Facile Cd-Thiourea Complex Thermolysis Synthesis of Phase-Controlled CdS Nanocrystals for Photocatalytic Hydrogen Production under Visible Light

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• 作者：Ningzhong Bao ; Liming Shen ; Tsuyoshi Takata ; Kazunari Domen ; Arunava Gupta ; Kazumichi Yanagisawa ; Craig A. Grimes
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：November 29, 2007
• 年：2007
• 卷：111
• 期：47
• 页码：17527 - 17534
• 全文大小：510K
• 年卷期：v.111,no.47(November 29, 2007)
• ISSN：1932-7455

文摘

We describe a simple cadmium-thiourea complex thermolysis route for the formation of CdS nanocrystalswith controlled dispersity, crystalline phase, composition, average grain size, and band gap. Visible-light-driven photocatalytic activities for hydrogen production over the different CdS products have been compared.Phase structure and composition of the obtained CdS nanocrystals has been optimized either by changing theratio of thiourea to Cd or by changing the annealing temperature. Over a broad annealing temperature rangeof 150-500 C, either cubic, a mixture of cubic and hexagonal, or hexagonal CdS nanocrystals are obtainedat thiourea/Cd molar ratios of <1.0, 1.5-2.5, and 3.0-4.5, respectively. Nanocrystalline cubic CdS is stableat temperatures as high as 500 C for 0.5 h, and is converted to hexagonal CdS for annealing time longerthan 1 h. The phase transition from cubic to hexagonal CdS occurs at temperatures of 200-300 C, and purehexagonal CdS is formed at annealing temperatures higher than 600 C. The dispersity, crystallinity, andaverage grain size of the CdS nanocrystals has been determined as a function of annealing temperature andtime. Increased photocatalytic activity is observed from the mixture of cubic and hexagonal CdS as comparedto pure cubic or hexagonal CdS. Nearly monodisperse hexagonal CdS with good crystallinity and very fineparticle size is expected to offer the highest photocatalytic activity for hydrogen production under visiblelight.