Synthetise Of Novel Polymer Based Nitrogen Doped Carbon Materials And Their Applications In Oxygen Reduction Reaction

The sluggish oxygen reduction reaction(ORR)demanding high overpotential is a major barrier for large scale application of green energy conversion and storage systems such as fuel cells and metal-air batteries,which necessitates the urgent need for advanced catalysts with efficient activity and high durability.Transition metal-nitrogen-carbon materials(M-N-C)are considered as one of the most promising candidates of non-precious metal(NPM)catalysts for oxygen reduction reaction(ORR).However,in spite of the recent advancements,there is still a big gap between M-N-C and conventional precious metal-based catalysts in terms of both catalytic activity and durability,in particular in acidic media.Although the specific catalytic mechanism of M-N-C based catalysts for ORR has remained controversial.To date the widely recognized active sites include M-N-C,M-Nx,MNX and MCx.The intrinsic catalytic activity,density and interaction of the active sites are determining factors on the catalyst performance,which are closely linked with the type of the precursor.Development of N-containing precursors,therefore,is a straightforward strategy in developing practical M-N-C ORR catalysts.In the thesis,2,6-Diaminopyridine was choosed as a key starting precusor for synthesis of N-containing polymers.By changing polymerization reaction conditions,reaction type ect,a series of polymer-based non-noble metal and nonmetal catalyst with high catalytic activity for ORR were obtained.The research contents mainly include the following three aspects:(1)we report a novel strategy to design new type of precursors at molecular level for synthesizing highly efficient and robust M-N-C ORR catalyst via the pyrolysis of bis(imino)-pyridine metal-based polymers.The Fe-N-C catalyst that comprises the self-supporting characteristics possesses mesoporous structure with high contents of N(4.04 wt%)and Fe(18.64 wt%).The Fe species in the catalyst consist of Fe-Nx moieties and highly dispersed nano/sub-nanosized Fe carbides and nitrides particles embedded onto N-doped carbon matrix,all of which play a crucial role in the final catalytic activity.The catalyst exhibits excellent electrochemical performance for ORR in particularly,which are comparable to commercial Pt/C catalyst in acidic media and superior to commercial Pt/C in alkaline media.Meanwhile,the catalysts show remarkable cycle stability outperforming the commercial Pt/C both in alkaline and acidic media.(2)Two kinds of Fe-N-C catalysts with similar composition,but different structure were synthesized by using 2,6-Diaminopyridine as polymeriztion monomer in the presence of Fe(OH)3 and Fe3+ respectively as metal precursor:1,nitrogen-doped carbon materials decorated with highly dispersed subnanosized iron carbide and iron nitride particles;2,nitrogen-doped graphene like carbon material withl0-50nm sized iron carbide and iron nitride particles.Experimetal tests confirm that particles size of Fe carbides and Fe nitrides play a critical role on the acitivity of catalyst for ORR.Subnano-sized Fe carbides and nitrides significantly enchance the activity of Fe-N-C for ORR.(3)N,S co-doped carbon nanospheres were perpared via pyrolysis of poly 2,6-Diaminopyridine using 2,6-Diaminopyridine as reactant monomer and ammonium persulfate as initiator.Electrochemical measurements show that the N,S co-doped carbon nanosphere as metal free catalyst for ORR has remarkable acitivity for ORR.This method is simple,efficient and suitable for industrial production.