Preparation Of Transition Metal Nitrogen Doped Carbon Based Materials And Their Electrocatalytic Activity For Oxygen Reduction Reaction

As one of the most promising energy conversion technology,fuel cells have draw many attention,due to their advantages of environmental friendly,high conversion efficiency,etc.The device could utilization of hydrogen efficiently via convert the chemical energy into electrical energy directly.Oxygen reduction reaction(ORR)plays an vital role for fuel cells,in which the nobel metal catalysts are still the best oxygen reduction reaction catalysts.However,the scarcity source and high cost of nobel metal ctatalysts even the sluggish kinetics of oxygen reduction reaction process,severly limits the commercialization application of fuel cells.In this regards,developing and exploring low cost,extensive source,high efficiency and durable of nobel catalysts is thus of great importance,which has extraordinary actual significance and application prospects.As for cathode oxygen reduction reaction catalysts,the non nobel metal based catalysts have been widely studied in academic interests,due to their high catalytic activity,stability and methanol toxicity.Based on the state of the current progress in the fields of non nobel metal based catalysts as well as the research basis of our owngroup,in this dissertation,we choose carbon nanotube the main carbon sources,and a series of highly efficiency transition metal carbon based catalysts were successfully prepared via introduce heteroatom into transition metal carbon skeleton.The main research contents and achievements are listed as following aspects:1.The nitrogen and sulfur co-doped cobalt/carbon catalysts(Co/S/N)was successfully synthesized by using carbon nanotubes,cobalt sulfamate and dicyandiamide as raw materials,following by the simple ultrasonic dispersion,evaporation solvent and a further calcination process.The final product was characterized by Scanning electron microscopy,Transmission electron microscopy,X-ray diffraction and BET specific surface area test.The ORR performance of the final product was tested in alkaline media.The electrochemical test results demonstrate that the typical catalyst has superior oxygen reduction reaction performance with a high limiting diffusion current density of-5.43 mA cm-2 in alkaline medium,and electron transfer number near 4.The typical catalyst revealed excellent tolerance to methanol poisoning and long term durability.Moreover,the typical catalyst presents excellent oxygen reduction reaction performance in acid media.As a result,the nitrogen and sulfur co-deped cobalt/carbon based catalyst with mesoporous one demensional nanotube structure,which would has an application prospect in the field of oxygen reduction reaction.2.A novel foamelike iron carbide nanoparticles nitrogen doped agar(labed as Fe/C-NA)composite has been successfully prepared via a simple self-explanding method using ferric acetylacetonate and biomass agar as precursors.The iron acetylacetonate can be dispersed uniformly in agar,which could avoid the aggregation of nanoparticles.The BET specific surface area of typical Fe/C-NA-1000 is up to 1327.7 m2 g-1 with mesoporous,and N contents in Fe/C-NA-1000 is 3.09%,respectively.The foam structure of the typical catalyst can improve its conductivity as well as enhance the transfer of ions and electrons.At the same time,the additional doping iron and carbon considerably promoted the formation of more Fe-C active sites.The typical catalyst exhibits outstanding ORR activity in alkaline medium,with the onset potential is comparable to that of commercial Pt/C(20 wt%),and the limiting diffusion current can reach-5.34 mA cm-2,which is slightly lower that of Pt/C of 5.47 mA cm-2;the typical catalyst displays excellent methanol resistance and the stability also eahanced with a limiting diffusion current retention rate of 91.4%after 5000 cycles,the ORR were carried out almost according to the four electron process.In addition,the typical catalyst exhibits excellent oxygen reduction reaction performance,long term durability and methanol tolerance in acid media.3.A novel one-dimension nitrogen doped carbon nanotubes supported Fe based nanoparticles material(FexCyNz/N-CNT)was successful synthesized via ferrocene as an iron source in a hydrothermal route,followed by a grinding process and a further pyrolysis treatment in argon atmosphere.By controlling the molar ratio of ferrocene/dicyandiamide and annealing temperature,the optimal FexCyNz/N-CNT-1000 was obtained.The electrochemical test results demonstrate that the optimal FexCyNz/N-CNT-1000 possesses a remarkable electrocatalytic performance for ORR,limiting current density is even higher than that of commercial Pt/C(0.54 mA cm-2),high electron-transfer number(close to 4),excellent tolerance to methanol,and long-term stability compared to Pt/C.More interestingly,it was found that when the typical material filler loading is 12 wt%,the FexCyNz/N-CNT-1000/wax matrix displays an excellent EM wave absorption performance.Therefore,the FexCyNz/N-CNT-1000 material could regard as high efficient ORR catalyst as well as electromagnetic wave absorber.Such a novel bifunctional nanomaterial system may open a path for rationally designing multifunctional materials for target applications.