Template-directing Non-precious Metal Modified Porous Carbon For Catalysing Oxygen Reduction

The hydrogen fuel cell,which has high energy conversion efficiency and zero pollutant emissions,is a new energy conversion device.However,the oxygen reduction reaction(ORR)at the cathode,with a low reaction rate,various reaction steps,and complex reaction intermediate,is the decisive step for the fuel cell’s energy conversion efficiency.At present,the most widely used catalysts for ORR are the expensive platinum-based catalysts.Therefore,to develop non-precious metal carbon-based catalysts,which can replace Pt/C,is of great significance to promote the development of hydrogen fuel cells.Porous carbon with good conductivity,excellent chemical stability,high specific surface area,and easy regulatable components,is a kind of common electrocatalytic electrode material.By adjusting the composition,morphology,and structure of porous carbon materials,better ORR catalytic performance can be obtained.At first,non-precious metal-doped carbon-based materials break the charge distribution and spin density of pure carbon materials,and introduce new catalytic active sites.Furthermore,the porous carbon material can be used as a support to load highly dispersed non-noble metal catalysts and effectively improve active sites’ utilization and stability.Also,optimizing the morphology and structure of porous carbon materials will raise the utilization of active sites.Therefore,constructing suitable pore structures through the template method,can increase the specific surface area of the samples,accelerate the transport of electrons and substances and electrons,and finally improve ORR’s catalytic performance.Based on the above investigation,in this thesis,two non-precious metal-modified porous carbon materials were prepared by template method,and the structure-activity relationship between materials and the ORR catalytic activity was explored.The main results are as follows:1.Ordered macroporous phosphorus-and nitrogen-doped carbon(M-PNC)is prepared successfully by carbonization of double-solvent-induced MOF/polystyrene sphere(PS)precursors accompanied with spontaneous removal of the PS template,followed by post-doping phytic acid.Thanks to the hierarchical structure,high specific surface area,and multiple heteroatom-doping,M-PNC exhibits unusual catalytic activity for ORR in the alkaline solution,comparable to Pt/C catalyst.And the optimized sample shows more excellent stability than Pt/C catalyst.2.A carbon-based catalyst,iron phthalocyanine coated nitrogen-doped hollow carbon sphere(FePc-NHCS)has been fabricated successfully by carbonization of polystyrene@polydopamine precursors,followed by the loading of iron phthalocyanine(FePc).Benefiting from the desired hierarchical structure and high specific surface area of nitrogendoped hollow carbon sphere(NHCS),the stability and dispersion of FePc can be enhanced.Compared with NHCS and FePc coated nitrogen-doped carbon(FePc-NCS),FePc-NHCS is much better in the ORR performance.It not only proves that FePc can effectively elevate the ORR activity of NHCS,but also proves that the hollow structure can promote the mass transfer efficiency,thereby improving the utilization efficiency of active sites.In the alkaline electrolyte solution,FePc-NHCS exhibits ORR catalytic performance comparable to Pt/C.