Pt Loaded Ordered Mesoporous Carbon Prepared By Molecular Assembly For Electrocatalytic Reactions

The continuous exploitation of traditional energy sources,such as coal,oil,and natural gas,as well as the excessive consumption of fossil fuel have resulted in serious environmental problems.Therefore,exploring high-energy storage devices has gained increasing attention.Fuel cells have been widely used in many fields because of their high power density and eco-friendly.To improve energy storage space,energy density,long-term cycling stability and safety,developing better electrodes for batteries is of significant importance.Up to now,the electrode catalysts in fuel cells are mainly based on Pt-based materials.However,the high cost and low stability of Pt-based catalysts seriously hindered the large application of fuel cell.To improve the activity of the catalyst while maintaining a high stability,the alloying of Ptand the optimization of carbon support have become the key to the current catalyst research.Ordered mesoporous carbon materials have been widely studied for its adjustable pore size,high surface area,and easy functional modification,which can finely disperse catalytic metal particles and improve reaction activity.The highly developed mesoporosity is conducive to the transport of reactants and products.Based on this,this paper mainly carried out the following two aspects of work:（1）Using the solvent evaporation self-assembly method,SiO₂colloidal crystals as the hard template,triblock copolymer F127 as the soft template,a multi-stage pore structure（PtIr-OMC）with large pores ordered mesoporous carbon supported PtIralloy can be synthesized through a skillful three-step mehod:i)the metal precursors and carbon precursors assembled spontaneously with F127,respectively;ii)high temperature carbonization;iii)template etching.Due to the restricted effect of the mesoporous carbon framework,the size of alloy particles in the pores can be well controlled to form monodisperse Pt-based alloy nanoparticles.To explore the electro catalysis EOR performance,the PtIrRh-OMC catalyst was synthesized by changing the ratio of PtIrmetal precursor and adding Rh element.Using physical analysis methods combined with electrochemical tests,we explored the relationship between the structure and EOR catalytic activity.The prepared PtIrRh-OMC catalyst has ultra-small size of2.39 nm and distributed uniformly in the pores of ordered mesopores.Its excellent EOR activity can be attributed to the ultra-small particles of PtIrRh alloy and the uniform distribution,which exposed more active sites.Moreover,the ordered multi-level pore structure is conducive to the mass transfer,and the doping ofIrand Rh can help break the C-C bond during the EOR process.（2）Using nanoemulsion self-assembly method,SiO₂ nano spheres as hard template,the block copolymer F127/TMB/polydopamine composite micelles self-assemble on the surface of SiO₂.The F127-polydopamine micelle can be easily carbonized into small carbon nanobubbles（CNBs）by thermal treatment in nitrogen atmosphere.The nitrogen-doped ordered mesoporous carbon balls（OMCS）can be obtained after removing the SiO₂ template.Afterward,ethylene glycol was used as the reductant to uniformly load Ptparticles on ordered mesoporous carbon spheres.Physical analysis methods combined with electrochemical measurements were employed to explore the relationship between the structure and ORR catalytic activity of the catalyst.The Ptnanoparticles in the Pt-OMCS catalyst are uniformly dispersed on the OMCS with ultra-small particle size of 1.35 nm.The catalytic activity of the oxygen reduction reaction is significantly improved compared to commercial Pt/C.This ultra-thin ordered mesoporous carbon layer structure can restrict the growth of Ptparticles and improving the utilization of Pt.Moreover,the mesoporous restricted Ptparticles are hard to agglomerate,making the catalyst excellent ORR stability.