Preparation And Electrochemical Performance Of Pt-WC/MMT Composites

Tungsten carbide?WC?has received a great interest due to its platinum-like catalytic activity and higher resistance to CO and H₂S poisoning.However,its much lower catalytic activity than that of Pt,makes how to improve its catalytic performance become a hot topic in recent years.Montmorillonite?MMT?is a natural mineral silicate with a layered-structure on nanoscale,which has many excellent properties,such as electronegative surface,huge specific surface area and strong adsorbability and so on.WC/MMT composites with large surface area and good WC dispersion were prepared through an impregnation approach combined with a reduction-carbonization method using exfoliated MMT as a support.In addition,Pt-WC/MMT composites were prepared by loading Pt on the surface of the WC/MMT composites.The samples were characterized by X-ray diffraction,scanning electron microscope and transmission electron microscope.And their catalytic activity for methonal oxidation was tested by cyclic voltammetry.The main results of above mentioned researches are as follows:?1?MMT was exfoliated by lithium chloride via hydro-thermal method.The results showed that the layer thickness of exfoliated MMT was around 10 nm,of which the surface area increased from 10.56 m²/g to92.53 m²/g.?2?WC/MMT and Pt-WC/MMT composites were prepared using exfoliated MMT as a support,WCl₆ as W source and H₂PtCl₆ as Pt source.The results showed that 10 mmol/g WC/MMT sample,which was prepared when the reaction temperature was 1073K,reaction time was 5 h,and CH₄/H₂ was 20:80,owned both well WC dispersion and coverage.The diameter of WC particles in this WC/MMT sample was about 61 nm and the Pt diameter was about 4nm.?3?Cyclic voltammetry results showed that both WC/MMT and Pt-WC/MMT composites had stable electrocatalytic activity for methanol electrocatalytic oxidation in acidic solution.The peak current density of 10mmol/g sample were 1.121 A·cm^-2 and 0.787 A·cm^-2,which for 5%Pt-WC/MMT sample were 1.121 A·cm^-2 and 0.787 A·cm^-2.In summary,the catalytic activity of WC can be effectively improved by composited with MMT and modified by Pt,indicating that montmorillonite might be a promising supporter for preparing other composites.