Guopeng Wu

Enhancement of photocatalytic H2 evolution on CdS by loading MoS2 as Cocatalyst under visible light irradiation.

This communication presents our recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst. The MoS2/CdS catalysts show high rate of H2 evolution from photocatalytic re-forming of lactic acid under visible light irradiation. The rate of H2 evolution on CdS is increased by up to 36 times when loaded with only 0.2 wt % of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd, and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.

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 H2 production via photocatalytic reforming of methanol, and the CO (undesired product) concentration in the produced H2 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 H2 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.

Kinetics of Photogenerated Electrons Involved in Photocatalytic Reaction of Methanol on Pt/TiO2

Time-resolved IR spectroscopy was used to detect the photocatalytic reaction of methanol for H2 production on Pt/TiO2 catalysts. There exists an optimal amount of Pt loading in the Pt/TiO2 catalysts for the reaction of the photogenerated long-lived electrons. For a given amount of Pt loading, the reaction rate of the long-lived electrons on Pt/TiO2 catalysts varies greatly with the different reduction temperature of the catalysts. The possible reason is that the Pt particles occupy the surface active sites for methanol adsorption on Pt/TiO2 catalysts reduced at high temperature. This phenomenon is not observed obviously on Pt/TiO2 catalysts reduced at low temperature. The decay rate of the long-lived electrons evaluated by time-resolved IR method qualitatively correlates well with the activity of H2 production under steady-state irradiation conditions.