Heterogeneous photocatalytic decomposition of saturated carboxylic acids on titanium dioxide powder. Decarboxylative route to alkanes

Kraeutler, Bernhard; Bard, Allen J.

doi:10.1021/ja00487a001

Cited by 523 publications

(246 citation statements)

References 3 publications

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“…The presence of acetate hampers the photodegradation process, in agreement with literature data that report the chance of the acetate substrate to behave as a hole scavenger effect via the so-called photo-Kolbe reaction. 12 The effect is similar to the case of methanol, although the concentration of the alcohol was about an order of magnitude higher.…”

Section: Resultsmentioning

confidence: 64%

“…The same source lists a number of common effective hole scavengers. The more commonly used are: methanol and ethanol, 14,20 2-propanol, 20 but also acetic acid, 14,12 salicylic acid and EDTA. 14 The goal of the work accounted in the present article was to show the influence, in the photocatalytic digestion, of species possibly present in solution and capable to trap and consume electrons or positive holes and, thus, to interfere favourably or unfavourably in the oxidation mechanism of organic substrates.…”

Section: Introductionmentioning

confidence: 99%

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Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Cavicchioli

Gutz

2002

J. Braz. Chem. Soc.

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A influência de scavengers de elétrons e de lacunas positivas na digestão fotocatalítica de matéria orgânica na presença de partículas de TiO 2 em suspensão, foi investigada. O processo, que visa a determinação eletroquímica de traços de metais pesados em amostras de água, foi acompanhado mediante observação da recuperação da onda voltamétrica de Cd(II) em presença de EDTA, escolhido como ligante-modelo na simulação do efeito complexante da matéria orgânica natural. Confirmouse o poder acelerador de O 2 , que atua como removedor de elétrons. Na ausência de O 2 , função análoga é exercida pelo íon nitrato, mas não, ao menos aparentemente, pelo analito Cd(II). Já a adição de CH 3 OH apresenta efeito antagônico de scavenger de lacunas positivas, o que pode explicar porque a operação na presença de acetato (usado como tampão de pH), ao mesmo tempo em que proporciona um eficaz controle da acidez do meio, provoca uma certa redução do rendimento da fotodegradação.The influence of electron and hole scavengers in the photocatalytic digestion of organic matter in the presence of suspended particles of TiO 2 was investigated. The process, aiming at the electrochemical determination of traces of heavy metals in water samples, was followed through the recovery of the voltammetric wave of Cd(II) in the presence of EDTA, chosen as model ligand that mimics the complexing effect of natural dissolved organic matter. The accelerating power of O 2 , acting as electron scavenger, was confirmed. In the absence of O 2 , a similar function is played by nitrate ions but not, as it seems, by the analyte, Cd(II). On the other hand, CH 3 OH exhibits an antagonist effect as hole scavenger. This observation may explain why the acetate (from the pH buffer), used to control the medium acidity, leads to a certain reduction in the photocatalytic yield.

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Section: Resultsmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Cavicchioli

Gutz

2002

J. Braz. Chem. Soc.

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“…[8][9][10][11][12][13] In order to modify TiO 2 surfaces with noble metal nanoparticles, several methods are commonly used such as photoassisted deposition, impregnation, and physical mixing. [14][15][16][17] In the present work, we demonstrate that a very facile and straightforward Pt self-decoration of TiO 2 nanotube walls can be achieved in situ, that is during tube growth, by using Ti-Pt alloys with a small amount of Pt (in our case 0.2 at%) for the anodization process. We find that such self-decorated noble metals on TiO 2 nanotubes provide a drastic improvement of the photocatalytic hydrogen evolution under UV as well as under visible light conditions.…”

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confidence: 91%

Self-decoration of Pt metal particles on TiO₂ nanotubes used for highly efficient photocatalytic H₂ production

et al. 2014

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Pt decorated TiO 2 has, over the past decades, been a key material for photocatalytic hydrogen production. The present work shows that growing anodic self-organized TiO 2 nanotubes from Ti-Pt alloy with a low Pt content of 0.2 at% leads to oxide nanotube layers that are self-decorated with Pt nanoparticles of 4-5 nm in diameter. The average particle spacing is in the range of~50 nm and is partially adjustable by the anodization conditions. This intrinsic decoration of TiO 2 nanotubes with Pt leads to a highly active photocatalyst for the production of H 2 under UV or visible light conditions.Since Fujishima and Honda in 1972 showed the feasibility to produce hydrogen, the fuel of the future, by photoelectrochemical water splitting using a TiO 2 electrode, vast efforts have been dedicated to optimize systems to enhance the hydrogen yield. 1 The principle of this pathway to hydrogen is based on using a semiconductor for light absorption and formation of excited electron-hole pairs that then on the semiconductor surface react with an environmental H-source. A key requirement of the semiconductor is that it has suitable band-edge positions to allow generation of H 2 (namely a conduction band edge with a negative potential to the H 2 /H + redox potential). If the goal is to achieve a photocatalytic hydrogen production system that operates without external bias (i.e., under open circuit conditions), then also the transfer of holes from the valence band to the environment should be not only thermodynamically possible but also kinetically fast. 2,3 In the case of TiO 2 , most measures to enhance the kinetics are the use of sacrificial agents such as methanol, ethanol and decorating the surface with suitable charge transfer co-catalysts.Other key parameters for an effective hydrogen evolution from TiO 2 are a large surface area and an optimized geometry of the photocatalyst. For the latter reason, one-dimensional nanostructures have attracted wide interest in this field, as they provide a high aspect ratio with an optimized light absorption path and an orthogonal carrier separation. A most straightforward approach towards directional structures is self-organized TiO 2 nanotube arrays. To produce these nanotube structures a Ti metal substrate can be anodized under self-organizing electrochemical conditions. 4 The advantage of an anodic formation is not only simplicity of the process but also the easiness of geometry control (length, diameter, wall thickness) via the selection of suitable anodization parameters. 4 In the context of H 2 production from TiO 2 , as co-catalysts most active are noble metal nanoparticles (mainly Pt) that act very efficiently on TiO 2 nanostructures -in fact in order to obtain measurable contents of H 2 from TiO 2 under non-biased conditions (without the use of a counter electrode and by applying a potential difference) co-catalyst decoration is mandatory. [5][6][7] There are mainly two beneficial effects ascribed to Pt decoration: (i) changes in surface band bending in TiO 2 induced by the meta...

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“…The similar process is known for the TiO2 photocatalyst, known as the photo-Kolbe reaction, where alkyl radicals are generated from various carboxylic acids. 24 In this study, we demonstrated how the photocatalytic microreactors can be utilized for the study for organic reactions, and clarified their feature. As a demonstration, we studied the reactions of carboxylic acids and the reactivity of the alkyl radicals generated from the carboxylic acids, in analogy with the reactions utilizing photosensitizers.…”

Section: Introductionmentioning

confidence: 82%

Study on Photocatalytic Organic Reactions Using Photocatalytic Microreactors

et al. 2014

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Photocatalytic organic reactions were performed using automatic photocatalytic microreactor, where several open-end capillaries with photocatalytic materials coated inside were just soaked in a test tube including a reactant solution. Organic reactions of the alkyl radicals generated from carboxylic acids due to the photo-Kolbe reaction was studied, in analogy with the reactions using a photosensitizer. This methodology features the reusability of the reactor and an easy process for analysis due to easy separation of the reactant solution.Keywords Photocatalytic reaction, microreactor, decarboxylation

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Heterogeneous photocatalytic decomposition of saturated carboxylic acids on titanium dioxide powder. Decarboxylative route to alkanes

Cited by 523 publications

References 3 publications

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Self-decoration of Pt metal particles on TiO₂ nanotubes used for highly efficient photocatalytic H₂ production

Study on Photocatalytic Organic Reactions Using Photocatalytic Microreactors

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Heterogeneous photocatalytic decomposition of saturated carboxylic acids on titanium dioxide powder. Decarboxylative route to alkanes

Cited by 523 publications

References 3 publications

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Self-decoration of Pt metal particles on TiO2 nanotubes used for highly efficient photocatalytic H2 production

Study on Photocatalytic Organic Reactions Using Photocatalytic Microreactors

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Self-decoration of Pt metal particles on TiO₂ nanotubes used for highly efficient photocatalytic H₂ production