Preparation And Properties Of Platinum Catalyst Supported By Aerogels

The ease of use of direct alcohol fuel cells（DAFCs）holds great promise,and their abundant fuel source and low environmental impact make them one of the hot spots for research.In a direct ethanol fuel cell,for example,ethanol is used as a fuel at the anode to produce an oxidation reaction and oxygen is used as an oxidant at the cathode to produce an oxygen reduction reaction.The catalytic layer containing both cathode and anode catalysts plays an important role in the overall fuel cell electrode reaction process.In general,the anode catalytic activity will be somewhat lower than the cathode catalytic activity,and one of the core issues driving the practical promotion and development of fuel cells lies in improving the efficiency of the catalytic activity of the anode catalyst,therefore,the development of efficient anode electrocatalysts is an important issue in the research and promotion of direct alcohol fuel cells.Noble metal-based catalysts are considered the best choice for direct alcohol fuel cell catalysts due to their high activity and stability,and the most widely used catalysts are still the noble metal platinum-based catalysts.However,commercial platinum catalyst prices remain high and there is an urgent need to further reduce the cost of producing platinum catalysts or to further improve the performance of platinum catalysts so as to reduce the amount of precious metal platinum used.It can reduce production costs or improve performance per unit of platinum,thereby reducing the amount of precious metal platinum used.Current research mostly uses Pt-based multi-component catalysts to reduce the amounts of noble metals,and uses materials with high specific surface area and high conductivity as carriers to increase active sites.Therefore,in this paper,aerogel-loaded two-component catalysts containing platinum were prepared using nickel aerogel and carbon aerogel as carriers,respectively,and the content of platinum was controlled.In addition,the morphology,composition and content of the catalysts were analyzed using different characterization methods.The catalytic performance of the catalysts in the electro-oxidation reaction of ethanol in alkaline environments was analyzed and evaluated to obtain aerogel-loaded platinum catalysts with the suitable components and best performance.The specific research contents are as follows:（1）Using nickel chloride hexahydrate and chloroplatinic acid as raw materials and Na BH₄ as reducing agent,Pt@Ni was prepared by self-gelling method and in-situ exchange method,then the platinum content was regulated by controlling the concentration of metal precursor and the replacement time.Finally,through a series of technological processes such as solution exchange and supercritical drying,platinum-nickel aerogel（Pt@Ni）is obtained.SEM and TEM shows that Pt@Ni has a porous structure similar to Ni aerogel.HRTEM,XRD and XPS show that Pt is mainly distributed on the surface of nickel aerogels in a thin film shape,and most of the Ni metal is inside the aerogels.（2）The prepared Pt@Ni in different proportions was applied as an anode catalyst in the catalytic ethanol electro-oxidation reaction process and showed good catalytic performance.When the replacement time was four hours,the Pt@Ni-4h obtained relatively optimal catalytic activity,with a peak current density 1.33 times higher than that of a commercial Pt/C catalyst which contains 20%Pt content,while its ECSA is also higher than that of commercial Pt/C catalyst.（3）Using carbon aerogel with high specific surface area as the carrier,bismuth nitrate pentahydrate and chloroplatinic acid as the precursors,and Na BH₄ was used as reducing agent for the rapid preparation of carbon aerogel-loaded platinum-bismuth catalysts（PtBi@CA）by a one-step reduction method,and the platinum content was adjusted by controlling the concentration of the metal precursors.XRD,XPS and ICP characterizations shows that platinum and bismuth were successfully loaded on the surface of carbon aerogels and partially formed alloys.The results of TEM show that all catalysts have a uniform distribution of metal particles with a particle size of about 2～4 nm on their surface.（4）The PtBi@CA composite with the smallest crystallite size was used as a catalyst to catalyze the ethanol oxidation reaction,and the peak current density of PtBi@CA（50-50）reached64.336 m A·cm^-2,which was 9.49 times that of the Pt@CA catalyst maked under the same experimental conditions and was 11.22 times that of commercial Pt/C.The ECSA value of PtBi@CA（50-50）is 1.5 times higher than that of commercial Pt/C and remains higher than commercial Pt/C after 100 cycles and 500 cycles.The current density of all kind of PtBi@CA catalysts after reaching the steady state is lower than that of Pt@CA,but still higher than that of commercial Pt/C,especially the PtBi@CA（50-50）.This indicates that the addition of Bi can increase the active sites of Pt@CA,making PtBi@CA have good electrocatalytic activity and stability.In conclusion,the highly active platinum-supported two-component catalysts supported by carbon aerogels and nickel aerogels have been successfully prepared.Compared with commercial Pt/C catalysts,the prepared catalysts have much less precious metal Pt content and high electrocatalytic activity.