A flask was charged with the photocatalyst (25 mg), aqueous ascorbic acid solution (0.1 M, 25 mL), and sealed with a septum. The resulting suspension was ultrasonicated until the photocatalyst was dispersed before degassing thoroughly by N2 bubbling for 30 minutes. The stirred reaction mixture was illuminated with a 300 W Newport Xe light source (Model: 6258, Ozone free) for the time specified at a fixed distance under atmospheric pressure. The Xe light source was cooled by water circulating through a metal jacket. Gas samples were taken with a gas-tight syringe and run on a Bruker 450-GC gas chromatograph equipped with a Molecular Sieve 13X 60-80 mesh 1.5 m × ⅛" × 2 mm ss column at 50 °C with an argon flow of 40 mL min -1 . Hydrogen was detected with a thermal conductivity detector, referencing against standard gases with known concentrations of hydrogen. Hydrogen dissolved in the reaction mixture was not measured and the pressure increase generated by the evolved hydrogen was neglected in the calculations. The rates were determined from a linear regression fit and the error is given as the standard deviation of the amount of hydrogen evolved. No hydrogen evolution was observed for aqueous ascorbic acid solutions under λ > 420 nm illumination in absence of a photocatalyst. Where stated, platinum was added to the photocatalyst by either in situ photodeposition of H2PtCl6 (8 wt. % solution in water) or pre-loaded onto samples by sonication in aqueous suspension of Pt nanoparticles followed by evaporation of water under reduced pressure.