Photoreactions on LaTiO<sub>2</sub>N under Visible Light Irradiation

Kasahara, Asako; Nukumizu, Kota; Hitoki, Go; Takata, Tsuyoshi; Kondo, Junko N.; Hara, Michikazu; Kobayashi, Hisayoshi; Domen, Kazunari

doi:10.1021/jp025961+

Cited by 457 publications

(364 citation statements)

References 12 publications

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“…36 0.1 g of LaTiO 2 N powder consists of approximately 3 © 10 10 particles, given an average particle size of 1¯m. Assuming that incident light is perfectly absorbed by 0.1 g of LaTiO 2 N, the rate of photoexcited carrier generation per particle (G) is equal to 1/(3 © 10 10 ) of the incident photon number (I Ph ).…”

Section: Quasi-fermi Levels Of Photocatalyst Particles Under Light Irmentioning

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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Section: Quasi-fermi Levels Of Photocatalyst Particles Under Light Irmentioning

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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“…23,25,[29][30][31][32] Cobalt oxide (CoO x ) has been extensively investigated as a cocatalyst, particularly for electrochemical and photoelectrochemical OER. 25,[29][30][31][32]34,35 Although many studies have reported improvement of the electrochemical OER using CoO x , studies on powder suspension systems are limited. To date, quantum efficiencies as high as 27% (at 440 nm) have been reported on CoO x /LaTiO 2 N for the OER in the presence of Ag + as a sacrificial reagent.…”

Section: Introductionmentioning

confidence: 99%

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

et al. 2015

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ABSTRACT:In a photocatalytic suspension system with a powder semiconductor, the interface between the photocatalyst semiconductor and catalyst should be constructed to minimize resistance for charge transfer of excited carriers. This study demonstrates an in-depth understanding of pretreatment effects on the photocatalytic O 2 evolution reaction (OER) activity of visible-lightresponsive Ta 3 N 5 decorated with CoO x nanoparticles. The CoO x /Ta 3 N 5 sample was synthesized by impregnation followed by sequential heat treatments under NH 3 flow and air flow at various temperatures. Various characterization techniques, including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS), were used to clarify the state and role of cobalt. No improvement in photocatalytic activity for OER over the bare Ta 3 N 5 was observed for the as-impregnated CoO x /Ta 3 N 5 , likely because of insufficient contact between CoO x and Ta 3 N 5 . When the sample was treated in NH 3 at high temperature, a substantial improvement in the photocatalytic activity was observed. After NH 3 treatment at 700 °C, the Co 0 -CoO x core-shell agglomerated cobalt structure was identified by XAS and STEM. No metallic cobalt species was evident after the photocatalytic OER, indicating that the metallic cobalt itself is not essential for the reaction. Accordingly, mild oxidation (200 °C) of the NH 3 -treated CoO x /Ta 3 N 5 sample enhanced photocatalytic OER activity. Oxidation at higher temperatures drastically eliminated the photocatalytic activity, most likely because of unfavorable Ta 3 N 5 oxidation. These results suggest that the intimate contact between cobalt species and Ta 3 N 5 facilitated at high temperature is beneficial to enhancing hole transport and that the cobalt oxide provides electrocatalytic sites for OER. IntroductionWater splitting using powder photocatalyst systems has attracted significant interest for the production of renewable hydrogen generation using abundant solar energy because of its simplicity, scalability, and low capital cost.1,2 To effectively convert solar energy, substantial utilization of photon energy in the visible-light range is essential. Using the AM 1.5G standard spectrum 3 , a photocatalyst with absorption from UV to 600 nm with a quantum efficiency of 30% accounts for ~5% solar to hydrogen efficiency, making the technology commercially feasible.1,4 Among the photocatalysts investigated to date, tantalum(V) nitride (Ta 3 N 5 ) has emerged as one of the most promising candidates and has been extensively investigated for more than a decade. [4][5][6][7][8][9][10][11][12][13][14][15] Ta 3 N 5 has a visible-light response (approximately 600 nm, ~2.1-eV band gap) and is capable of producing hydrogen or oxygen in the presence of appropriate sacrificial reagents and surface modifications under visible-light irradiation. 1,[5][6][7][8][9][10][11][12][13][14][15][16] Our recent work on Ta 3 N 5 thin films for the photo...

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“…[9] LaTiO 2 N, prepared following the Pechini method using a polymerized complex of La and Ti metal precursors followed by ammonolysis in a flow of ammonia, has been prepared and tested as an H 2 and O 2 generating photocatalyst from water in the presence of sacrificial reagents. [10] In addition, a wide range of oxynitrides such as TaON, [11] Ta 3 N 5 , [12,13] TaO x N y , [14] TiO 2-x N x , [15] (Zn 1+x Ge)(N 2 O x ) [16] have been studied as potential photocatalysts for water splitting, oxidation of methanol, and decomposition of organic pollutants. A variety of synthesis methods have been employed in synthesis as well as incorporation of N into metal oxide lattices.…”

Section: Introductionmentioning

confidence: 99%

Solution-phase Synthesis of Zn-doped GaN Photocatalysts: Morphology, Composition, and Catalytic Activity towards Methylene Blue Degradation and 4-nitroaniline Conversion

Senevirathne¹,

Pitigala²,

Ramaraj³

et al. 2017

AJN

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Solution based synthesis methods; refluxing, base hydrolysis, and hydrothermal synthesis were successfully applied to synthesize shape anisotropic Zn doped Ga 2 O 3 , followed by subsequent nitridation in ammonia to make corresponding nitride photocatalysts. The catalysts were characterized using different physical characterization methods to evaluate their structure, shape and composition. Photocatalytic methylene blue (MB) degradation and selective hydrogenation of aromatic nitro organic compound 4-nitroaniline (4-NA) were selected to probe reactions under uv-visible and visible light irradiation. Zn containing nitride catalysts are clearly active on MB degradation and 4-NA conversion under visible light irradiation.

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Photoreactions on LaTiO₂N under Visible Light Irradiation

Cited by 457 publications

References 12 publications

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

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

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

Solution-phase Synthesis of Zn-doped GaN Photocatalysts: Morphology, Composition, and Catalytic Activity towards Methylene Blue Degradation and 4-nitroaniline Conversion

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Photoreactions on LaTiO2N under Visible Light Irradiation

Cited by 457 publications

References 12 publications

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

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

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta3N5 Photocatalyst

Solution-phase Synthesis of Zn-doped GaN Photocatalysts: Morphology, Composition, and Catalytic Activity towards Methylene Blue Degradation and 4-nitroaniline Conversion

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Photoreactions on LaTiO₂N under Visible Light Irradiation

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst