Synthesis Of Tantalum-Based Composite Catalysts And Study For Electrocatalytic Performance Toward Methanol And Ethanol Oxidation

In recent years,the large consumption of fossil fuels has been cause the serious environmental pollution and global warming.The fossil resources are non-renewable and they are becoming scarcer because of the consumption.Direct alcohol fuel cells?DAFCs?can convert chemical energy into electrical energy directly by electrochemical oxidation.The intermediate and final products of alcohols oxidation have less environmental pollution.In addition,the conversion efficiency is not being limited by Carnot cycle.It is significant to solve the energy problems.At present,the commercializations of DAFCS face the following problems:First,Pt or Pt-based materials are used mostly in the alcohol oxidation electrode materials.The production costs are high because of the lack of Pt resources and expensive.Second,Pt-based catalysts are easily absorbed the intermediate products?such as CO,etc.?of alcohols oxidation,and their electrochemical properties decreases rapidly.In this work,a series of Ta-based catalysts with modification were synethesized.Au nanoparticles loaded on tantalum oxide nanorods?Au/Ta₂O₅Ns?,Au/Ta₂O₅Ns composited with graphene?Au/Ta₂O₅Ns-rGO?,and the adsorption of Ta⁵⁺on carbon spheres and the loading of Au nanoparticles?Au/C?Ta??to improve electrocatalytic activity of methanol and ethanol.The research contains mainly the following aspects:?1?The preparation of Au/Ta₂O₅Ns with different Au loading amount by reflux method.The crystal phase and morphology of the samples obtained were characterized with X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,and X-ray photoelectron spectroscopy?XPS?techniques.The electrons transfer and microstructure of Ta₂O₅after Au loading are discussed using density functional theory?DFT?calculation.The results show that the electrons transfer is enhanced,and improved the electrocatalytic activity of Au/Ta₂O₅Ns.The electrocatalytic activity,stablibility,and resistance of samples are investigated by cyclic voltammetry?CV?,chronoamperometry?I-t?and electrochemical impedance spectroscopy?EIS?techniques.The results show that the catalyst exhibited excellent electrocatalytic activity for the methanol and ethanol oxidation in acidic and alkaline media.?2?Based on the study of Au/Ta₂O₅Ns,the Au/Ta₂O₅Ns with graphene composite catalyst?Au/Ta₂O₅Ns-rGO?was synthesized by the reflux method.The Au/Ta₂O₅Ns-rGO catalysts were characterized using XRD,SEM,TEM,XPS and BET techniques.The XRD and XPS results show that the crystal phase and Au valence state of Au/Ta₂O₅Ns had not change after rGO composite.The SEM and TEM results show that the rGO and Au/Ta₂O₅Ns formed prefect composite.The EIS and BET results show that the conductivity enhanced,specific surface area enlarged,and the active sites changed more of Au/Ta₂O₅Ns-rGO after rGO adding.The electrochemical measurements results show that the catalyst had excellent electrocatalytic activity toward the methanol and ethanol oxidation in acidic and alkaline media.The stability and CO tolerance of the Au/Ta₂O₅Ns-rGO were improved.?3?The carbon spheres were synthesized by hydrothermal method,then Ta⁵⁺was adsorbed by adsorption.The Au nanoparticles were loaded on the surface of samples,and the different ratio to Au and C catalysts?Au/C?Ta??were obtained.The crystal phase and morphology of the samples obtained with XRD,SEM,TEM and XPS techniques.The electrocatalytic performance for methanol and ethanol oxidation were measured using CV,I-t and EIS techniques in acidic and alkaline media.The results show that the Au/C?Ta?had high electrocatalytic activity,low resistant,strong CO tolerance,and good stability.