Nickel-loaded K sub 4 Nb sub 6 O sub 17 photocatalyst in the decomposition of H sub 2 O into H sub 2 and O sub 2 : Structure and reaction mechanism

Journal Article · Fri Dec 01 00:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90274-1· OSTI ID:7080493

Kudo, A; Sayama, K; Domen, K; Maruya, K; Onishi, T ^[1]; Tanaka, A ^[2]; Asakura, K ^[3]

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1. Tokyo Institute of Technology, Nagatsuta, Yokohama (Japan)
2. Nikon Company, Sagamihara (Japan)
3. The Univ. of Tokyo, Tokyo (Japan)

The structure of nickel-loaded K{sub 4}Nb{sub 6}O{sub 17} photocatalyst in an overall water splitting reaction was studied by means of XPS, EXAFS, TEM, and XRD. K{sub 4}Nb{sub 6}O{sub 17} has an ion-exchangeable layered structure which possesses two different kinds of alternating interlayer spaces, i.e. interlayers I and II, where K{sup +} ions are located. The interlayers are hydrated in an aqueous solution. It was revealed that in the active catalyst which was pretreated by H{sub 2} at 773 K for 2 h and reoxidized by O{sub 2} at 473 K for 1 h, loaded nickel is predominantly located in interlayer 1 as ultrafine metal particles (ca. 5 A). In contrast only a small amounnt of nickel was observed over the external surface of K{sub 4}Nb{sub 6}O{sub 17}. On the basis of the structure, a novel mechanism for the photodecomposition of H{sub 2}O into H{sub 2} and O{sub 2} is proposed; i.e., intercalated water is reduced to H{sub 2} in interlayer I and is oxidized to O{sub 2} in interlayer II. Therefore, each niobate macroanion sheet is regarded as a two-dimensional photocatalyst where H{sub 2} and O{sub 2} evolve at different sides of the layer.

• OSTI ID: 7080493
• Journal Information: Journal of Catalysis; (USA), Vol. 120:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
CATALYSTS
MICROSTRUCTURE
HYDROGEN PRODUCTION
PHOTOCHEMICAL REACTIONS
NICKEL
CATALYTIC EFFECTS
NIOBIUM OXIDES
POTASSIUM OXIDES
WATER
DECOMPOSITION
CATALYSIS
CHEMICAL PROPERTIES
CHEMICAL REACTION KINETICS
LAYERS
PHOTOELECTRON SPECTROSCOPY
SURFACE PROPERTIES
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY
ALKALI METAL COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTAL STRUCTURE
DIFFRACTION
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELEMENTS
HYDROGEN COMPOUNDS
KINETICS
METALS
MICROSCOPY
NIOBIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
SCATTERING
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
080106* - Hydrogen- Production- Biosynthesis & Photochemical Processes