Synthesis of metal silicides using polyhedral oligomeric silsesquioxane as a silicon source for semi-hydrogenation of phenylacetylene

Abstract

Metal silicides as new typical intermetallic compounds have great potential in catalytic reactions. Here, an efficient route for synthesizing metal silicides (such as Pd₂Si, Ru_xSi, Pt_xSi and Ni₂Si) is proposed using polyhedral oligomeric silsesquioxane as a silicon source under a H₂ atmosphere. TG, FT-IR, Raman and XPS characterization methods were performed to investigate the formation mechanism, which indicates that the Si–C bonds from phenyl-POSS decomposition benefit the formation of a silicide phase under a H₂ atmosphere at a high temperature (1000 °C). Compared with Pd/SiO₂, a Pd₂Si/SiO₂-HT catalyst with post-treatment showed 97% conversion and 86% selectivity towards styrene in the semi-hydrogenation of phenylacetylene. The DFT theory also demonstrated the moderate adsorption of styrene (−0.62 eV) and a high energy barrier for deep hydrogenation (−1.01 eV) on a Pd₂Si (111) surface compared to those on Pd (−0.73 eV), which can explain the high selectivity of styrene on Pd₂Si.