Template Synthesis Of Hierarchically Porous Carbon-based Materials And Their Performance For Electrocatalytic Oxygen Reduction

Extensive efforts have been devoted to explore porous carbon-based materials for oxygen reduction reaction?ORR? in order to replacing the expensive Pt/C catalysts for the commercialization of fuel cell. And some of them have shown excellent catalytic activities, high stabilities, and good methanol resistance. However, the main obstacle for porous carbon-based catalysts is how to develop new low-cost precursors with simple synthesis to produce ORR catalysts with improved electrocatalytic performance.In this thesis, hierarchically porous carbon-based materials co-doped using N and other elements were synthesized by templates using the new low-cost protic salts as the single precursor. By changing the templates as well as the heating temperature, we have achieved controlling the morphology, pore size, contents and types of doped heteratoms. Further, the effects of structure and composition on the electrocatalytic performance have been investigated systematically.?1? The ordered macroporous carbon named NSAC was prepared by using p-phenylenediamine sulfate as the single precursor, which was synthesized by simple acid-base neutralization, with SiO₂ as the hard template. The nitrogen and sulfur were in-situ doped into the carbon by using the single precursor. By changing the size and amounts of SiO₂ and temperature we could change the morphology, specific surface area and surface composition of the products in order to improve the catalytic performance. At last we found that the interconnecting and open structure causing more exposed catalytically active sites could make NSAC, with a similar limiting current density but slightly negative onset potential compared to Pt/C.?2? The mesoporous carbon nanoflakes named NSFC were prepared by using FeCl₃ as the 2D template and p-phenylenediamine sulfate as the single precursor. By changing the amounts of FeCl₃ and temperature we could control the thickness of nanosheets, pore-size distribution and doped state of N/S/Fe of the products in order to explore the structure-activity relationship between the structure, composition and catalytic performance. At last, we found that thin nanosheets were exfoliated and a large number of uniform mesopores formed by using FeCl₃ resulting in a improved specific surface area to promote the diffusion of reactants. Moreover, the Fe species induced the formation of active Fe-Nx centers so that the NSFC showed a more positive onset potential but a slightly smaller limiting current density compared to Pt/C.?3? The hierarchically porous carbon-based hybrid carbon named NSHC was prepared via a dual-template method. By changing the kind and amounts of the templates we explored the unique advantages of the dual-template in controlling the structure and surface composition of the products. At last we found that the enhanced interface interaction between NSAC and NSFC causing more open and exposed active sites to facilitate the fast transport of charges so that NSHC showed a more excellent catalytic activity and higher stability than Pt/C.