Application Of Tungsten Carbide Based Composite Materials In Electrocatalysis And Cemented Carbide

China has rich tungsten resources,tungsten reserves for the world's total reserves first.Relatively speaking,the reserves of other rare metals in China are not sufficient,and the industrial needs are very dependent on imports from abroad,which seriously hinders the development of relevant industrial industries in China.Therefore,if we can make full use of China's rich tungsten resources to make up for or replace the shortage of precious metals,or fully improve the production technology and utilization efficiency of China's tungsten resources in the traditional industries,it will have a greater role in promoting the construction of China's national economy.Tungsten carbide(WC)has the properties of platinum(Pt)because of its unique hybrid orbital,which can partially replace the precious metal Pt catalyst,and is often used in the field of electrocatalysis.In addition,WC is often used in cemented carbides because of its high hardness.However,because of its brittleness,transition metals(Fe,Co,Ni,etc.)with high yield strength and good wettability with WC are needed as the bonding phase.Therefore,the preparation of nano WC matrix composites and their related applications are of great significance.WC precursors were prepared by hydrothermal template method.Based on the process of preparing WC in laboratory,the precursors were carbonized to obtain carbon-coated tungsten carbide(WC@C)powder,and Pt was deposited on the nanocrystalline particles by microwave.A flower cluster(200-500 nm in size)precursor composed of relatively dispersed small nanosheets(10-20 nm)was obtained.Citric acid(C₆H₈O₇·H₂O)was used as the precursor shape and size regulator,and graphene oxide(GO)was used as a dispersant.The morphology and size of H₂WO₄ are related to the distribution state of GO in the reaction system.The tungsten oxide(WO₃)obtained by heat treatment has a uniformly distributed monolithic lamellar structure with a thickness of about 10 nm and a diameter of about 100 nm.A core-shell WC@C composite was prepared by using small molecule mixed alcohols as carbon source,which was composed of lamellar WC and graphitized carbon layer.The lamellar thickness is about 10-50nm,and the length and width are about 0.5-1?m.The results of hydrogen evolution reaction show that the catalyst(5%Pt-WC@C)performs better than 10%Pt-WC@C and 1%Pt-WC@C in acidic solution.The optimal current density of 10 m A cm^-1 corresponding to the overpotential is 87.6 m V,and the Taefell slope is 51.59 m V decade^-1.It is close to the catalytic performance of 20%Pt-C commercial catalyst,which proves that the composite catalyst synthesized by this method is feasible for the synthesis of low Pt catalyst.In view of the traditional method the required equipment and technological process of complicated,energy consumption,process control is relatively difficult,it's easy to have a set of composite powder preparation yuan uneven distribution,grain size distribution and morphology control,performance is not stable,choose soluble salt tungsten,cobalt salt,organic carbon source as key raw materials,such as through the liquid molecular hybrid tungsten carbide-cobalt(WC-Co)precursor,effective control of size of WC-Co precursor form.The particle size of WO₂and Co O₂,the main transition intermediates of the morphology and size change of WC-Co composite powder,is uniform,and the average size is less than 100 nm.The nanoscale intermediate products provide a guarantee for the nanocrystallization of the carbonized WC-Co powder.The average particle size of the final sample is 150 nm.The elements C?W and Co are evenly distributed,and the sample maintains pure WC phase and Co phase.The results of carbon content test showed that the total carbon content of the composite powder was about 5.63%,and the free carbon content was 0.08%,which was in line with the standard range of carbon content of WC-8Co(YG8).After SPS sintering process exploration,the graphitized carbon layer grown in situ on the surface of WC-Co composite powder can effectively slow down the abnormal grain growth phenomenon in the sintering process of WC-Co composite powder,and significantly reduce the sintering temperature(1100-1250?).The research results will lay a theoretical foundation for the construction of ultra-thin carbon coated WC-Co cemented carbides production process control system,and the ultimate realization of ultra-thin graphitized carbon layer assisted by the promotion of high strength and high hardness WC-Co cemented carbides.