Promoting effect of In 2 O 3 on CuO for the Rochow reaction: The formation of P–N junctions at the hetero-interfaces

Here we report the first work on the synthesis of a series of xIn-CuO model catalysts for the Rochow reaction with formed P–N junctions at interfaces and with different In/Cu molar ratios. These composites were prepared by a one-pot hydrothermal method using metal nitrate salts and K2CO3 as the precursors and precipitant, respectively. Scanning electron microscopy and transmission electron microscopy characterization revealed the formation of the P–N junctions at the hetero-interfaces between CuO and In2O3, and X-ray photoelectron spectroscopy and H2 temperature-programmed reduction demonstrated a strong interaction between the CuO and In2O3 phases. The addition of In2O3 increased the electron density in the Cu nucleus, causing Cu2+ and In3+ to become less and more positively charged, respectively. When used for the Rochow reaction, the catalyst 2In–CuO (2 wt.% In on CuO) exhibited a significantly higher Si conversion and dimethyldichlorosilane ((CH3)2SiCl2, M2) selectivity than CuO, which is attributed to the formation of P–N junctions that can facilitate the charge transfer. In addition, the detailed characterizations of the fresh and spent contact masses indicated that the Rochow reaction occurred on the Si surface and probably in the areas between ultrathin two-dimensional Cu–Si species and Cu doping deposits. In2O3 species promote the outward spreading of Cu∗ (intermediate species) and improve the Cu∗ diffusion rate at the reactive interfaces. This work not only deepens the fundamental understanding of the Rochow reaction, but also provides a new approach for the design of more efficient Cu-based catalysts by adding promoters such as In2O3 and by engineering the interfaces.