Facile cd-thiourea complex thermolysis synthesis of phase-controlled CdS nanocrystals for photocatalytic hydrogen production under visible light
Facile cd-thiourea complex thermolysis synthesis of phase-controlled CdS nanocrystals for photocatalytic hydrogen production under visible light
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DOI：
10.1021/jp076566s
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发表时间：
2007-11-29
影响因子：
3.7
通讯作者：
Grimes, Craig A.
中科院分区：
文献类型：
--
作者：
Bao, Ningzhong;Shen, Liming;Grimes, Craig A.
我们描述了一种简单的镉-硫脲络合物热分解方法来形成具有可控分散性、晶相、成分、平均颗粒尺寸和带隙的硫化镉纳米晶。比较了不同硫化镉产品的可见光驱动光催化制氢活性。通过改变硫脲与镉的比例或改变热处理温度，优化了所得到的硫化镉纳米晶的相结构和组成。在150-500℃的较宽的热处理温度范围内，硫脲/镉的摩尔比分别为1.0、1.5-2.5和3.0-4.5时，得到立方、立方和六方的混合物或六方的硫化镉纳米晶。纳米晶立方硫化镉在500℃下0.5h是稳定的，在超过1h的时间内转变为六方硫化镉。立方相变到六方相在200-300℃之间发生，在600℃以上的热处理温度下形成纯的六方硫化镉。与纯立方或六方硫化镉相比，立方硫化镉和六方硫化镉的混合物的光催化活性有所提高。结晶度好、粒径很小的近单分散六方硫化镉有望在可见光下提供最高的光催化制氢活性。
We describe a simple cadmium-thiourea complex thermolysis route for the formation of CdS nanocrystals with 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 the ratio of thiourea to Cd or by changing the annealing temperature. Over a broad annealing temperature range of 150-500 degrees C, either cubic, a mixture of cubic and hexagonal, or hexagonal CdS nanocrystals are obtained at thiourea/Cd molar ratios of < 1.0, 1.5-2.5, and 3.0-4.5, respectively. Nanocrystalline cubic CdS is stable at temperatures as high as 500 degrees C for 0.5 h, and is converted to hexagonal CdS for annealing time longer than I h. The phase transition from cubic to hexagonal CdS occurs at temperatures of 200-300 degrees C, and pure hexagonal CdS is formed at annealing temperatures higher than 600 degrees C. The dispersity, crystallinity, and average grain size of the CdS nanocrystals has been determined as a function of annealing temperature and time. Increased photocatalytic activity is observed from the mixture of cubic and hexagonal CdS as compared to pure cubic or hexagonal CdS. Nearly monodisperse hexagonal CdS with good crystallinity and very fine particle size is expected to offer the highest photocatalytic activity for hydrogen production under visible light.