A computational study of the competing reaction mechanisms of the photo-catalytic reduction of CO on anatase(101).

We perform a computational study of three different reaction mechanisms for the photo-catalytic reduction of CO on the TiO anatase(101) surface known as (i) the carbene, (ii) the formaldehyde and (iii) the glyoxal pathways. We define a set of approximations that allows testing a number of mechanistic hypotheses and design experiments to validate them. We find that the energetically most favourable reaction mechanism among those proposed in the literature is the formaldehyde path, and the rate-limiting step is likely to be the formation of CH radicals from dissociation of CHOH. We show that an intermediate that supports this mechanism is OCHOH. We also find that formaldehyde would be an energetically favorable intermediate forming from CO and HCO, intermediates that are proposed in the early stage of the carbene and glyoxal pathways respectively. Some possible variants of mechanisms and methods to ease the formation of CH radicals are also discussed.