Chemical Reduction Preparation In Deep Euteceic Solvents Of Pd And Pt-based Catalysts And Their Applications In Fuel Cell Electrocatalysis

A fuel cell is an ’electrochemical’ device that converts the chemical energy of a fuel(e.g.,hydrogen,methanol,formic acid etc.)and an oxidant(air or pure oxygen)in the presence of a catalyst into electricity,heat and water.Among various fuel cells,the proton exchange membrane fuel cell(PEMFC)has been used in portable electronic devices(e.g.,mobile communications and computers)due to its advantages such as low operation temperature,quick start,high efficiency in energy conversion and convenience of storage and transportation.Noble metals of Pt and Pd have been used as the most effective PEMFC catalysts owing to their several advantages of higher catalytic activity,chemical stability,exchange current density and free energy.However,some disadvantages of noble metal catalysts,such as high cost,limited resource and easy poisoning by COads,significantly hinder their commercial application.Therefore,it is urgent to explore new anode catalysts to reduce the amount of noble metal and improve the performance of catalysts.Recently,the preparation in deep eutectic solvent(DESs)of electrocatalytic materials for fuel cells has attracted intensive interests.However,several electrocatalysts reported in literatures have been synthesized by the electrochemical method in DESs,studies on preparation of fuel cell catalysts in DESs by chemical reduction method have not yet been reported.In this thesis,two novel electrocatalysts have been fabricated in DESs,and their electrocatalytic performances for formic acid and methanol oxidation have been investigated,respectively.The original results are as follows:(1)With the choline chloride/urea DESs as the medium,a novel flower-like palladium nanonetwork structure(Pd FNNs)was successfully synthesized by chemical reduction method,and its electrocatalytic performance for formic acid oxidation was investigated.The prepared materials were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive X-ray spectroscopy(EDX)and X-ray photoelectron spectroscopy(XPS)and electrochemical tests.The results show that the Pd FNNs could significantly enhance the electrocatalytic performance for formic acid oxidation.(2)With the choline chloride/ethylene glycol DESs as the medium,multi-walled carbon nanotubes(MWCNTs)-supported PtV alloy nanocatalyst(PtV/MWCNTs)was successfully prepared via a one-step solvothermal method.The crystal structure,morphology,size and electron interaction of as-prepared catalysts were characterized by XRD,TEM and XPS.Their electrocatalytic performances for methanol oxidation were investigated by cyclic voltammetry,chronoamperometry and CO stripping voltammetry methods.The results demonstrate that the prepared PtV/MWCNTs catalyst exhibits higher electrocatalytic activity,stability and CO tolerance ability for methanol oxidation.This study is of significance for the design and synthesis in non-aqueous system of Pt-base and Pd-base catalysts with high performance.The as-prepared catalysts show a potential prospect in direct fuel cells and other electrocatalytical fields.