Preparation And Properties Of Fe-N_x/C Non-noble Metal Oxygen Reduction Catalyst

Due to its high efficiency and environmental friendliness,fuel cells are gradually becoming the most promising next-generation energy conversion devices.Catalytic oxygen reduction in alkaline solution is a key cathode reaction in fuel cells,which is used in a wide range of energy technologies.In addition,due to the high overpotential problem in the cathode oxygen reduction reaction,a highly efficient cathode catalyst is sought.At present,Pt and its alloys have been considered to be the most effective commercial catalysts,but Pt has a disadvantage of high cost and insufficient stability,which hinder its large-scale use.Therefore,a large amount of research work have been devoted to finding an effective and inexpensive electrocatalyst.Among them,since non-precious metal catalysts have high catalytic activity,low cost and good durability are receiving more and more attention.In this study,several non-noble metal oxygen reduction catalysts with nitrogen-containing fused-ring compounds as precursors were synthesized by simple and novel methods.Their properties were characterized and studied.The research contents are as follows:(1)A novel non-noble metal oxygen reduction(ORR)catalyst(Fe-PIPhen/C)was synthesized in this work.In this paper,a nitrogen-rich precursor(PIPhen)was used as a ligand by chemical reaction.To synthesize a nitrogen-rich iron coordination complex(Fe-PIPhen),and then load the complex onto the carbon powder to form a target Fe-PIPhen/C catalyst.The results show that Fe-PIPhen/C has good performance,the hydrogen peroxide yield is low,only 2.58%,and the average electron transfer number in alkaline medium is 3.93.(2)The previously reported ligand(PDOC)was operated by oil bath to obtain the target product Fe-PDOC/C.Then,in order to explore the effect of calcination on the electrocatalytic performance,the tube furnace was programmed to be heated to 700?,800?and 900?.Firstly,the surface of the material was characterized by SEM and XPS.After electrochemical test,the catalytic performance of the catalyst after calcination was obviously improved,and the Fe-TPPZ/C-700 catalyst after calcination had the best performance.In summary,this work has initially confirmed that the calcination treatment can further improve the catalytic performance of the oxygen reduction catalyst.(3)In this work,a synthetic nitrogen-rich compound(FPPHA)was used as a precursor to gain an oxygen reduction reaction(ORR)catalyst,and then four composite catalysts were formed through metal coordination and toner loading operations and tube furnace calcination operations.The results show that Fe-FPPHA/C-800 has the best oxygen reduction catalytic performance in the pyrolyzed material,and the average electron transfer number and hydrogen peroxide yield are 3.86 and 6.7%,respectively.In addition,in order to further explore its catalytic mechanism,the Fe-FPPHA/C-800 catalyst was subjected to pickling operation.The results show that the catalytic activity of the catalyst after pickling was reduced,indicating that the oxides and carbides produced during the calcination process also acted as a catalyst.(4)Firstly,a triazine-containing nitrogen-containing compound(pytpy)was synthesized by an inorganic reaction,and then the complex Fe-pytpy/C was obtained by a complexation reaction of a metal ion and a carbon powder loading operation,followed by a pyrolysis operation to obtain Fe-pytpy/C-700,Fe-pytpy/C-800 and Fe-pytpy/C-900 catalysts.The physical and electrochemical characterization of the prepared materials show that the performance of Fe-pytpy/C-700,Fe-pytpy/C-800 and Fe-pytpy/C-900 catalysts was better than that of Fe-pytpy/C.And the performance of the Fe-pytpy/C-800 catalyst is optimal,and the reaction pathway follows the four-electron path.