Performance Of Polymer-derived Heteroatom-doped Carbon Materials For Oxygen Reduction Reaction

Fuel cell is a novel type of energy converting device and has a brilliant prospect in application.Fuel cell also has the advantages of simple structure,low/zero emission and high energy density.At present,Pt-based catalyst is one of the common used cathodic catalysts,however,it suffers from its high cost and is susceptible to methanol and CO poisoning.N-doped or N/P-codoped carbon materials are regard as one of the most promising metal-free catalysts to replace Pt-based catalysts due to their excellent catalytic activity towards oxygen reduction reaction（ORR）,low-cost,and good tolerance for methanol and CO poisoning.In this thesis,organic porous polymers,poly（melamine-formaldehyde）s,were used as single precursors to synthesize N-doped carbon（N/C）and N/P-codoped carbon（N-P/C）catalysts.In addition,the catalytic activities of these catalysts towards ORR in alkaline media were also investigated.The main research contents are shown as follows:（1）Preparation and ORR performance of the N-doped carbon materials derived from PMDP and PMTP.In this chapter,organic porous polymers,poly（melamine-2,6-diformyl-4-methylphenol）（PMDP）and poly（melamine-triformylphloroglucinol）（PMTP）,were firstly synthesized by polymerization of melamine with 2,6-diformyl-4-methylphenol and triformylphloroglucinol,respectively,in DMSO.BET test results indicated that the specific surface area,total pore volume,and average pore size of the PMDP and PMTP were found to be 671 and 302 m2 g^-1,2.10 and 2.16 cm3 g^-1,and 13 and 20 nm,respectively.Followed by separate pyrolysis the two polymers,PMDP and PMTP,give two types of N-doped carbon catalysts,N/C_PMDP and N/CPMTP.BET analysis showed that the specific surface area and total pore volume of the N/C_PMDP and N/CPMTP catalysts were found to be 833 and 464 m2 g^-1,and 1.57 and 2.31 cm3g^-1,respectively.XPS analysis indicated that the N contents of the N/C_PMDP and N/CPMTP catalysts were found to be 4.03 and 2.68 at.%,respectively.In alkaline media,the onset potential,half-wave potential,and limiting current density of N/C_PMDP and N/CPMTP catalysts towards ORR were found to be 0.007 and 0.002 V（vs.Ag/AgCl）,-0.10 and-0.11 V（vs.Ag/AgCl）,6.98 and 5.86 mA cm-2,respectively,with ORR catalytic activity both higher than that of commercial Pt/C catalyst.（2）Preparation and ORR performance of the N/P-codoped carbons derived from PMHP.Firstly,poly（melamine-hexaaldehyde cyclotriphosphazene）（PMHP）was firstly synthesized by using the method described in above chapter.The N/P-codopedcarbon（N-P/C）catalyst was then fabricated by the pyrolysis of PMHP at high temperature.BET analysis showed that the specific surface area and total pore volume of the N-P/C catalyst were found to be 658 m2 g^-1 and 1.48 cm3 g^-1,respectively.XPS analysis indicated that the N and P contents of the N-P/C catalyst were found to be5.57 and 1.32 at.%,respectively.In alkaline media,the onset potential,half-wave potential,and limiting current density of the N-P/C catalyst towards ORR were found to be 0.017 V（vs.Ag/AgCl）,-0.10 V（vs.Ag/AgCl）,and 6.57 m A cm-2,respectively,showing ORR catalytic activity slightly higher than that of commercial Pt/C catalyst.