Photocatalytic properties of gallium oxides prepared by precipitation methods toward the overall splitting of H2O

Sakata, Yoshihisa; Nakagawa, Takaki; Nagamatsu, Yasuhiro; Matsuda, Yuta; Yasunaga, Ryō; Nakao, Emi; Imamura, Hayao

doi:10.1016/j.jcat.2013.06.025

Cited by 39 publications

(36 citation statements)

References 26 publications

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“…Please note that the optimal AQYs for α-and β-Ga2O3 (both loaded with Rh0.5Cr1.5O3) at 254 nm were 10% and 24%, respectively. 19 The optimal AQY for γ-Ga2O3 in this study is 8.34% and close to the above values. As we observed the much higher absolute H2 evolution rate for γ-Ga2O3 than other two polymorphs, we believe the AQY for γ-Ga2O3 could be further enhanced, probably by increasing the beam density and/or appropriate loading of other cocatalysts.…”

Section: Photocatalytic Performancessupporting

confidence: 85%

Photocatalytic H₂ evolution for α-, β-, γ-Ga₂O₃ and suppression of hydrolysis of γ-Ga₂O₃ by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Xie

et al. 2016

RSC Adv.

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In contrast to that α-, β-Ga2O3 were already studied as photocatalysts for pure water splitting, there was no report on the γ-phase. A comparative study on α-, β-and γ-Ga2O3 all prepared by precipitation method were therefore performed. The as-prepared gallium oxides were phaseidentified by powder X-ray diffraction, where γ-Ga2O3 possessed the most broad reflection peaks due to the poor crystallization. Scanning electron microscopy and N2 adsorption-desorption experiments confirmed the morphology, and the specific surface areas were 144.3, 77.3, 33.7 m 2 /g for γ-, β-and α-Ga2O3, respectively. Photocatalytic H2 evolution efficiency in pure water were evaluated to be in the order of γ-Ga2O3 > β-Ga2O3 > α-Ga2O3, which were all much higher than that of P25-1 wt% Ag. A slight hydrolysis process was observed for γ-Ga2O3, both lowing pH value (~ 4.5) by H2SO4 and adding sacrificial agent (CH3OH) were applied to prohibit the hydrolysis completely, eventually, 1 wt% Ag was loaded as the cocatalyst in order to not only improve the stability and also increase the H2 generation rate to 742 μmol/h/g in pure water. In addition, for this particular photocatalyst, the optimal apparent quantum yield at 254 nm achieved 8.34%. Our work represents the first study of γ-Ga2O3 in the application of photocatalytic water splitting, and indeed it might have a high potential in the solar energy conversion.

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Section: Photocatalytic Performancessupporting

confidence: 85%

Photocatalytic H₂ evolution for α-, β-, γ-Ga₂O₃ and suppression of hydrolysis of γ-Ga₂O₃ by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Xie

et al. 2016

RSC Adv.

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“…In contrast to the situation with Rh 0.5 Cr 1.5 O 3 as the cocatalyst, the γ-Ga 2 O 3 photocatalyst shows a higher normalized activity than the β-Ga 2 O 3 photocatalyst, which can be ascribed to the matched degree between Ga 2 O 3 material and cocatalyst. 30 However, the γ/β-Ga 2 O 3 -10% photocatalyst still shows the lowest photocatalytic overall water splitting activity ( Figure S1). Therefore, the lowest activity for the γ/β-Ga 2 O 3 -10% photocatalyst and the variation tendency of photocatalytic activity cannot be just ascribed to the difference in relative amount of γ and β phases, but must be associated with the intrinsic phase property of 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The situation for the γ/β-Ga 2 O 3 system is vastly different from that for the reported α/β-Ga 2 O 3 system.…”

Section: Resultsmentioning

confidence: 98%

Effect of Phase Junction Structure on the Photocatalytic Performance in Overall Water Splitting: Ga₂O₃ Photocatalyst as an Example

et al. 2015

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The fabrication of surface phase junctions has proven to be an efficient strategy for the enhancement of photocatalytic activity, however, some questions about these systems are not yet well understood. In this study, the photocatalytic overall water splitting reaction was achieved on photocatalysts with pure and mixed phase compositions of cubic γ-Ga 2 O 3 and monoclinic β-Ga 2 O 3 . All the Ga 2 O 3 photocatalysts can split water stoichiometrically into H 2 and O 2 , however, the phase-mixed γ/β-Ga 2 O 3 photocatalyst with a small amount of β phase shows the lowest activity. This is opposite from that of the reported α/β-Ga 2 O 3 system, in which the phase-mixed α/β-Ga 2 O 3 photocatalyst with a small amount of β phase shows much higher photocatalytic activity than the individual phases. Much more disordered structure is found between the γ and β phases in the γ/β-Ga 2 O 3 photocatalyst with low content of β phase due to the defective spinel structure of γ phase. Spectroscopic

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“…Due to the difference in microstructure, different crystalline phases show the large differences in the physical and chemical properties, such as the catalytic performance [103][104][105]. As catalytic reactions take place on the surface of metal oxide catalysts, catalytic performance is closely related to the surface phase structure of catalyst.…”

Section: Uv Raman Spectroscopic Study On the Phase Transformation Ofmentioning

confidence: 99%

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

et al. 2014

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UV Raman spectroscopy has been demonstrated to be a powerful technique in catalysis because it can avoid the fluorescence interference occurring in visible Raman spectroscopy and concurrently enhance the Raman scattering intensity owing to the short wavelength of the excitation laser and resonance Raman effect. This article briefly reviews the recent advances in the study on heterogeneous catalysis by UV Raman spectroscopy, including the identification of isolated transition metal ions in molecular sieves, in situ study of zeolite assembly mechanisms and catalytic reaction mechanisms, and the monitoring of the surface phase transformation of metal oxide photocatalysts. UV (resonance) Raman spectroscopy, with the power of resonance enhancement for Raman signal and the advantage of high sensitivity for surface structure, coupling with in situ methodology, can provide the information about the active sites/phase and their assembling mechanisms, which are helpful for the understanding of heterogeneous catalysis and the rational design of highly active and selective catalysts.

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Photocatalytic properties of gallium oxides prepared by precipitation methods toward the overall splitting of H2O

Cited by 39 publications

References 26 publications

Photocatalytic H₂ evolution for α-, β-, γ-Ga₂O₃ and suppression of hydrolysis of γ-Ga₂O₃ by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Photocatalytic H₂ evolution for α-, β-, γ-Ga₂O₃ and suppression of hydrolysis of γ-Ga₂O₃ by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Effect of Phase Junction Structure on the Photocatalytic Performance in Overall Water Splitting: Ga₂O₃ Photocatalyst as an Example

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

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Photocatalytic properties of gallium oxides prepared by precipitation methods toward the overall splitting of H2O

Cited by 39 publications

References 26 publications

Photocatalytic H2 evolution for α-, β-, γ-Ga2O3 and suppression of hydrolysis of γ-Ga2O3 by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Photocatalytic H2 evolution for α-, β-, γ-Ga2O3 and suppression of hydrolysis of γ-Ga2O3 by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Effect of Phase Junction Structure on the Photocatalytic Performance in Overall Water Splitting: Ga2O3 Photocatalyst as an Example

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

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Photocatalytic H₂ evolution for α-, β-, γ-Ga₂O₃ and suppression of hydrolysis of γ-Ga₂O₃ by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Photocatalytic H₂ evolution for α-, β-, γ-Ga₂O₃ and suppression of hydrolysis of γ-Ga₂O₃ by adjusting pH, adding a sacrificial agent or loading a cocatalyst

Effect of Phase Junction Structure on the Photocatalytic Performance in Overall Water Splitting: Ga₂O₃ Photocatalyst as an Example