Preparation Of Morphology Controllable Tungsten Carbide Composites And Its Electrocatalytical Performance

Due to its excellent thermal and electrochemical stability,platinum-like catalytic behavior and resistance to CO poisoning,tungsten carbide（WC）is regarded as an ideal candidate catalyst for direct methanol fuel cells（DMFCs）.However,because of its limited synthesis method,WC generally has big size,low specific surface area and poor conductivity which hinder the real application in DMFCs.The morphology control is proved to be an effective approach to adjust the chemical and physical properties.Nowadays,there are very limited researches on the synthesis of tungsten carbide with controlling specific structures.Related studies successfully synthesized nanoplates,nanorods of tungsten carbides.Except the morphology control,appropriate supports can also increase the active sites to enhance electrocatalytic performance of WC.Efforts have been focused on finding suitable supports such as carbon nanotubes to disperse WC.However,tungsten carbide can hardly decorated on the nature carbon nanotubes due to its chemically inert basal planes.The usual way to load WC on the carbon nanotubes is to add the function groups on the carbon nanotubes for the following synthetic process via a harsh oxidative pretreatment.The whole process is too complex and loading of WC is restricted by the amount of function groups.In this paper,we introduced a novel protocol to efficiently synthesize tungsten carbide nanomaterials with pure crystal structure and certain specific morphology.In which,W₁₈O₄₉ with surface oxygen vacancies and special morphology is chosen as the precursor.The existence of large quantities of oxygen vacancies give plenty channels for diffusion and keep the specific morphology of WC in the carbonization process.In addition,by use of an elegant structure design,we also developed an in-situ preparation method which is facile and clean to obtain WC/CNTs composites with special constructions such as fuzzy ball and network structure.The main research can be summarized as follows:（1）In this section,we prepared W₁₈O₄₉ nano materials in a microwave assistant method.And we try to establish the oxygen vacancy controlled mechanism to explain the reason why different morphologies of W₁₈O₄₉ can be prepared.Hydrogen peroxide and oxygen are chosen as oxidants to investigate their function during the preparation of W₁₈O₄₉.（2）By utilization of the oxygen vacancies and specific morphologies of W₁₈O₄₉,we successfully prepared tungsten carbide（WC）nanomaterials with pure crystal structure and certain specific morphology,such as nanorods,sea unchin like,microspheres and nanosheets.The effect of oxygen vacancies is also discussed.After loading with platinum nanoparticles,Pt/WC with specific morphology showed an excellent electro catalytic performance.（3）With the elegant structure design,we in-situ prepared the fuzzy ball and network like WC/CNTs composites which are the supports to acquire Pt-WC/CNTs.It was found that Pt-WC/CNTs with network structure showed the better electrochemical activity and stability in methanol oxidation.