Aspects of the water splitting mechanism on (Ga 1-xZn x)(N 1-xO x) photocatalyst modified with Rh 2-yCr yO 3 cocatalyst

Takashi Hisatomi; Kazuhiko Maeda; Kazuhiro Takanabe; Jun Kubota; Kazunari Domen

doi:10.1021/jp9079662

Aspects of the water splitting mechanism on (Ga _1-xZn _x)(N _1-xO _x) photocatalyst modified with Rh _2-yCr _yO ₃ cocatalyst

Takashi Hisatomi, Kazuhiko Maeda, Kazuhiro Takanabe, Jun Kubota, Kazunari Domen^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

138 Scopus citations

Abstract

Aspects of the water splitting mechanism on (Ga _1-xZn _x)(N _1-xO _x) photocatalyst powder are discussed on the basis of the effects of cocatalyst loading, light intensity, hydrogen/deuterium isotopes, and reaction temperature on photocatalytic activity. The loading amount of Rh _2-yCr _yO ₃ cocatalyst significantly affected the photocatalytic behavior with varying light intensity. When the loading amount of Rh _2-yCr _yO ₃ as a H ₂ evolution cocatalyst was insufficient, the reaction order for light intensity was lower than unity. This is because photoexcited electrons accumulated in the photocatalyst and recombined with photoexcited holes more frequently than they contributed to the water splitting reaction. When a sufficient amount of cocatalyst was loaded, on the other hand, accumulation of photoexcited electrons was suppressed and the water splitting rate increased monotonically with light intensity. At a light intensity equivalent to solar irradiation, AM1.5, the water splitting rate using modified (Ga _1-xZn _x)(N _1-xO _x) remained under the light-intensity-proportional regime. The isotope effect of H ₂O/D ₂O on overall water splitting using Rh _2-yCr _yO ₃/(Ga _1-xZn _x)(N _1-xO _x) was smaller than previously reported for electrochemical H ₂ evolution reactions. Moreover, the apparent activation energy of the overall water splitting was as small as 8 kJ mol ^-1, and independent of the reactants. These results arise from the limited number of photoexcited carriers present in the Rh _2-yCr _yO ₃/(Ga _1-xZn _x)(N _1-xO _x), which should become available for redox reactions on the surface of the photocatalyst. A kinetic model of photocatalytic water splitting proposed in this work suggests that the reaction probability of photoexcited holes for O ₂ evolution versus recombination with intrinsic electrons of the photocatalyst determines the photocatalytic activity of the Rh _2-yCr _yO ₃/(Ga _1-xZn _x)(N _1-xO _x).

Original language	English (US)
Pages (from-to)	21458-21466
Number of pages	9
Journal	JOURNAL OF PHYSICAL CHEMISTRY C
Volume	113
Issue number	51
DOIs	https://doi.org/10.1021/jp9079662
State	Published - 2009
Externally published	Yes

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
General Energy
Physical and Theoretical Chemistry
Surfaces, Coatings and Films

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10.1021/jp9079662

Cite this

@article{cc09ccad1a824b6ba3aa2eb0e080e5c0,

title = "Aspects of the water splitting mechanism on (Ga 1-xZn x)(N 1-xO x) photocatalyst modified with Rh 2-yCr yO 3 cocatalyst",

abstract = "Aspects of the water splitting mechanism on (Ga 1-xZn x)(N 1-xO x) photocatalyst powder are discussed on the basis of the effects of cocatalyst loading, light intensity, hydrogen/deuterium isotopes, and reaction temperature on photocatalytic activity. The loading amount of Rh 2-yCr yO 3 cocatalyst significantly affected the photocatalytic behavior with varying light intensity. When the loading amount of Rh 2-yCr yO 3 as a H 2 evolution cocatalyst was insufficient, the reaction order for light intensity was lower than unity. This is because photoexcited electrons accumulated in the photocatalyst and recombined with photoexcited holes more frequently than they contributed to the water splitting reaction. When a sufficient amount of cocatalyst was loaded, on the other hand, accumulation of photoexcited electrons was suppressed and the water splitting rate increased monotonically with light intensity. At a light intensity equivalent to solar irradiation, AM1.5, the water splitting rate using modified (Ga 1-xZn x)(N 1-xO x) remained under the light-intensity-proportional regime. The isotope effect of H 2O/D 2O on overall water splitting using Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x) was smaller than previously reported for electrochemical H 2 evolution reactions. Moreover, the apparent activation energy of the overall water splitting was as small as 8 kJ mol -1, and independent of the reactants. These results arise from the limited number of photoexcited carriers present in the Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x), which should become available for redox reactions on the surface of the photocatalyst. A kinetic model of photocatalytic water splitting proposed in this work suggests that the reaction probability of photoexcited holes for O 2 evolution versus recombination with intrinsic electrons of the photocatalyst determines the photocatalytic activity of the Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x).",

author = "Takashi Hisatomi and Kazuhiko Maeda and Kazuhiro Takanabe and Jun Kubota and Kazunari Domen",

year = "2009",

doi = "10.1021/jp9079662",

language = "English (US)",

volume = "113",

pages = "21458--21466",

journal = "JOURNAL OF PHYSICAL CHEMISTRY C",

issn = "1932-7447",

publisher = "American Chemical Society",

number = "51",

}

TY - JOUR

T1 - Aspects of the water splitting mechanism on (Ga 1-xZn x)(N 1-xO x) photocatalyst modified with Rh 2-yCr yO 3 cocatalyst

AU - Hisatomi, Takashi

AU - Maeda, Kazuhiko

AU - Takanabe, Kazuhiro

AU - Kubota, Jun

AU - Domen, Kazunari

PY - 2009

Y1 - 2009

N2 - Aspects of the water splitting mechanism on (Ga 1-xZn x)(N 1-xO x) photocatalyst powder are discussed on the basis of the effects of cocatalyst loading, light intensity, hydrogen/deuterium isotopes, and reaction temperature on photocatalytic activity. The loading amount of Rh 2-yCr yO 3 cocatalyst significantly affected the photocatalytic behavior with varying light intensity. When the loading amount of Rh 2-yCr yO 3 as a H 2 evolution cocatalyst was insufficient, the reaction order for light intensity was lower than unity. This is because photoexcited electrons accumulated in the photocatalyst and recombined with photoexcited holes more frequently than they contributed to the water splitting reaction. When a sufficient amount of cocatalyst was loaded, on the other hand, accumulation of photoexcited electrons was suppressed and the water splitting rate increased monotonically with light intensity. At a light intensity equivalent to solar irradiation, AM1.5, the water splitting rate using modified (Ga 1-xZn x)(N 1-xO x) remained under the light-intensity-proportional regime. The isotope effect of H 2O/D 2O on overall water splitting using Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x) was smaller than previously reported for electrochemical H 2 evolution reactions. Moreover, the apparent activation energy of the overall water splitting was as small as 8 kJ mol -1, and independent of the reactants. These results arise from the limited number of photoexcited carriers present in the Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x), which should become available for redox reactions on the surface of the photocatalyst. A kinetic model of photocatalytic water splitting proposed in this work suggests that the reaction probability of photoexcited holes for O 2 evolution versus recombination with intrinsic electrons of the photocatalyst determines the photocatalytic activity of the Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x).

AB - Aspects of the water splitting mechanism on (Ga 1-xZn x)(N 1-xO x) photocatalyst powder are discussed on the basis of the effects of cocatalyst loading, light intensity, hydrogen/deuterium isotopes, and reaction temperature on photocatalytic activity. The loading amount of Rh 2-yCr yO 3 cocatalyst significantly affected the photocatalytic behavior with varying light intensity. When the loading amount of Rh 2-yCr yO 3 as a H 2 evolution cocatalyst was insufficient, the reaction order for light intensity was lower than unity. This is because photoexcited electrons accumulated in the photocatalyst and recombined with photoexcited holes more frequently than they contributed to the water splitting reaction. When a sufficient amount of cocatalyst was loaded, on the other hand, accumulation of photoexcited electrons was suppressed and the water splitting rate increased monotonically with light intensity. At a light intensity equivalent to solar irradiation, AM1.5, the water splitting rate using modified (Ga 1-xZn x)(N 1-xO x) remained under the light-intensity-proportional regime. The isotope effect of H 2O/D 2O on overall water splitting using Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x) was smaller than previously reported for electrochemical H 2 evolution reactions. Moreover, the apparent activation energy of the overall water splitting was as small as 8 kJ mol -1, and independent of the reactants. These results arise from the limited number of photoexcited carriers present in the Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x), which should become available for redox reactions on the surface of the photocatalyst. A kinetic model of photocatalytic water splitting proposed in this work suggests that the reaction probability of photoexcited holes for O 2 evolution versus recombination with intrinsic electrons of the photocatalyst determines the photocatalytic activity of the Rh 2-yCr yO 3/(Ga 1-xZn x)(N 1-xO x).

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