Theoretical prediction of superatom WSi-based catalysts for CO oxidation by NO.

Catalytic conversion of NO and CO into nonharmful gases is of great significance to reduce their adverse impact on the environment. The potential of the WSi superatom to serve as a new cluster catalyst for CO oxidation by NO is examined for the first time. It is found that WSi prefers to adsorb the NO molecule rather than the CO molecule, and the charge transfer from WSi to NO results in the full activation of NO into a physically absorbed N molecule and an activated oxygen atom that is attached to an edge of the hexagonal prism structure of WSi. After the release of N, the remaining oxygen atom can oxidize one CO molecule overcoming a rate-limiting barrier of 28.19 kcal mol. By replacing the central W atom with Cr and Mo, the resulting MSi (M = Cr and Mo) superatoms exhibit catalytic performance for CO oxidation comparable to the parent WSi. In particular, the catalytic ability of WSi for CO oxidation is well maintained when it is extended into tube-like WSi ( = 2, 4, and 6) clusters with energy barriers of 25.63-29.50 kcal mol. Moreover, all these studied MSi (M = Cr, Mo, and W) and WSi ( = 2, 4, and 6) species have high structural stability and can absorb sunlight to drive the catalytic process. This study not only opens a new door for the atomically precise design of new silicon-based nanoscale catalysts for various chemical reactions but also provides useful atomic-scale insights into the size effect of such catalysts in heterogeneous catalysis.