Preparation Of Heteroatom-doped Iron-based Catalysts And Its Performance In ORR

Fuel cell is an energy conversion device with considerable application prospects.It has the advantages of high energy conversion rate,clean and pollution-free,etc.,which is in line with people’s expectations for energy utilization.However,fuel cells are restricted by the slow rate of the oxygen reduction reaction(ORR)at the cathode,so we need to develop efficient oxygen reduction catalysts to improve their performance.Currently,the most commonly used cathode catalysts in the world are platinum-based noble metal catalysts.However,the limited reserves of noble platinum metal and high cost have greatly restricted the widespread use of fuel cells.Therefore,it is urgent to develop stable,inexpensive and high-performance non-precious metal catalysts to solve the above problems.Therefore,this dissertation focuses on non-precious metal iron-based catalysts,and uses doped fluorine(F),nitrogen(N),sulfur(S)and other heteroatoms to co-doped to further improve its oxygen reduction performance,thereby preparing good performance heteroatoms.The thesis mainly includes the following contents:(1)Polyacrylonitrile,perfluorosulfonic acid resin(PFSA)and ferric nitrate nonahydrate were used as raw materials,the precursor was prepared by electrospinning,and the Fe/N/F/S co-doped miscellaneous carbon nanosheet-nanosphere catalyst was successfully prepared by carbonization at high temperature.The results of electrocatalytic performance test showed that the initial potential and half-wave potential of Fe/N/F/S-0.44 were-0.013V and-0.129V,respectively,while initial potential and half-wave potential of commercial catalyst Pt/C-20%were-0.012V and-0.166V,respectively.The initial potential of the Fe/N/F/S-0.44 and commercial catalyst Pt/C-20%is not much different,but the half-wave potential of Fe/N/F/S-0.44 is better than that of the commercial catalyst Pt/C-20%.At the same time,the chronoamperometric test results show that Fe/N/F/S-0.44 has better durability and methanol tolerance than that of the commercial catalyst Pt/C-20%.(2)Sucrose,poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)triblock copolymer(P123),hydrochloric acid and tetraethylorthosilicate(TEOS)were utilized as raw materials.The carbon precursor was successfully synthesized by a one-pot method,and then the precursor was fully stirred with concentrated sulfuric acid,ferric nitrate nonahydrate and urea,and dried and then placed in a nitrogen atmosphere for roasting.After removing the template,an iron-nitrogen co-doped porous carbon catalyst with ORR performance superior to the commercial catalyst Pt/C-20%was obtained.Among them,the initial potential and half-wave potential of the sample Fe-N/C-0.25 are-0.014V and-0.123V,respectively,which are better than the corresponding value of the commercial catalyst Pt/C-20%.And after the stability test of 10000s,the catalyst sample Fe-N/C-0.25 still maintains 91%of the initial current density,which is much higher than the commercial catalyst Pt/C-20%(after 10000s,the current density is reduced to 78%of the initial value).At the same time,the methanol tolerance of Fe-N/C-0.25 is better than that of the commercial catalyst Pt/C-20%.(3)The 2,5-pyridinedicarboxylic acid,urea,KOH and ferric nitrate nonahydrate was regarded as raw materials.the precursor is obtained by a simple molten salt method assisted by one-pot condensation polymerization,and then carbonized at high temperature to obtain iron and nitrogen co-doped porous carbon electrocatalyst.Combined with the characterization of the catalyst,it is found that it has a large specific surface area,which can reach 3641 m~2/g.Among them,the initial potential(-0.008V)and half-wave potential(-0.111V)of the sample Fe/N/C-0.02 are far better than the initial potential(-0.012V)and half-wave potential(-0.166V)of commercial Pt/C-20%.At the same time,the stability and methanol tolerance of the prepared iron-nitrogen co-doped series catalysts are better than commercial catalysts Pt/C-20%.