Impact of oxygen vacancy in CuO-ZnO catalysts on the selectivity of dimethyldichlorosilane monomer in the Rochow reaction

In metal oxides, oxygen vacancies (OV) are ubiquitous and intrinsic defects that can pronouncedly impact the physicochemical properties of the catalysts. In this work, we investigated the effect of the OV concentration in CuO-based catalysts on the performance of the Rochow reaction. A series of foamed CuO-ZnO composite catalysts with a highly porous structure were synthesized by a facile co-precipitation method, followed by hydrogen reduction at different times. When used in the Rochow reaction to synthesize dimethyldichlorosilane (M2), the CuO-ZnO-20 catalyst with an appropriate OV concentration exhibited the highest M2 selectivity at a similar Si conversion level of the other CuO-ZnO catalysts with different OV concentrations. By correlating the structure and performance of the catalysts, we found that the OV at an appropriate concentration in CuO-ZnO-20 acted as the adsorption sites for the reactant CH3Cl molecules, and generated an optimized electronic structure for surface CuO as confirmed by the X-ray photoelectron spectroscopy analysis (XPS), thereby optimizing the adsorption strength of CH3Cl and ultimately promoting the formation of alloyed CuxSi active phase. This work provides an effective strategy for designing heterogeneous catalysts with high selectivity by controlling the OV concentration in the catalysts.