High-Index Faceted Cu₂O@CuO Mesocrystals Act as Efficient Catalyst for Si Hydrochlorination to Trichlorosilane

Mesocrystals (MCs) with high-index facets may have superior catalytic properties to those with low-index facets and their nanocrystal counterparts. However, synthesizing such mesocrystal materials is still very challenging because of the metastability of MCs and energetic high-index crystal facets. This work reports a successful solvothermal method followed by calcination for synthesizing copper oxide-based MCs possessing a core–shell structure (denoted as Cu₂O@CuO HIMCs). Furthermore, these MCs are predominantly bounded by the high-index facets such as {311} or {312} with a high-density of stepped atoms. When used as catalysts in Si hydrochlorination to produce trichlorosilane (TCS, the primary feedstock of high-purity crystalline Si), Cu₂O@CuO HIMCs exhibit significantly enhanced Si conversion and TCS selectivity compared to those with flat surfaces and their nanostructured counterparts. Theoretical calculations reveal that both the core–shell structure and the high-index surface contribute to the increased electron density of Cu sites in Cu₂O@CuO HIMCs, promoting the adsorption and dissociation of HCl and stabilizing the dissociated Cl* intermediate. This work provides a simple method for synthesizing high-index faceted MCs and offers a feasible strategy to enhance the catalytic performance of MCs.