Supported Noble Metal-based Nanocomposites And Their Applications For Electro-and Photocatalysis

Noble metal-based nanocomposites that integrate different domains to form heterogeneous structure usually exhibit enhanced physical/chemical properties,resulting in their promising applications in many fields.Specially,the nanocomposites consisting of noble metals and semiconductor have showed superior catalytic peoperties in photoelectrocatalysis.Therefore,their synthesis and application have attracted a great attention,and many important achievements have been obtained.However,the synthesis still was seriously restricted by some obstacles,such as the limitation of the low concentration for their synthesis in water phase and the large particle size in organic phase.Hence,it still is quite a challenge to develope the simple and efficient way for the synthesis of nanocomposites consisting of noble metals and semiconductora as well as the engineering of their morphology,structure and composition that would better utilize the electronic effect between them for the improvement of their catalytic properties.Based on the research idea,the detailed achievements in this thesis are listed as following:(1)A facile and efficient way for the synthesis of Ag2S-PtNCs/C has been developed.Specifically,the Ag+ precursor was firstly loaded on active carbon substrate.Subsequently,adding sulfur powder dispersed in tolune to the above system,the Ag2S nanoparticles with the mean size of about 4 nm were gained in inhibiting effect of support.Then,Pt was desposited on the surface of Ag2S nanoparticles via the simple liquid phase reducing method,and the Ag2S-PtNCs/C nanocomposites with the average of about 5 nm were ultimately obtained.Compared with those of commercial Pt/C catalyst,Ag2S-PtNCs/C nanocomposites show better specific activity and durability for the electrocatalytic oxidation of methanol due to the existed electronic coupling effect between Pt and Ag2S.(2)The above strategy was extended,and binary supported CdS-PtNCs/C and PbS-PtNCs/C nanocomposites and ternary supported Au-Ag2S-PtNCs/C nanocomposites were successfully gained.In the electrocatalytic measurement,the effluence of different sulfide semiconductors on the catalytic properties for MOR was analyzed.In addition,Au-Ag2S-PtNCs/C exhibited the highest electrocatalytic activity and stability in comparison with those of other binary and ternary nanocomposits,which should be attributed to the enhanced electronic coupling effect aroused by Au.(3)For the enhanced efficiency of oxide semiconductor TiO2 of photocatalytic water-splitting for hydrogen,bimetallic TiO2-Ag/M(M = Au.Pd,Pt)alloy nanocomposites were synthesized via GRR between Au3+,Pd2+ and Pt4+ ions 'precursors and Ag nanoparticles located the surface of TiO2,which efficiently controlled the morphology and size of bimetallic nanoparticles,and successfully tuned the compound interface between noble metal and semiconductor TiO2 and compositon of noble metal on the surface of TiO2.Because of the existence of Au,TiO2-Ag/Au not only showed stronger plasma resonance absorption,but also exhibited 3.3 times higher efficiency of photocatalytic water-splitting for hydrogen,compared with those of TiO2-Ag nanocomposites.In addition,alloying Ag on the surface of TiO2with Pd and Pt,the schottky barrier was formed in the compound interface between TiO2 and noble metal,which enhanced the dissociation of photogenerated electron hole pair in TiO2,thus resulting in the improvements of their efficiency of the photocatalytic water-splitting for hydrogen.