Preparation Of Carbon Nanotubes Supported Pd-based Nanocatalysts And Their Performance For Ethanol Or Formic Acid Electrooxidation

Fuel cell is an ’electrochemical’ device that can convert the chemical energy of a fuel(e.g.,hydrogen,ethanol,formic acid,etc.)and an oxidant(oxygen or air)into electricity,heat and water in the presence of the catalysts.Among various fuel cells,the proton exchange membrane fuel cell(PEMFC)has been used in transportation and portable electronic devices due to its advantages of low operation temperature,quick start,high efficiency in energy conversion and convenience of storage.Up to date,Pt-based nanomaterials are commonly used for the anode catalysts of PEMFC.However,some disadvantages of Pt catalysts significantly hinder their extensive application,such as high cost,limited resource and easy poisoning by COads intermediates.Therefore,reducing the amount of precious metals,seeking cheap nanomaterials and improving the electrochemical performance of catalysts have become the research hotspots.Palladium is much cheaper and abundant in nature than platinum.Considering the practical application of fuel cells,the palladium is expected to become an alternative to platinum.However,the palladium catalysts also face with the similar problems to platinum(e.g.,easy poisoning and low stability).In this thesis,on the basis of the active ingredient of Pd,the second metal was introduced to form the Pd-based nanocomposite catalyst,which can obviously improve the surface element composition,adequately use the synergistic effect of two metallic elements,and thus drastically enhance the electrochemical performance and anti-poisoning ability of the catalysts.The original results are as follows:(1)The core-shell structured Ru@Pd/multi-walled carbon nanotubes(MWCNTs)catalyst was prepared via a simple two-step chemical reduction process and its electrocatalytic performances for ethanol and formic acid oxidation were investigated.Through the physical characterizations of X-ray diffraction(XRD),transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS)as well as the electrocatalytic performance tests,it is found that the Ru@Pd nanoparticles with a smaller particle size of 2.3 nm are uniformly distributed on the surface of MWCNTs,and they exhibit excellent electrocatalytic performance for ethanol and formic acid oxidation.(2)With MWCNTs as the support,the MWCNTs supported PdCd alloy nanocatalyst was synthesized by one-step hydrothermal method,and its electrocatalytic performance for ethanol oxidation was investigated.The as-prepared nanomaterials were characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDX),X-ray photoelectron spectroscopy(XPS)and electrochemical tests.The results show that the as-prepared PdCd/MWCNTs catalyst exhibits higher electrocatalytic activity,stability and CO-tolerance ability for ethanol oxidation.(3)With the choline chloride/ethylene glycol deep eutectic solvent as the medium,the MWCNTs supported Pd-CeO2 nanocatalyst(Pd-CeO2/MWCNTs)was prepared via a one-step solvothermal method.The crystal structure,morphology,size and electron interaction of as-prepared catalysts were characterized by XRD,TEM,XPS and EDX.The electrochemical tests of cyclic voltammetry,chronoamperometry and CO stripping voltammetry show that the Pd-CeO2/MWCNTs catalyst could significantly enhance the electrocatalytic performance for formic acid oxidation.