Preparation And Properties Of Pt Supported On Composite Metal Oxides Anode Catalysts For DMFC

Among the fuel cells,direct methanol fuel cells?DMFCs?are characterized by the simple structure,cheap and easy availability of methanol,friendliness of environment.However,one of the main obstacles hindering the development of DMFCs is the low catalytic activity of Pt readily poisoned by the intermediate products,generated in the methanol oxidation reaction.In order to improve the activity and stability of the Pt-base catalysts,a series of Pt catalysts supported on composite metal oxide nanofibers?NFs?were prepared and their electrocatalytic properties for methanol oxidation were systematically studied.The main contents are as follows:Part ?:Effects of doping Zn on the catalytic performance of Pt/CeO₂ towards methanol were investigated.Pt/CeO₂ and a series of Pt/CeO₂-ZnO?Pt/CZ?catalysts were prepared by electrospinning and reduction impregnation.BET,X-ray diffraction?XRD?,transmission electron microscopy?TEM?,energy disperse spectroscopy?EDS?,X-ray photoelectron spectroscopy analysis?XPS?were employed to characterize the CZ NFs and Pt/CZ catalysts.It was observed that with the increase of Zn content,the specific surface area of CZ NFs increased.When the atomic ratio of Ce/Zn was 2?CZ2?,the specific surface area was the largest.The content of Pt in Pt/CeO₂ and Pt/CZ catalysts is about 10 wt.%.However,the number-averaged diameter of Pt nanoparticles in CZ obviously less than that in pure CeO₂.XPS results showed that when Zn was doped in Pt/CeO₂,the Ce³⁺content and oxygen adsorption(O_ads)content in the catalysts increased significantly,and the binding energy of Pt?0?shifted positively?about0.50 eV?,indicating that the Pt and NFs carriers increased interaction.The catalytic performance for methanol oxidation reaction was evaluated by cyclic voltammetry?CV?,CO stripping voltammetry and chronoamperometry?CA?in acid solutions.As a result,with the increase of doped Zn,the catalytic activity of Pt/CZ was enhanced according to CV results and Pt/CZ2 had the best catalytic activity.Furthermore,compared with commercial Pt/C and Pt/CeO₂,the catalytic activity,ability to resist CO poisoning and stability of the commercial of Pt/CZ catalysts increased significantly.All results indicated that the doping of Zn was an effective method to promote the catalytic performance of Pt/CeO₂.Part ?:CeO₂-MO_x?M=Mn,Cu,Co,Zn?NFs were prepared by electrospinning,and their Pt-supported catalysts were prepared by impregnation reduction method.The crystalline,microstructure and chemical composition of Pt/CeO₂-MO_x?M=Mn,Cu,Co,Zn?were analyzed by XRD,TEM and EDS.The Pt content in the Pt/CeO₂-MO_x catalyst is 10 wt.%.Compared with Pt on CeO₂ NFs,the lattice of Pt on CeO₂-MO_x NFs shrinked,and the cell parameters and interplanar spacing became smaller.Furthermore,the Pt lattice on CeO2-CuO is distorted,indicating that the strongest interaction occurred between Pt and CeO₂-CuO NFs.The order of Pt particle size on the NFs is:CeO₂-MnO₂<CeO₂-ZnO?CeO₂-CuO<CeO₂-Co₃O₄<CeO₂.The performance of Pt/CeO₂-MO_x?M=Mn,Cu,Co,Zn?for methanol was evaluated by CV,CO stripping voltammetry and CA.It was found that all catalysts showed better catalytic performance catalysis than the Pt/CeO2 catalyst.Moreover,among the four catalysts,Pt/CeO2-CuO showed the best catalytic activity,resistance to toxicity and stability.