Preparation And Electrochemical Performance Of Tungsten Carbide/Reduced Graphene Oxide Based Composites

Fuel cell(FC),a kind of green energy technology,including direct methanol fuel cell(DMFC)and direct formic acid fuel cell(DFAFC)has been well studied because of its high energy efficiency,low operating temperature,the advantages of simple structure,clean production.However,the two types of fuel cell are facing some major problems,such as low catalytic activity,poor stability,easy to poisoning,high price,so the development of catalyst preparation technology,the preparation of highly active and stable catalyst,the improvement of utilization ratio and the decrease of Pt dosage,are the effective ways to solve the problems of DMFC or DFAFC.In recent years,reduced graphene oxide(RGO),as an ideal carrier of catalysts has been widely reported.It has been playing an important role in terms of efficient loading and utilization of active ingredients,such as tungsten carbide(WC),Pt and Pd.At the same time,WC,as a catalyst in the application of direct liquid fuel cell(DMFC and DFAFC),has quite a few reports.WC,which has good corrosion and oxidation resistance,platinum features and poisoning resistance,is an ideal catalyst or promoter.In this paper,we first prepared graphene oxide(GO),then WC/RGO composites were prepared using the graphene oxide as the initial support,and then binary and ternary anode catalysts with low-loading precious metals were prepared using the WC/RGO composites as a support.Finally,the electrochemistry activities toward methanol oxidation reaction(MOR)or formic acid oxidation reaction(FAOR)of the anode catalysts were investigated.The main research work can be summarized as follows:(1)Firstly,graphite oxide(GO-i)was prepared by modified Hunmmers method.Then RGO was prepared on the basis of GO-i through rapid heat treatment in muffle furnace and hydrogen reduction at low temperature,which is simple and solvent-free,providing a choice of large scale preparation of RGO.XPS results show that the C/O ratio is up to 18.6,indicating that this method for preparing RGO has lower residual oxygen.N2 adsorption and desorption tests show that RGO layers have high specific surface area and large spacing.Moreover,heat treatment toward GO-i in muffle furnace to prepare GO provides a train of thought in preparation of WC/RGO composits.(2)At the beginning,GO with high surface area was prepared by microwave irradiation toward GO-i.Then WC/RGO(IL),which used the GO as the earrier,was prepared with the assistant dispersion of WCl6(the precursor of WC)in ionic liquid[BMIM][PF6])by impregnation and reduction-carburization technique.For comparison,RGO without loading WC obtained by direct carbonization and WC/RGO synthesized in the absence of ionic liquid were also prepared,denoted as RGO and WC/RGO,respectively.The results show that ionic liquid plays a role in dispersion in the preparation of WC/RGO composite,which gave better performance in nitrobenzene electroreduction.However,removing of ion liquid caused the lost of a certain amount of tungsten groups and reduced the WC actual content,which was not benificial to the loading of precious metal particles in the subsequent chapters.(3)GO was prepared with three methods(heat treatment toward GO-i by muffle furnace and microwave irradiation,and chemical processing toward GO-i by PDDA),and WC/RGO composite supports were prepared refer to the previous chapter.Then different Pt-WC/RGO composite,namely Pt-WC/RGO,Pt-WC/RGO-D?Pt-WC/RGO-P and Pt-WC/RGO-W,were prepared using the different WC/RGO composite supports and their electrochemistry performances were also compared.The results indicate that proper treatment(microwave irradiation)toward GO-i not only increase gently the interlayer spacing of GO,but also retain the anchor role of oxygen-containing functional groups to ensure the small size and relatively good dispersion of Pt.Pt-WC/RGO-W shows better performance toward MOR than Pt-WC/CNTs-W,indicating that RGO is better than CNTs when used as a support.Compared with Pt/C(JM)and PtRu/C(JM),Pt-WC/RGO-W still has the best catalytic performance,which is related to the small size and uniform dispersion of WC and Pt,but also comes from excellent synergistic effect between WC and Pt.(4)GO alcoholic suspension was prepared by ultrasonication treatment toward GO-i and a series of Pd-WC/RGO composites with different WC mass percentage were prepared using a similar method mentioned in the previous chapter.The electrochemistry measurement results indicate that WC can increase the electrocatalytic activity,especially the 25%WC content,which is resulted from the best synergistic effect between 25%WC and Pd.Pd-WC(25)/RGO shows better performance toward MOR than Pd-WC(25)/RGO(SB),indicating that microwave ethylene glycol reduction method is better than common chemical reduction.(5)GO water suspension was prepared by ultrasonication treatment toward GO-i,and Pt-WC/RGO,PtRu-WC/RGO and PtPd-WC/RGO composites were prepared using a similar method mentioned in the previous chapto.Compared with Pt-WC/RGO,PtM-WC/RGO composites show better performance,indicating that the addition of the third component M will improve the catalytic activity which,results from the extra bifunctional mechanism between Pt and M.