Hydrogen Production from Methane and Water on Platinum Loaded Titanium Oxide Photocatalysts
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- 作者：Hisao Yoshida ; Kazuhisa Hirao ; Jun-ichi Nishimoto ; Katsuya Shimura ; Satoru Kato ; Hideaki Itoh ; Tadashi Hattori
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：April 10, 2008
- 年：2008
- 卷：112
- 期：14
- 页码：5542 - 5551
- 全文大小：176K
- 年卷期：v.112,no.14(April 10, 2008)
- ISSN：1932-7455
文摘
Photocatalytic reaction of CH4 gas with H2O vapor was examined over Pt/TiO2 around room temperature (ca.323 K) in a flow reactor. H2 and CO2 were the main products, and only trace amounts of C2H6 and CO werealso observed. After an induction period, the molar ratio of H2 to CO2 in the outlet gas became close to 4.Thus, the main reaction is suggested as the equation CH4 + 2H2O(g) 
4H2 + CO2, which can be referredto as photocatalytic steam reforming of methane (photocatalytic SRM), where the photoenergy is convertedto chemical potential of products (
= 113 kJ mol-1). The reaction would be promoted byphotoexcited electrons and holes, which were generated by band gap photoexcitation of the TiO2 photocatalyst.The apparent quantum yield in the range 345-385 nm with high-intensity light (60 mW cm-2) was 0.6%,while the one in the range 240-270 nm with low-intensity light (2 mW cm-2) reached 2%. Highly activePt/TiO2 photocatalysts consisted of anatase phase TiO2 having large surface area and enough loading amount(more than 0.1 wt %) of metallic Pt nanosized particles, which should be loaded by the photodepositionmethod, preferentially in the reaction condition. During the induction period, the photoirradiated side of thecatalyst in the reaction cell turned pale brown, and the reaction was much accelerated. The colored surfacesubstances accelerating the reaction rate, whose chemical formula can be described as [CH2O]n, were revealedas the reaction intermediates. The reaction mechanism was also investigated.
4H2 + CO2, which can be referredto as photocatalytic steam reforming of methane (photocatalytic SRM), where the photoenergy is convertedto chemical potential of products ( = 113 kJ mol-1). The reaction would be promoted byphotoexcited electrons and holes, which were generated by band gap photoexcitation of the TiO2 photocatalyst.The apparent quantum yield in the range 345-385 nm with high-intensity light (60 mW cm-2) was 0.6%,while the one in the range 240-270 nm with low-intensity light (2 mW cm-2) reached 2%. Highly activePt/TiO2 photocatalysts consisted of anatase phase TiO2 having large surface area and enough loading amount(more than 0.1 wt %) of metallic Pt nanosized particles, which should be loaded by the photodepositionmethod, preferentially in the reaction condition. During the induction period, the photoirradiated side of thecatalyst in the reaction cell turned pale brown, and the reaction was much accelerated. The colored surfacesubstances accelerating the reaction rate, whose chemical formula can be described as [CH2O]n, were revealedas the reaction intermediates. The reaction mechanism was also investigated.