“Dark” Photocatalysis: The Degradation of Organic Molecules Anchored to Dark Microdomains of Titanium Dioxide

Haick, Hossam; Paz, Yaron

doi:10.1002/cphc.200200622

Cited by 43 publications

(35 citation statements)

References 33 publications

(22 reference statements)

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“…An interesting indication that direct hole-mediated oxidation is not the only oxidation pathway in TiO 2 photocatalysis is found in observations of 'remote' oxidation [38,286,701,727,[740][741][742][743][744][745][746][747][748][749][750][751]. In this phenomenon, oxidation events occur at regions of a TiO 2 sample not exposed to light or at non-TiO 2 surfaces that are lineof-sight from irradiated TiO 2 surfaces.…”

Section: Direct Versus Indirect Eventsmentioning

confidence: 96%

A surface science perspective on TiO2 photocatalysis

Henderson

2011

Surface Science Reports

1,861

1,634

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a b s t r a c tThe field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO 2 photocatalysis. This review highlights, from a surface science perspective, recent literature that provides molecular-level insights into photon-initiated events occurring at TiO 2 surfaces. Seven key scientific issues are identified in the organization of this review. These are: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form. This review ends with a brief examination of several chemical processes (such as water splitting) in which TiO 2 photocatalysis has made significant contributions in the literature.

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Section: Direct Versus Indirect Eventsmentioning

confidence: 96%

A surface science perspective on TiO2 photocatalysis

Henderson

2011

Surface Science Reports

1,861

1,634

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“…The lack of surface diffusion is reasonable, as quantum chemical calculations have reported large energy barriers to diffusion of O-adatoms on TiO 2 [53]. Although diffusion of oxidizing species has been reported to cause "remote photocatalysis" on TiO 2 S this phenomenon occurs very slowly, requiring hours to fully mineralize species at a distance of more than 10 mm from photocatalytic sites [54,55]. SI-SECM proceeds too rapidly for this to be significant, as will be discussed in section 4.2.…”

Section: Numerical Simulationmentioning

confidence: 97%

Redox Titrations via Surface Interrogation Scanning Electrochemical Microscopy at an Extended Semiconducting Surface for the Quantification of Photogenerated Adsorbed Intermediates

Simpson

Rodríguez‐López

2015

Electrochimica Acta

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“…36 We therefore tentatively attribute the lack of a first order reaction order on TiO2 to a higher mobility of surface holes, where previous studies have shown that surface holes (or their oxidized equivalent) on TiO2 are highly mobile and can migrate for several microns before reacting. 56 …”

Section: Possible Water Oxidation Mechanisms On Titaniamentioning

confidence: 99%

Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO₂ Photoanode: A Rate Law Analysis

et al. 2017

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ABSTRACT. It has been more than 40 years since Fujishima and Honda demonstrated water splitting using TiO2, yet there is still no clear mechanism by which surface holes on TiO2 oxidize water. In this article, we use a range of complementary techniques to study this reaction that provide a unique insight into the reaction mechanism. Using transient photocurrent (TPC) and 2 transient absorption spectroscopy (TAS), we measure both the kinetics of electron extraction (t50% ~200 µs, 1.5 VRHE) and the kinetics of hole oxidation of water (t50% ~100 ms, 1.5 VRHE) as a function of applied potential, demonstrating the water oxidation by TiO2 holes is the kinetic bottleneck in this water splitting system. Photo-induced absorption spectroscopy (PIAS) measurements under 5 s LED irradiation are used to monitor the accumulation of surface TiO2 holes under conditions of photo-electrochemical water oxidation. Under these conditions we find that the surface density of these holes increases non-linearly with photocurrent density. In alkali (pH 13.6), this corresponded to a rate law for water oxidation that is 3 rd order with respect to surface hole density, with a rate constant = 22 ± 2 nm 4 .s -1 . Under neutral (pH = 6.7) and acidic (pH = 0.6) conditions the rate law was 2 nd order with respect to surface hole density, indicative of a change in reaction mechanism. Although a change in reaction order was observed, the rate of reaction did not change significantly over the wide pH range examined (with TOFs per surface hole in the region of 20 -25 s -1 at ~1 sun irradiance). This showed that the rate limiting step does not involve OH -nucleophilic attack and demonstrated the versatility of TiO2 as an active water oxidation photocatalyst over a wide range of pH.TOC graphic

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“Dark” Photocatalysis: The Degradation of Organic Molecules Anchored to Dark Microdomains of Titanium Dioxide

Cited by 43 publications

References 33 publications

A surface science perspective on TiO2 photocatalysis

A surface science perspective on TiO2 photocatalysis

Redox Titrations via Surface Interrogation Scanning Electrochemical Microscopy at an Extended Semiconducting Surface for the Quantification of Photogenerated Adsorbed Intermediates

Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO₂ Photoanode: A Rate Law Analysis

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“Dark” Photocatalysis: The Degradation of Organic Molecules Anchored to Dark Microdomains of Titanium Dioxide

Cited by 43 publications

References 33 publications

A surface science perspective on TiO2 photocatalysis

A surface science perspective on TiO2 photocatalysis

Redox Titrations via Surface Interrogation Scanning Electrochemical Microscopy at an Extended Semiconducting Surface for the Quantification of Photogenerated Adsorbed Intermediates

Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO2 Photoanode: A Rate Law Analysis

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Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO₂ Photoanode: A Rate Law Analysis