Morphology-dependent catalytic properties of nanocupric oxides in Rochow reaction

Significance Statement

The preparation of micro, meso, and nanosized materials with a better control of their shape is of outmost importance. This is because each of their application is dependent on their physicochemical attributes along with morphologies. The idea of morphology-controlled preparation with an aim of tailoring performances of catalysts, battery anodes, and semiconducting gas sensors, has been the focus of research in the recent past.

A good number of the preparation techniques center on the control of the character of exposed crystallographic planes as well as grain and pore structure. In the recent years, steps have been made in the controlled preparation of nanosized catalysts, and to the in-depth understanding of the shape dependent catalytic attributes.

Morphology-modulated catalytic activity exhibited by some metal oxide nanostructures is necessary in catalysis since it provides a potential path for tuning the rate of reaction, the extent of reactivity, and the main products. Copper oxide is such a transition metal oxide that exhibits morphology-dependent catalytic activity. Copper oxide is also an effective catalyst in the Rochow reaction. This is the direct process implemented to synthesize methylchlorosilanes.

The Rochow reaction entails a typical gas-solid-solid system used in industrial processes. Owing to the complexity of the reaction, the actual role of the copper-based catalysts is yet to be fully understood. Researchers led by Professor Fabing Su and Yongjun Ji from the Chinese Academy of Sciences, China, prepared a series of copper oxide catalysts with varying morphologies through a solution-based precipitation method implementing various organic ligands, and tested them for the Rochow reaction. Their work is published in peer-reviewed journal, Nano Research.

The authors synthesized four forms of copper catalysts with controlled leaf like, flower like, oatmeal like, and sea urchin-like morphologies through a facile precipitation approach in conjunction with a number of chelating ligands. Through fast Fourier transform infrared spectroscopy and high resolution transmission electron microscopy, the authors found that the dominant crystal facets of the four copper oxide catalysts were [001], [110], [001], and [110] and [001] and [110] for the leaf like, flower like, sea urchin-like and oatmeal-like copper oxide, respectively.

The researchers also tested the catalyst for the Rochow reaction, and found that their catalytic activities were mainly dependent on their structures. Among the selected copper oxide catalysts, the leaf-like copper oxide indicated the best catalytic performance, strongest adsorption ability for oxygen, and excellent reducibility. These attributes could be attributed to its largely exposed [001] facet as well as large specific surface area.

The researchers also measured for various catalysts the amount of Cu3Si alloy phase that was the most necessary reaction intermediate, which yielded in the reacted region of the silicon surface. Based on the findings of the study, the authors proposed a detailed reaction mechanism.

This study indicated that shape-controlled preparation of oxide catalysts could be an effective path for designing and developing effective catalysts.

Morphology-dependent catalytic properties of nanocupric oxides in the Rochow reaction. Advances in Engineering
Leaf-like CuO that mainly exposes {001} crystal plane showed superior catalytic properties for dimethyldichlorosilane synthesis via the Rochow reaction owing to the maximum formation of Cu3Si alloy phase generated in the reacted region of Si surface.

About the author

Yu Zhang is currently a Ph.D student at Institute of Process Engineering (IPE), Chinese Academy of Sciences (CAS) under the supervision of Professor Fabing Su. She received her B.S. degree in Metallurgy Engineering from Central South University in 2014. Her on-going research is focused on synthesis, characterization and structural modification of copper-based catalyst for the Rochow reaction. She has first-authored three related peer-reviewed papers published in Journal of Catalysis (2 paper), and Nano Research (1 paper). She also has two invention patents pending.

About the author

Yongjun Ji obtained his Ph.D. (2012) in Physical Chemistry from East China Normal University in China, under the supervision of Prof. Peng Wu. After that, he joined Prof. Yadong Li’s group in Tsinghua University as a Postdoctoral Fellow in 2012-2014. Now, he is worked in Prof. Fabing Su’s group at the Institute of Process Engineering, Chinese Academy of Sciences as an associate professor. His research interests include controlled synthesis and characterization of zeolite and novel nanomaterials as well astheir application in heterogeneous catalysis.

Reference

Yu Zhang, Yongjun Ji*, Jing Li, Hezhi Liu, Xiao Hu, Ziyi Zhong, and Fabing Su. Morphology-dependent catalytic properties of nanocupric oxides in the Rochow reaction. Nano research DOI 10.1007/s12274-017-1689-x.

 

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