Light-intensity dependence in photocatalytic decomposition of water over K4Nb6O17 catalyst

Tabata, Soichi; Ohnishi, H.; Yagasaki, Eriko; Ippommatsu, Masamichi; Domen, Kazunari

doi:10.1007/bf00806072

Cited by 34 publications

(32 citation statements)

References 13 publications

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“…Inherently, this conclusion is common for both WS and photocatalytic oxidation of contaminants. Indeed, such dependence on the light intensity was found both for OWS11, 12 and for PDP 13. 14 Measuring of the above‐described intensity dependence is straightforward for oxidative photocatalytic reactions because these reactions are initiated by one OH .…”

Section: Carrier Generation and Bulk Recombinationmentioning

confidence: 90%

Effect of Bed Height on the Performance of a Fixed Mo/HZSM‐5 Bed in Direct Aromatization of Methane

Song

Liu

et al. 2016

Chem Eng & Technol

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The catalyst‐overloading strategy is often employed to extend the catalytic lifetime of fixed catalyst bed reactors in chemical processes. The applicability of this strategy to the Mo/HZSM‐5 catalyst for non‐oxidative methane dehydroaromatization was confirmed for the first time by examining the influence of bed height on the catalytic stability and lifetime aromatic productivity of an integral fixed Mo/HZSM‐5 bed at a defined temperature and different CH4 superficial velocities. Increasing the bed height proved to have a very limited effect on extending either the stable period of aromatics production of the bed or its lifetime aromatics productivity. Simultaneous coke formation over all layers of the bed was also confirmed to be responsible for rapid deactivation of the whole bed, and pyrolysis of the intermediate C2H4 was found to be the dominant route to coke formation.

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Section: Carrier Generation and Bulk Recombinationmentioning

confidence: 90%

Effect of Bed Height on the Performance of a Fixed Mo/HZSM‐5 Bed in Direct Aromatization of Methane

Song

Liu

et al. 2016

Chem Eng & Technol

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“…Possibly, an even higher initial reaction rate can be achieved at higher intensity (limited here by the experimental setup). However, it is likely that the observed dependence will change at even higher light intensities towards a response equal to the square root of the light intensity, as shown for example by Tabata et al [72] for photocatalytic water splitting over K4Nb6O17. Further, according to Bloh [73] this implies that the reaction over NiO/La-NTO is purely governed by the photon flux and effects like mass-transfer limitations can be neglected.…”

Section: Full Lamp Light Spectrummentioning

confidence: 95%

Figures of Merit for Photocatalysis: Comparison of NiO/La-NaTaO3 and Synechocystis sp. PCC 6803 as a Semiconductor and a Bio-Photocatalyst for Water Splitting

et al. 2021

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While photocatalysis is considered a promising sustainable technology in the field of heterogeneous catalysis as well as biocatalysis, figures of merit (FOM) for comparing catalytic performance, especially between disciplines, are not well established. Here, photocatalytic water splitting was conducted using a semiconductor (NiO/La-NaTaO3) and a bio-photocatalyst (Synechocystis sp. PCC 6803) in the same setup under similar reaction conditions, eliminating the often ill-defined influence of the setup on the FOMs obtained. Comparing the results enables the critical evaluation of existing FOMs and a quantitative comparison of both photocatalytic systems. A single FOM is insufficient to compare the photocatalysts, instead a combination of multiple FOMs (reaction rate, photocatalytic space time yield and a redefined apparent quantum yield) is superior for assessing a variety of photocatalytic systems.

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“…Some reaction models suggest that the reaction order for light intensity decreases from one to one-half with increasing light intensity. 31,32 The quantum efficiency of the reaction also decreases as water splitting rates deviate downward from a proportional relationship. This is because charge recombination is a second-order reaction with respect to carrier concentrations and accelerates nonlinearly with increasing light intensity.…”

Section: Apparent Activation Energymentioning

confidence: 99%

Kinetic Assessment and Numerical Modeling of Photocatalytic Water Splitting toward Efficient Solar Hydrogen Production

Hisatomi

Minegishi

Domen

2012

Bulletin of the Chemical Society of Japan

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Photocatalytic water splitting has been studied extensively as a promising technology for scalable and cost-efficient hydrogen production using solar energy. Although overall water splitting has been achieved under visible light irradiation, significant progress in reaction efficiencies at longer wavelengths is needed to enable practical solar energy conversion. This article reports recent advancements in kinetic investigation and numerical modeling of photocatalytic water splitting to understand problems with existing photocatalysts and develop strategies to boost the reaction efficiency. Kinetic investigation based on cocatalyst loading, light intensity, hydrogen/deuterium isotopes, and reaction temperature suggests that the majority of photoexcited carriers recombine before contributing to the water splitting reaction on the surface in most cases, and that improvement in semiconducting properties of photocatalysts by decreasing defect and donor concentrations is beneficial to boost photocatalytic performance. It is demonstrated that an appropriate material design to suppress generation of donor species actually improves photocatalytic activity. Numerical modeling of steady state carrier concentrations suggests that an asymmetric built-in potential in photocatalyst particles enhances charge separation and thus extends the lifetimes of photoexcited carriers. On the basis of the recent findings, we suggest strategies to improve the reaction efficiency of photocatalytic water splitting.

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Light-intensity dependence in photocatalytic decomposition of water over K4Nb6O17 catalyst

Cited by 34 publications

References 13 publications

Effect of Bed Height on the Performance of a Fixed Mo/HZSM‐5 Bed in Direct Aromatization of Methane

Effect of Bed Height on the Performance of a Fixed Mo/HZSM‐5 Bed in Direct Aromatization of Methane

Figures of Merit for Photocatalysis: Comparison of NiO/La-NaTaO3 and Synechocystis sp. PCC 6803 as a Semiconductor and a Bio-Photocatalyst for Water Splitting

Kinetic Assessment and Numerical Modeling of Photocatalytic Water Splitting toward Efficient Solar Hydrogen Production

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