Preparation And Oxygen Reduction Reaction Performance Of Carbon-based Non-noble Metal Electrocatalysts

Hydrogen energy has the characteristics of wide sources,high calorific value,and environmentally friendly,and it is considered to be one of the clean energy sources most likely to replace fossil fuels.The fuel cell is the most efficient way to use hydrogen energy,which can directly convert the chemical energy in hydrogen into electrical energy.Compared with traditional heat engines,fuel cells have much higher energy density and power generation efficiency.Fuel Cells have now been used in many fields.Successful application,but the high cost of cathode platinum catalyst restricts the commercialization process of fuel cells.Therefore,it is very important to find cheaper alternative electrocatalytic materials for oxygen reduction reactions.The common electrocatalytic materials for oxygen reduction reactions can be roughly divided into three categories:noble metal catalysts,gold compounds,and carbon-based catalysts.Although noble metals have excellent catalytic activity,they have the problems of poor stability and high cost.Metal compounds have good stability in acidic solutions,but their catalytic activity is low.Low-cost,abundant carbon-based catalysts may be the key to the further development of fuel cells.Based on the above background,this thesis prepared a series of carbon-based non-metal and non-noble metal oxygen reduction electrocatalysts and studied their catalytic activity.The details are as follows:1.The nitrogen-rich microporous polymer（PTCA）is synthesized by the reaction of tripolycyanamide monomer（TCA）and paraformaldehyde.The PTCA polymer exhibits a nitrogen content as high as 43.9 wt%.Using PTCA as a precursor,a simple one-step pyrolysis method was used to prepare porous carbons（NOCs）doped with nitrogen and oxygen.The influence of temperature on the structure of porous carbon and electrocatalytic performance of oxygen reduction was investigated.The linear sweep voltammetry（LSV）curve shows that the initial potential(E_onset)and half-wave potential(E_1/2)of the NOCs catalyst relative to the reversible hydrogen electrode（RHE）are 0.942 and 0.853 V,respectively,which are close to the commercial Pt/C catalyst(E_onset=0.944,E_1/2=0.864 V).In the long-term,cycle stability test and methanol resistance test,NOCs showed better stability than Pt/C.2.Using nitrogen-rich microporous polymer（PTCA）as a precursor,based on the metal-chelating ability of N atoms in PTCA,the PTCA loaded Fe Cl₃ was carbonized at high temperature to prepare iron-nitrogen co-doped porous carbon（Fe NCs）.The effect of doping amount and carbonization temperature on porous carbon structure and electrocatalytic performance for oxygen reduction.The linear sweep voltammetry（LSV）curve shows that the onset potential(E_onset)and half-wave potential(E_1/2)of the Fe NCs catalyst relative to the reversible hydrogen electrode（RHE）are 0.936 and 0.851 V,respectively,which are close to the commercial Pt/C catalyst(E_onset=0.944,E_1/2=0.864 V).In the long-term,cycle stability test and methanol resistance test,Fe NCs showed better stability than Pt/C.3.Synthesize Si O₂@PTCA with Si O₂ pellets as a template,load Fe Cl₃ and carbonize it at high temperature,remove the Si O₂ template with Na OH,and prepare iron-nitrogen co-doped mesoporous carbons（Fe MCs）with hierarchical pore structure.The influence of the amount of Si O₂ template on the structure of porous carbon and the electrocatalytic performance of oxygen reduction was investigated.The linear sweep voltammetry（LSV）curve shows that the onset potential(E_onset)and half-wave potential(E_1/2)of the Fe MCs catalyst relative to the reversible hydrogen electrode（RHE）are 0.942 and 0.856 V,respectively,which are close to the commercial Pt/C catalyst(E_onset=0.944,E_1/2=0.864 V).In the long-term,cycle stability test and methanol resistance test,Fe MCs showed better stability than Pt/C.In short,carbon-based non-metal and non-noble metal catalysts based on nitrogen-rich microporous polymer（PTCA）series have been successfully synthesized,and they have shown excellent application prospects in oxygen reduction electrocatalysis.