Silicon‐Doped Graphene as a Catalyst for Hydrogenation of Carbon Dioxide: A Molecular Simulation Study

Abstract

AbstractThe catalytic effect of Si‐doped graphene nanoflakes (NFs) on CO2 reduction with molecular hydrogen was explored theoretically at the TPSS/def2‐SVP+D3BJ level of theory. Substituting carbon with silicon generates defects in the NF structure, which leads to a polyradical ground state of the NF. The silicon defect enhances the reactivity towards the substrates. Si‐doped graphene NFs exhibit higher catalytic activity for CO2 reduction to formic acid than silicene. Notably, Si‐doped graphene favors formic acid over carbon monoxide, which is similar to silicene. Formic acid to formaldehyde and formaldehyde to methanol conversions have also been studied, sometimes showing improved efficacy of Si‐doped graphene over silicene. The final reduction step, the methanol to methane reaction, occurs in four steps, with the rate‐determining step involving hydrogen transfer from silicon to methyl, whose activation energy is lower than that of silicene. Si‐doped graphene NFs act as better catalysts with lower activation energies than those of silicene. Overall, silicon‐doped graphene enhanced the catalytic activity while maintaining the environmental stability of the graphene.