Shape-Controlled Synthesis And Catalytic Properties Of Copper Oxides And Sulfides By Hydrothermal Methods

It is well known that the size, morphology of inorganic micro- and nanostructures can significantly affect their physical and chemical properties. The micro- and nanostructures shape-control is one of the most important research points. There are two kinds of shape control methods: controlling the growth kinetics and using a template. Here,we use these two methods to achieve shape control and get some new results.We reported a facile microwave-assisted heating technique for the synthesis of Cu2 O microcrystals with systematic shape evolution. Monodisperse octahedral, truncated octahedral, cuboctahedral, truncated cubic and cubic microcrystals were synthesized directly by varying water/butyl alcohol ratio in the reaction solvent. The dielectric losses of water and n-butyl alcohol were used to calculate the heating efficiency of the reaction medium. The higher dielectric loss results in higher heating efficiency. Due to the different dielectric losses of water and n-butyl alcohol, the heating efficiency of the reaction medium changed with the varying of n-butyl alcohol/water volume ratio. The heating efficiency seems to determine the growth rates of different crystal directions and thus affect the morphologies of Cu2 O. The shape of Cu2 O microcrystal evolved sequentially from a perfect octahedral, a type I truncated octahedra, a type II truncated octahedra, a cuboctahedra, a truncated cube to a perfect cube with the decreasing of the n-butyl alcohol/water volume ratios in the reaction medium. This is the first time to realize the shape-controlled synthesis of Cu2 O microcrystals with microwave assisted heating technique, which provides an informative example for developing new synthetic routes. The absorption abilities and photocatalytic activities of these Cu2 O microcrystals were investigated for the decomposition of MO under visible light irradiation. The results demonstrate that both octahedral and truncated octahedral Cu2 O particles have much higher activity than the other Cu2 O particles.A variety of multipod frameworks of Cu2 O microcrystals have been prepared through careful control of the volume ratios of n-butyl alcohol to water in the reaction solvent(such as 6-pods frameworks, type Ι 14-pods frameworks, type ΙΙ 6-pods frameworks and 8-pods frameworks). In particular, 14-pods Cu2 O frameworks were first prepared. These results provide a facile procedure for the controlled preparation of novel multi-morphologic Cu2 O microcrystals. Moreover, a template-assisted synthesis of multipod frameworks of Cu7S4 microcages using the obtained Cu2 O microcrystals as sacrificial templates was established. This study revealed an important strategy in the design, controlled crystal growth, and morphology-controlled synthesis of multipod frameworks of Cu2 O microcrystals and Cu7S4 microcages. It will also promote the synthesis and application of other inorganic building blocks. The absorption abilities and photocatalytic activities of these Cu7S4 microcages were investigated for the decomposition of MB under visible light irradiation. The 14-pods Cu7S4 microcages exhibit higher photocatalytical activities than the 6-pods Cu7S4 microcages.The 14-pods Cu7S4 microcages wholly exposed with nanotwinned building blocks were successfully achieved via an ethanol-assisted sacrificial Cu2 O templates approach. Photocatalytic degradation of MB demonstrated that the Cu7S4 microcages with nanotwinned building blocks exhibited catalytic activity higher than that the Cu7S4 microcages without nanotwinned structures, attributed to their special nanotwinned components. Because the nanotwins inside the Cu7S4 cages might keep the transport property of free charges as in perfect crystals, and could decrease the recombination of photoinduced electrons and holes, and increase the lifetime of the electron–hole pairs. This study is of great importance in the synthesis of high-active hollow architectures, and the formation of these unusual 14-pods Cu7S4 hollow cages not only enriches the family of copper sulfide architectures, but also offers a good opportunity to understand the fundamental significance of nanotwinned structures. It is expected that hollow cages with nanotwinned building blocks will provide an efficient approach for the investigation of their potential applications in other fields(including electrics, optics, sensors and so forth).In a word, both the microwave-assisted heating technique and hydrothermal methods, employed in this paper, are all green and low-energy approaches for the shape-control synthesis of Cu2 O microcrystals with various morphologies. Moreover, a template-assisted synthesis of multipod frameworks of Cu7S4 microcages and Cu7S4 hollow cages with nanotwinned building blocks using the obtained Cu2 O microcrystals as sacrificial templates was established. At the same time, the corresponding absorption abilities and photocatalytic activities of these Cu2 O microcrystals and Cu7S4 hollow cages were investigated 。...