Use of the active-phase Cu3Si alloy as superior catalyst to direct synthesis of trichlorosilane via silicon hydrochlorination.

Here we report the first synthesis of nearly pure-phase Cu 3 Si alloy that can be a highly efficient catalyst in the hydrochlorination of silicon reaction. This material was prepared by a high-temperature (1050 ​°C) calcination method in which copper and silicon powders were used as the reactants. The X-ray photoelectron spectroscopy (XPS) study revealed that the Cu and Si atoms in the Cu 3 Si alloy carried part of positive and negative charge, respectively. When employed as the catalyst in the silicon hydrochlorination to SiHCl 3 (TCS) for the production of Si polycrystals for Solar cell, the sample Cu 3 Si exhibited excellent low-temperature catalytic performance: the Si conversion and TCS selectivity respectively achieved 41.1% and 96.1% at 250 ​°C. Notably, its TCS yield at 250 ​°C was 1.2 times higher than that of the industrial catalyst-free system at 350 ​°C. Detailed analysis of the reaction process showed that the positively charged Cu atoms and negatively charged Si atoms in Cu 3 Si alloy could cleave the H–Cl bond in the reactant HCl and make the combination of H and Cl atom with Si atoms easier. Meanwhile, the reaction between the remaining Cu atom and Si was accelerated, leading to the generation of more active Cu 6.69 Si and ultimately superior catalytic performance. This work deepens the fundamental understanding of the hydrochlorination of silicon reaction, and provides an avenue for the synthesis of Si-based alloy catalysts. The use of the Cu 3 Si as a catalyst for direct synthesizing trichlorosilane with outstanding low-temperature catalytic performance; the first observation of the transformation of Cu 3 Si to the more active Cu 6.69 Si phase on the Si surface in the catalytic reaction. [Display omitted] • Nearly pure-phase Cu 3 Si alloy was synthesized via a facile high-temperature calcination method. • The Cu 3 Si alloy was used as a catalyst to study its catalytic performance in the Si hydrochlorination reaction. • The Cu 3 Si alloy exhibited excellent low-temperature catalytic performance. • The Cu 6.69 Si phase is identified as the active phase for the selective synthesis of SiHCl 3. [ABSTRACT FROM AUTHOR]