Construction And Properties Of Pt - Based Photocatalyst Supported On Molybdenum Compounds And Carbon Composite Carrier

Direct methanol fuel cell（DMFC） is considered as one of the promising energy conversion device for portable electronic equipment and electric vehicle. This is because it uses methanol as fuel and has low cost, high energy density, renewable and easy storage and transportation. However, some challenges still need to be overcome for the anode Pt-based catalyst of DMFC, such as the high cost, CO poisoning and support corrosion. All the factors restrict the large-scale commercialization of DMFC.Therefore, mixing molybdenum compounds with Vulcan XC-72 carbon black as hybrid support into the DMFC anode catalyst can effectively improve the above problems, it still can not reach the performance requirements of commercialization. In this regard, MoO₃ nanorods, CeO₂-MoO₃ composite nanorods and MoS₂ nanoparticles were prepared in this work to expect to improve the performance of MoO₃, and electrochemical oxidation performance of methanol were also studied for these three kinds of molybdenum-based compounds are mixed with Vulcan XC-72 carbon black.（1） MoO₃ nanorods were prepared by a simple hydrothermal method. In order to determine the suitable reaction conditions of preparing MoO₃ nanorods,the influences of the hydrothermal reaction temperature and time on the morphology were studied.Based on the study, the suitable reaction conditions to prepare MoO₃ nanorods were regarded as hydrothermal reaction at 180 °C for 24 h. The prepared MoO₃ nanorods was very smooth and clean on the surface with the length of 6 μm and the width of 250 nm. The results of electrochemical tests showed that the current density of methanol electrochemical oxidation of Pt/MoO₃nanorod–C catalyst is 442 m A mg–1,the catalyst shows good resistance to CO poisoning and electrochemical stability.（2） In order to further enhance the co-catalytic effect of MoO₃ nanorod onmethanol electrooxidation, the CeO₂-MoO₃ composite nanorods with different Ce:Mo molar ratio were prepared in this work. The results of SEM show that the as-prepared composite oxides are unique nanorods with rough and unclear surface and the length and width of nanorods are about 2 μm and 330 nm, respectively. The results of Raman and XPS indicate that the incorporation of Ce element enhance the oxygen vacancy and deficiency of MoO₃, thereby further improving the co-catalysis effect. The composite nanorods were then mixed with Vulcan XC-72 carbon black used as support for Pt catalysts. The influences of Ce:Mo molar ratio on the performance of CeO₂-MoO₃ composite oxides for methanol electrooxidation were studied. The results showed that when Ce:Mo molar ratio is 0.20:0.80, the as-prepared catalyst exhibits that the best activity of methanol electrooxidation, which current desity up to 585 m A mg–1.Furthermore, the catalyst also exhibits a good resistance to CO poisoning and electrochemical stability.（3） MoS₂ nanomaterials were prepared by a hydrothermal method. In the process of preparation, ammonium heptamolybdenum tetrahydrate was used as molybdenum source, thioureaas areducing agent, deionized water as a solvent to prepare MoS₂.Subsequently, the as-prepared MoS₂ were mixed with Vulcan XC-72 carbon black used as support for Pt catalysts. On the basis of our previous research, Pt/CeO₂-Cu O–C catalyst was also prepared in this article. The methanol oxidation performance of two catalysts were studied. The results show that both catalysts showed enhanced activity of methanol electrooxidation, and high CO poisoning resistance and stability. While,the improvement of methanol oxidation performance for Pt/MoS₂–C catalyst was significantly. Presumably due to itself special properties and structure. For example,MoS₂ has the stable physical and chemical properties as well as similar to the structure of graphene, which make it show the highly anisotropic. Thus, MoS₂ shows excellent electrochemical propertiescompared to oxide nanomaterials.