N-doped 3D Porous Carbon Suppurted Pt Catalyst For Methanol Electro-Oxidation

Direct methanol fuel cells?DMFCs?are power generation devices that convert chemical energy directly into electrical energy.With abundant fuel sources,high power density and energy density,and easy storage and portability,it is most likely considered to be one of the power cells of the new generation.It is generally accepted that Pt is the most effective electrocatalyst for methanol oxidation reactiom?MOR?.However,some obstacles still be addressed in designing an effective Pt catalyst,for example,a high loading of Pt is required for a excellent caralysr for MOR,which increase the cost of DMFC;the carbon intermediate absorbed on the surface of Pt,decrease the active-site;the noble metal nanoparticles may dissolution,migration,and agglomeration cause by the weak interaction between metal-support,At present,the Pt-based catalyst is always the first choice for DMFCs,which hinder the commercialize of DMFCs.Suitable support materials may solve these problem.Therefore,designing an excellent catalyst carrier material is of great importance.The porous carbon material has good conductivity and high specific surface area,not only can provide nucleation sites for the crystallization of Pt,but also can accelerate the mass transfer rate in methanol oxidation process.Besides,nitrogen doping can be beneficial to the deposition of Pt and enhance anchoring of Pt to the support.Further more,it can decreased catalyst particle size and facilitated the dispersion of Pt.Based on this,the main contents of this thesis are as follows:?1?We used nano-silica particles?diameter of about 15 nm?as a sacrificial template,then the silica template was etched with NaOH after high-temperature carbonization to obtain three-dimensional nitrogen-doped carbon?SMNC?with well-developed pore structure,and Pt/SMNC was prepared by microwave assisted method.The morphologies of catalyst were investigated by SEM,TEM,XRD,Raman measurement.The electrochemical properties of the catalyst were characterized by CV,I-t.SEM images and BET show that the SMNC has more developed reticular pore structure,TEM images show that a large number of smaller size Pt nanoparticles uniformly distributed in the SMNC carrier.This loose porous special morphology to shorten charge and mass transfer channels in the catalytic oxidation process to promote the electron and mass transfer efficiently.The electrochemical test indicated that the electrochemical activity surface area is 114.5m²g^-1,the current density for methanol oxidation is 528 mA·mg^-1 Pt.Therefore,Pt/SMNC catalyst has more superior performance than the catalyst prepared without the template.?2?The hollow polyhedron was prepared using the Co metal-organic framework?Co-MOF?rods and glucose spheres as template.The Pt/NC catalysts were obtained by a microwave-assisted polyol process after carbonization and etching of nitrogen-doped hollow porous carbon.The morphologies of catalyst were investigated by SEM,TEM,XRD,XPS measurement.The electrochemical properties of the catalyst were characterized by CV,I-t.Results have shown that the catalyst has excellent methanol oxidation performance,the electrochemically active specific surface areas of Pt/NC is64.3 m²g^-1 and the mass activity has reached 550mA mg^-1 Pt,which suggest that the Pt/NC catalyst is a promising catalyst for methanol oxidation.