efficiencies reached 66 and 9.4% under UV (k = 360 nm) and visible light (k = 420 nm), respectively. The HF-Vis-TiO 2 thin films have a larger surface area and higher donor density than Vis-TiO 2 , indicating that the remarkable increase in the photocurrent may be due to the short diffusion length of the photoformed holes in reaching the solid-liquid interface as well as to the high conductivity. Moreover, the HF-Vis-TiO 2 thin films were found to act as efficient photocatalysts for the decomposition of water with the separate evolution of H 2 and O 2 from H 2 O under visible or sunlight irradiation.

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Photo-oxidation reaction of water on an n-TiO2 electrode. Improvement in efficiency through formation of surface micropores by photo-etching in H2SO4

Cited by 62 publications

References 10 publications

Photooxidation Reaction of Water on an n-TiO₂ Electrode

Photooxidation Reaction of Water on an n-TiO₂ Electrode

TiO₂‐Nanoröhren: Synthese und Anwendungen

The Effect of Chemical Etching by HF Solution on the Photocatalytic Activity of Visible Light-responsive TiO2 Thin Films for Solar Water Splitting

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Photo-oxidation reaction of water on an n-TiO2 electrode. Improvement in efficiency through formation of surface micropores by photo-etching in H2SO4

Cited by 62 publications

References 10 publications