(A) Reaction mechanism for the CO dissociation into C + O. (B) Reaction mechanism for the HCO dissociation into HC + O. (C) Reaction mechanism for the H₂CO dissociation into H₂C and O. (D) Reaction mechanism for the first oxygen hydrogenation to OH. (E) Reaction mechanism for the second oxygen hydrogenation to H₂O. (F) ZPE-corrected PESs (in kcal mol^–1) for the different proposed CO dissociation mechanisms, as well as of H₂O and CH₃OH formation, using as the 0th reference energy the Fe⁰@SiO₂ + H₂ + CO asymptote. The optimized geometries of the five transition state structures involved in the three different C-O dissociations and in the H₂O formation are also shown (bond distances in Å). The asterisk symbol (*) denotes from which atom the relevant molecule is coordinated with Fe. Color-coding: H atoms are represented in white, C atoms in gray, O atoms in red, Si atoms in beige, and Fe atoms in orange.