Photocatalytic H2 production on Pt/TiO2-SO42- with tuned surface-phase structures: enhancing activity and reducing CO formation

Photocatalytic reforming of biomass is a promising way to produce hydrogen using renewable energy. Photocatalytic reforming of methanol on Pt/TiO2-SO42- as a model reaction of biomass reforming was investigated. Sulfated TiO2 (TiO2-SO42-) with a tunable surface phase was prepared by calcining commercially available titanium dioxide TiO2 (Degussa P25) with deposited sodium sulfate Na2SO4 as a modifier. Compared with P25, the as-prepared TiO2-SO42- with Pt co-catalyst shows an increase up to 6-fold in the activity for H-2 production via photocatalytic reforming of methanol, and the CO (undesired product) concentration in the produced H-2 is decreased by about two orders of magnitude. XRD patterns and UV Raman spectra clearly indicate that TiO2 depositing with Na2SO4 can significantly retard the phase transformation from anatase to rutile during calcination at elevated temperatures. It is proposed that both the phase composition and the high crystallinity of TiO2 contribute to the high H-2 evolution activity. IR spectra of pyridine adsorption and the NH3-TPD profile show that the surface acid sites of the photocatalyst are greatly reduced after calcination at high temperatures. It is proposed that the decrease in the acidity of the samples might be responsible for the low CO selectivity.