Study On The Electrocatalytic Performance Of Gold Core@noble Metal Shell Nanowire

The nanomaterials with core-shell structure have attracted more and more attention in heterogeneous catalysis.The catalytic performance of core-shell nanomaterials is highly related to their size,morphology,composition,and interaction between core metal and shell metal,and so on.Gold（Au）substrates can serve as ideal cores for core-shell nanomaterials due to their superior electrical conductivity and chemical stability.Therefore,the design and development of Au core@noble metal shell nanomaterials with unique morphology are very important to promote the application of noble metals in electrocatalysis.In this thesis,we focus on the design and synthesis of Au core@noble metal shell nanowires and study their electrocatalytic performance in energy conversion devices such as fuel cells and water electrolysis.Due to the unique structural advantages of Au core@noble metal shell nanowires and the synergistic effects（such as interface effect,stress effect,electronic effect,and plasmon resonance effect）,a series of as-prepared Au core@noble metal shell nanowires show ehanced activity,selectivity and stability for oxygen reduction reaction（ORR）,hydrazine hydratesoxidation reaction（HeOR）,formic acid oxidation reaction（FAOR）,ethanol oxidation reaction（EOR）,and hydrogen evolution reaction（HER）,respectively.This thesis provides new ideas and directions for the development of Au-based nanocrystals and core-shell electrocatalysts.The details are as follows:（1）Preparation of Au@Ir core-shell nanowires and their electrocatalytic performance for ORR.We develop a feasible one-pot chemical-reduction strategy to rapidly synthesize high-quality Au@Ir core-shell nanowires（Au@Ir NWs）in 1-naphthol ethanol solution and explore their potential application in electrocatalysis.Experiential results show the formation of core-shell structure originates from the deposition-growth of Ir atoms at preferentially generated Au nanowires surface.Au@Ir NWs show Pt-like ORR electroactivity due to the synergism effect and structural advantages of one-dimensional nanowires.Meanwhile,Au@Ir NWs also show excellent durability and extremely enhanced methanol tolerance for ORR.（2）Preparation of polyethyleneimine（PEI）functionalized Au@Pd core-shell nanowires and their electrocatalytic performance for ORR.The PEI functionalized Au@Pd core-shell bimetallic nanowires（Au@Pd@PEI NWs）with different Pd shell thicknesses are synthesized by a chemical reduction method using Au nanowires（Au NWs）as seeds.When used as ORR electrocatalyst,Au@Pd@PEI NWs with optimal component show enhanced ORR activity and durability than commercial Pd black catalyst.Meanwhile,loose-packed PEI polymer on the Pd surface can work as barrier nanosieves to exclusively prevent the access of methanol to Pd sites,which imparts Au@Pd@PEI NWs with enhanced methanol tolerance for ORR in an alkaline solution.（3）Au@Rh core-shell nanowires are applied in hydrazine hydrate oxidation-assisted electrochemical water splitting.Bimetallic Au@Rh core-shell nanowires（Au@Rh NWs）are synthesized by simple wet chemical strategy using ultrafine Au NWs as substrate.Experimental and calculational results demonstrate that bimetallic Au@Rh NWs with optimal component reveal enhanced activity for HeOR relative to commercial Rh nanocrystals.Under light irradiation conditions,bimetallic Au@Rh NWs further show plasmon-promoted HeOR activity.The corresponding hydrazine hydrate electrolyzer realizes the anodic H₂ evolution at a voltage of only 0.18 V.（4）Au@AuPt core-shell nanowires are applied in formic acid oxidation-assisted electrochemical water splitting.Ultrafine Au core@Pt Au alloy shell nanowires（Au@Pt_xAu NWs）with different compositions were prepared by a facile one-pot precise synthesis method.Among them,Au@Pt_0.077Au NWs exhibit the best performance for FAOR and HER,which only require applied potentials of 0.29 V and-22.6 m V at 10 m A cm^-2,respectively.The corresponding formic acid electrolyzer realizes the electrochemical H₂ production at a voltage of only 0.51 V at10 m A cm^-2 current density.（5）Electrochemical performance of Au@Rh core-shell nanowires for ethanol oxidation.Au core@AuPt_0.20Rh_0.08 alloy shell nanowires(Au@AuPt_0.20Rh_0.08 NWs)with long aspect ratio and cross-linked network structure are achieved by a facile one-step synthesis.The electrochemical tests reveal that Au@AuPt_0.20Rh_0.08 NWs with the optimized composition display higher activity and stability than commercial Pt electrocatalyst and other counterparts,including higher EOR peak current density and better resistance to CO poisoning.