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- 作者：Haimei Liu ; Akihito Imanishi ; Yoshihiro Nakato
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：April 17, 2008
- 年：2008
- 卷：112
- 期：15
- 页码：6211 - 6211
- 全文大小：10K
- 年卷期：v.112,no.15(April 17, 2008)
- ISSN：1932-7455
文摘
We present a modular approach to the synthesis of nanostructured catalysts for photochemical splitting ofwater into hydrogen and oxygen. The catalysts are built from exfoliated, semiconducting niobate nanosheetsderived from the layered perovskite HCa2Nb3O10. The latter is a catalyst for photochemical evolution ofhydrogen from water under UV irradiation. After chemical modification with 3-aminopropyltrimethoxysilane(APS), IrO2 or Pt particles can be attached to the nanosheets to produce various two-component nanostructuresthat were fully characterized with transmission electron microscopy and ultraviolet and infrared spectroscopy.Cyclic voltammetry was used to determine the onset potentials for O2 and H2 evolution. At pH = 14, theobserved values are in the range +0.61 to +1.24 V (NHE, water oxidation) and -1.36 to -1.62 V (NHE,water reduction). Under UV irradiation, all catalysts evolve hydrogen from water without any sign ofdeactivation for 5 h. The highest quantum efficiency of 3.49% is observed for a structure with Pt directlygrown onto the nanosheets. No O2 is evolved, which we attribute to the adsorption of O2 to the catalystsurface. For Pt-[HCa2Nb3O10], this process starts to shut down H2 evolution after 9 h of constant irradiation,but the activity can be restored to >60% by evacuating the catalyst dispersion and purging it with Ar. Catalystsassembled from preformed citrate-coated Pt nanoparticles are slightly less active for H2 evolution and so arecatalysts that use the linker aminoethyl-aminoundecanetrimethoxysilane (AEAUS) instead of APS. The activityof IrO2-APS-[Ca2Nb3O10] is lowest among two component catalysts, near the activities of the pure or APS-modified nanosheets. On the basis of XPS data, IrO2 in this catalyst undergoes photochemical reduction toIr(0) upon UV irradiation.