| Hydrogen as a clean and pollution-free energy carrier with high energy density has been drawn to wide attention.However,it is still an urgent problem how to efficiently and quickly produce a large amount of hydrogen.Some methods have been developed,including electrocatalytic water splitting,photocatalytic water splitting,and biomass hydrogen production.Among them,photocatalytic hydrogen production has become one of the hot spots in the hydrogen energy field since it can convert the inexhaustible sunlight into chemical energy with the assistance of semiconductor photocatalysts.It is significant in saving energy and relieving environmental pollution.Nevertheless,the photocatalytic performances of semiconductor photocatalysts still need to be further promoted due to the narrow spectral response range,easy recombination between carriers,and insufficient redox ability.In this thesis,three metal cluster supported photocatalysts were successfully prepared,including Pt cluster supported CdS,Pt cluster supported TiO2 and Au nanoparticles modified Pt cluster/CdS photocatalyst.Compared with new semiconductor photocatalysts,the ones mentioned above obviously improved photocatalytic performances.The related contents are summarized as follows:1.The Pt5/CdS photocatalyst with excellent visible light catalytic performances was successfully synthesized through dispersing atomically precise Pt clusters on multi-armed CdS nanorods.The X-ray absorption fine spectroscopy(XAFS)analysis showed that monodisperse active sites were formed on the surfaces of CdS nanorods.Ultra-fast transient absorption(TA)studies showed that the introduction of Pt clusters opened a new electron transfer channel for the photogenerated electrons generated on CdS nanorods.DFT calculation confirmed that the successful loading of Pt atoms on the surfaces of CdS nanorods introduced new active sites and improved the intrinsic activity of the CdS photocatalyst.Compared with the new CdS photocatalyst,the prepared Pt5/CdS photocatalyst has great advantages in kinetics and thermodynamics.2.Similarly,Pt5/TiO2 photocatalyst was successfully obtained by loading the atomically precise Pt clusters on the surface of TiO2.The photocatalytic performance tests showed that under the radiation of the simulated sunlight,the photocatalytic hydrogen evolution rate of the as-prepared Pt5/TiO2 photocatalyst reached 35710 μmol h-1 g-1,which was about 280 times higher than the 129 μmol h-1 g-1 of a single TiO2 catalyst,and also exceeded most of the Pt-based photocatalysts reported so far.Electrochemical impedance spectroscopy and photocurrent response measurements showed that Pt5/TiO2 photocatalyst had lower charge transfer resistance and higher carrier separation efficiency.In addition,commercial-grade TiO2 was used to synthesize Pt5/TiO2 photocatalyst,so the current approach was costeffective.3.A multi-step wet chemical method was designed to successfully obtain Au nanoparticles modified atomically precise Pt clusters/CdS photocatalysts.The photocatalytic water splitting tests showed that the as-obtained composite photocatalyst’s hydrogen evolution rate was twice as high as the Pt cluster/CdS photocatalyst.Ultrafast spectroscopy studies revealed that during the photocatalytic process,the semiconductor photocatalyst could accept many hot-electrons generated by the local surface plasmon resonance(LSPR)effect of Au nanoparticles within a short time.Subsequently,these hot electrons were transferred through the fast transfer channel constructed by Pt clusters and finally participated in the surface redox reaction to the maximum extent.As a result,the photocatalytic performance of the photocatalyst was significantly improved.The above facts verified that a specific synergistic relationship between metal clusters and the LSPR effect should exist. |
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