Preparation And Property Study Of Porous Carbon-based Nanomaterials Anodic Electrocatalysts For Alkaline Direct Methanol Fuel Cells

Alkaline direct methanol fuel cells have received much attention because of their advantageous properties including high energy density,high conversion efficiency and easy storage of fuel.However,the anode catalyst still has the problems of high cost and low catalytic activity,which restricts its commercial application.In recent years,porous carbon-based nanomaterials have been considered a very promising application of support for the preparation of highly active Pt-based electrocatalyst because of its unique morphology and physical and chemical properties.In this paper,three kinds of porous carbon-based nanomaterials were synthesized by template method,and the catalyst was used as support to prepare the catalyst of alkaline direct methanol fuel cell.The relationship between the structure,morphology and composition with the catalytic performance of the catalyst were investigated.The specific research contents and results are as follows:1.Preparation of nitrogen-doped porous carbon with functionalized ionic liquid as precursor and its application for electrocatalytic oxidation of methanolAs the ionic liquid has the advantages of low melting point,stable thermodynamic properties and low vapor pressure,we use ionic liquid as carbon source and nitrogen source,and silica nanospheres as hard template.The ionic liquid is coated on the silica nanospheres through the self-assembly process.The nitrogen-doped porous carbon was obtained after carbonization and removing the hard template.The nitrogen content of the material is 2.92wt%,and a high specific surface area of 1515 m² g^-1,which is about 4 times than that of Vulcan XC-72R.After supported Pt,the Pt nanoparticles were uniformly dispersed on the surface of the carbon support.It is used for methanol oxidation in alkaline medium.Compared with commercial Vulcan XC-72R supported Pt?Pt/C?catalyst,it has better stability and catalytic activity,which was likely due to the higher surface area and the porous structure of the carbon support and the interaction between doped nitrogen and metal particles.2.Preparation of nitrogen-doped porous carbon spheres with dopamine as precursor and its application for electrocatalytic oxidation of methanolIn order to further improve the nitrogen content and simplify the preparation of the material,dopamine was used as the carbon and nitrogen source and amphiphilic block copolymer PS₁₇₃-b-PEO₁₇₀ as the soft template.The nitrogen-doped porous carbon spheres were obtained by the self-assembly method.Nitrogen-doped carbon nanospheres have a uniform particle size of about 200 nm,a higher nitrogen content of 6.9 wt%,and a larger specific surface area of 554 m² g^-1.After supported Pt,the Pt nanoparticles were about 2.5 nm in diameter and were uniformly dispersed on the surface of the carbon spheres.The peak current density of the oxidation of methanol was 101 mA cm^-2,which is about 3 times higher than the commercial Vulcan XC-72R supported Pt catalyst?Pt/C?(29 mA cm^-2),when it is used for methanol oxidation in alkaline medium.The high catalytic activity may be due to the combination of honeycomb porous structure and nitrogen doping.In particular,doping of nitrogen is more favorable for the formation of highly dispersed and highly active Pt nanoparticles.3.Porous carbon supported Pt-Pd alloy catalyst for electrocatalytic oxidation of methanolBecause Pt catalyst has the disadvantage of CO poisoning,Pt-Pd is used as the active component of the catalyst on the basis of the improved carbon support,and the bimetallic catalyst is prepared to further improve its catalytic activity and stability.The porous carbon was prepared using the phenolic resin as the carbon source and the silica nanospheres as the hard template,and then the Pt and Pd were supported on it with different atomic ratios.Physical characterization found that the specific surface area of porous carbons was as high as458 m² g^-1,and the metal particles were well distributed on the surface.The electrochemical test showed that the catalyst has the best catalytic activity and anti-CO poisoning when the atomic ratio of Pt to Pd is 3 to 1.The improvement of electrocatalytic activity and stability may be due to the interaction between the electrochemical active area of porous carbon and the synergistic effect of Pt and Pd.