Theoretical prediction of superatom WSi12-based catalysts for CO oxidation by N2O

Abstract

Catalytic conversion of N₂O and CO into nonharmful gases is of great significance to reduce their adverse impact on the environment. The potential of the WSi₁₂ superatom to serve as a new cluster catalyst for CO oxidation by N₂O is examined for the first time. It is found that WSi₁₂ prefers to adsorb the N₂O molecule rather than the CO molecule, and the charge transfer from WSi₁₂ to N₂O results in the full activation of N₂O into a physically absorbed N₂ molecule and an activated oxygen atom that is attached to an edge of the hexagonal prism structure of WSi₁₂. After the release of N₂, the remaining oxygen atom can oxidize one CO molecule via overcoming a rate-limiting barrier of 28.19 kcal mol⁻¹. By replacing the central W atom with Cr and Mo, the resulting MSi₁₂ (M = Cr and Mo) superatoms exhibit catalytic performance for CO oxidation comparable to the parent WSi₁₂. In particular, the catalytic ability of WSi₁₂ for CO oxidation is well maintained when it is extended into tube-like W_nSi_6(n+1) (n = 2, 4, and 6) clusters with energy barriers of 25.63–29.50 kcal mol⁻¹. Moreover, all these studied MSi₁₂ (M = Cr, Mo, and W) and W_nSi_6(n+1) (n = 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.