There is growing interest in the reforming of methanol and other bio-oxygenates as highdensity, CO 2 -neutral, renewable sources of H 2 . Photocatalysis is worthy of investigation as a potentially economic means to drive such endothermic processes. In this study, in-situ DRIFTS, adapted for optical pumping and coupled to on-line MS, was used to observe the surface of TiO 2 (Degussa P25) during photo-metallization from pre-sorbed hexachloroplatinate, at a nominal Pt loading of 1 wt%, and to evaluate photo-reforming of methanol over the resulting Pt/TiO 2 composite. The irreversible growth of a quasi-continuum absorption, characteristic of the surface plasmon resonance of zerovalent Pt nanoparticles, along with bands at 2050 and 1830 cm -1 typical of metal-adsorbed CO, indicated that photometallization was complete typically within 2 hours. Methanol reforming was photocatalyzed at room temperature but in low quantum efficiency, ø ≈ 0.01. However, this was raised substantially, to ø ≈ 0.07, simply by the application of mild heating (T ≤ 70 ºC). Photoreforming proceeded at a fixed rate but the H 2 /CO 2 ratio generally exceeded that of the reforming stoichiometry, suggesting some retention of CO 2 . The photo-thermal synergy was rationalized by model DRIFTS studies, starting from formalin (hydrated formaldehyde), which revealed key features of the mechanism. TiO 2 promoted the Cannizzaro disproportionation in the dark, yielding formate and methoxy species already at 40 ºC. While methoxy was effectively cycled back to the initial photo-dehydrogenation stage, the slow step was identified as formate decomposition to H 2 and CO 2 . The low value measured for the apparent activation energy (~40 kJ mol -1 ) was taken as supporting evidence for 'waterassisted destabilization' of formate, as originally reported by Shido and Iwasawa. No evidence was found for an alternative thermal or photo-reforming mechanism involving the Pt-CO ad species.

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