A Preliminary Study On Plasmon-Enhanced Photocatalysis:From Model Systems To Practical Reactions

Plasmonic effect can significantly improve the efficiency of photocatalysis by light absorption and scattering,near-fired enhancement,or "hot" electron injection.Meanwhile,it can also remarkably enhance the Raman signals,thus allowing the in-situ monitoring of surface species during catalytic reactions to uncover the fundamental insight of reaction mechanisms.Herein,nanocatalysts were assembled on the surface of shell-isolated nanoparticles(SHINs)or gold nanoparticles so that the reaction rate or the Raman signal of the nanocatalyst can be greatly enhanced by the strong electromagnetic field generated by the SHINs or Au nanoparticles.Using such a strategy,the plasmon-enhanced photocatalytic processes can be in situ studied by Raman spectroscopy,which would promote the understanding of the reaction mechanism and structure-activity relationship at a molecular levelFirst,based on the shell-isolated nanoparticles-enhanced Raman spectroscopy(SHINERS)developed by our group,we developed a new technique to achieve the in situ study of plasmon-enhanced photocatalysis by assembling nanocatalysts on of the surface of SHINs,forming a SHINERS-satellite nanocomposite.Such a strategy was employed in the in-situ study of the hydrogenation of para-nitrothiophenol(pNTP)to para-aminothiophenol(pATP).It was found that SHINs can generate strong electromagnetic field to boost the hydrogenation rate under the excitation of a visible light.Using such a strategy,effects of the size and composition of catalysts,as well as the shell thickness of SHINs,have been revealed.Furthermore,the satellite nanocomposites have also been applied to study the selective hydrogenation of cinnamaldehyde reaction.It has demonstrated that the catalytic activity under visible light irradiation can be greatly enhanced by forming PtFe-Au satellite nanocomposites,while excellent selectivity of cinnamyl alcohol is also achieved.Further studies show that,"hot" electrons generated by Au nanoparticle would transfer to the PtFe nanocatalyst thus improve the catalytic activity,while the PtFe nanocatalyst optimizes the selectivity.Meanwhile,the size of nanocatalyst in the above satellite nanocomposite was further reduced to single atomic scale by changing the coverage of the catalyst on the Au nanoparticles,leading to the formation of Au@Pd single-atom satellite catalysts.Using CO and phenyl isocyanide as the probe molecules,the surface structure of the Au@Pd was characterized by surface-enhanced Raman spectroscopy.It is found that with the decrease of the coverage,Pd would change from nanoclusters to singe atoms.In-situ SERS studies also reveal that the Au@Pd single-atom satellite catalysts show good selectivity in the hydrogenation of para-nitrophenyl acetylene and can preferentially promote the hydrogenation of C?C.