Morphology Control Of Tungsten Carbide Nanomaterials And Their Electrochemical Propertie

Tungsten carbide(WC)possesses a catalytic behavior,which is similar to that of platinum catalyst,and higher tolerance to CO poisoning,but its catalytic activity is much lower than that of platinum.Preparation of nano-sized tungsten carbide powder is an effective way to improve its electxocatalytic activity.In this paper,zero dimensional,one dimensional and two dimensional tungsten carbides are fabricated.The formation mechanism of the precursors for tungsten carbide preparation,and the effect of the preparing parameters on the crystal phase and morphology transformation during the preparing process are investigated,and then their electrocatalytic properties for methanol oxidation are tested,finally the correlationship between the structure and performance of tungsten carbide samples are discussed.Based on the above results and discussions,the following conclusions can be drawn:(1)Tungstic acid(H2W04)nanoplates are synthesized by a hydrothermal method,using oxalic acid as a guide agent,which is then reduced and carburized into tungsten carbide nanoplates.The experiment results show that the reaction temperature and time,and the composition of the atmosphere,in which the precursor reduced and carbonized take an important role in controlling the crystal phase and microstructure of the samples.Mesoporous WC/W2C nanoplates can be gained at 700? for 6 hours,and WC nanoplates are gotten at 750? for 6 hours,while WC nanoparticles are obtained at 850? for 6 hours.(2)Tungsten trioxide(W03)nanorods are obtained by a hydrothermal method,using sodium chloride as an additive.And W03 nanorods are then coated with carbon by a secondary hydrothermal reaction using glucose as carbon source.The composite consisted of tungsten carbide nanorods and WC/W/carbon nanotube is gained by reduction and carbonization of the above sample at 750? for 6 hours.(3)Micron-size tungsten acid iron(FeW04)spheres are prepared by a spray drying technology,using sodium tungstate and ferrous sulfate as raw materials,and citric acid as reduction agent.And then WC/Fe3W3C microspheres are gotten after reduction and carbonization at 900?.(4)The electrochemical catalytic property for methanol oxidation of the samples are investigated by a cyclic voltammetry technique.The results indicate that all the samples show a certain catalytic activity.Among them,WC/W/C nanorods exhibit the best catalytic performance,mesoporous WC/W2C nanoplates and WC nanoplates show good catalytic performance,which is better than that of tungsten carbide nanoparticles.These imply that the catalytic performance of tungsten carbide can be improved by controlling its diameter and morphology,furthermore,the preparation of tungsten carbide nanomaterials with different dimensions is one of the efficious ways to improve the electrocatalytic property of tungsten carbide.