Impact of the Cu2O microcrystal planes on active phase formation in the Rochow reaction and an experimental and theoretical understanding of the reaction mechanism

In heterogeneous catalysis, on one hand, people always want to know about reaction details, such as what the most active phase is, how it is formed, and what is the reaction mechanism. On the other hand, it is still very challenging to probe these reaction details, particularly at high reaction temperatures and pressures. Here, we report the microcrystal plane-controlled catalytic performance on well-defined Cu2O cube, octahedron, and rhombic-dodecahedron catalysts in the Rochow reaction. It was found that the Cu2O cube exposing {100} crystal planes gave the highest dimethyldichlorosilane selectivity and yield, while the Cu2O rhombic-dodecahedron exposing {110} crystal planes showed the lowest selectivity and yield. Our experimental observation, as well as density functional theory calculations, demonstrated that the enhanced selectivity and yield stemmed from the stronger dissociative adsorption of methyl chloride on the Cu2O{100} plane, which greatly promoted the transformation of Cu2O into Cu3Si active phases under the reaction conditions. This work reveals a new strategy for controlling the surface structure of catalysts in order to enhance their catalytic performance. (C) 2018 Elsevier Inc. All rights reserved.