Morphology-dependent catalytic properties of nanocupric oxides in the Rochow reaction

Four kinds of CuO catalysts with well-controlled leaf-like (L-CuO), flower-like (F-CuO), sea-urchin-like (U-CuO), and oatmeal-like (O-CuO) morphologies were synthesized by a facile precipitation method assisted by various chelating ligands. High-resolution transmission electron microscopy and fast Fourier transform infrared spectroscopy indicated that the dominant crystal facets of L-CuO, F-CuO, U-CuO, and O-CuO were {001}, {(1) over bar 10}, {001}, and {110}, as well as {001} and {(1) over bar 10}, respectively. When tested for the Rochow reaction, it was found that their catalytic performances were dependent on their structures. Among the four CuO catalysts, L-CuO exhibited the best catalytic property, along with the strongest adsorption ability for oxygen and highest reducibility, which are mainly because of its largely exposed {001} facet and large specific surface area. In addition, the amount of the Cu3Si alloy phase, which is the most important reaction intermediate that generated in the reacted region of the Si surface, was measured for the different catalysts. Based on the findings, a detailed reaction mechanism was proposed. This work demonstrates that shape-controlled synthesis of oxide catalysts could be an effective strategy to design and develop efficient catalysts.