The Study Of Electriocatalytic Properties Of The Bimetallic Nanoparticle Electrocatalyst

The chemical and physical properties of nanomaterials are closely dependent on its structure,so it is effectively to improve the catalytic activity of the nanomaterials by changing the composition and structure of nanoparticles.For example,AuPd bimetal nanoparticles exhibit high electrocatalytic activity and particularly effective for the direct synthesis of hydrogen peroxide and the oxidation of alcohols.Core/shell bimetallic nanoparticles showed a great performence on electrochemical reactions due to their potentials in enhancing catalytic efficiency for energy conversions.Recently,the nanomaterials were extensively used in the electrode reaction of fuel cell and most of the reactions occurred at the condition of high temperature,it has been more and more important to study the influence of temperature on the catalytic activity.In this paper,we have studied in depth the screening of the catalysts based on SECM at normal temperature and also further detected the change of catalytic activity at a high temperature using a special thermocouple microelectrode.1.Electrocatalyst arrays with various AuPd compositions have been deposited onto an indium tin oxide(ITO)surface by an electrochemical wet-stamping(EWETS)technique.Micropatterned high-strength agarose containing different solutions of chloroauric acid and chloropalladic acid has been used to electrodeposit and generate patterns of AuPd nanoparticle arrays on ITO.The compositions of the AuPd catalysts have been determined through a combination of energy-dispersive X-ray analysis(EDX)and X-ray diffraction spectroscopy(XRD).Field-emission scanning electron microscopy(FE-SEM)and atomic force microscopy(AFM)have been employed to characterize their morphology.The electrochemical activities of the AuPd alloys for H2O2 and FcMeOH+ reduction reactions have been investigated in both redox-competition and feedback modes by means of scanning electrochemical microscopy(SECM).2.SECM approach curves,which are dependent on the substrate reaction rate,represent a very powerful tool for kinetic studies of heterogeneous reactions on AuPd array substrates.We have used SECM to characterize the charge-transfer processes occurring at the AuPd array electrodes during the reduction of ferricenium methanol,whereby the feedback current of the tip is dependent on the heterogeneous electron-transfer(HET)capability of the local area on the AuPd array.The finite element modeling method was used to simulate the tip current response as a function of the standard HET rate constant(k0)through COMSOL Multiphysics 4.3b,and the simulated probe approach curve with different values of k0 could be readily fitted to the experimental current curves.We could thereby obtain the k0 for each AuPd alloy.The results obtained from SECM images were well corroborated by calculated heterogeneous electron transfer(HET)rates for the respective AuPd electrodes,demonstrating that the SECM was applicable for the screening of multicomponent alloy catalysts and determining the optimal composition for electrocatalytic reactions.3.Core/shell bimetallic nanoparticles(Au@Pt)have been synthesized by chemical synthesis method.Field-emission scanning electron microscopy(FE-SEM)and UV-visible absorption spectrum(UV-VIS)have been employed to characterize their morphology.Core/shell nanoparticles was assembled on the surface of the thermocouple microelectrode and the electrochemical activities of the nanoparticles for oxygen reduction under the condition of heating up was investigated by cyclic voltammetry.