Pyridine Nitrogen Self-doped Non-noble Metal Electrocatalysts For Fuel Cells

Oxygen reduction reaction catalyst in the fuel cell efficiency is a key factor.At the current stage of these technologies,Pt based catalysts are most efficient for ORR.In spite of the great progress achieved in the development of advanced Pt based catalyst,the high price and limited availability of Pt resource still constitutes the major challenge for the commercialization of the technologies.Developing low-cost efficient non-precious metal catalysts for oxygen reduction is crucial challenge.Synthesis of non-noble metal catalysts for oxygen reduction with the performance comparable to that of Pt-based catalysts is an important research direction in the research area of developing the oxygen reduction catalyst.In this work,we report a new strategy of synthesizing highly efficient and robust non precious metal catalysts for the oxygen reduction reaction via the pyrolysis of bis(imino)pyridine metal-based polymers.In the method,bis(imino)pyridine polymer is prepared by the Schiff base condensation of 2 equiv of selected polyamine with 2,6-Diacetylpyridine as a key starting material.The polymer has a typical characteristic of pyridine-based tridentate ligands that have strong coordination to divalent metal ions such Fe,Co and Ni.Examples prepared using this method demonstrated an excellent performance for ORR.Therefore,it is reasonably believed that this strategy can open a new route and provide one more option besides the previously reported methods to explore none precious metal catalysts through selecting the precursor of polyamine.The details are as follows:First example,Fe/DPA-PPA catalyst,was prepared via the pyrolysis of polymeric bis(imino)pyridine Fe ion using 2,6-diacetylpyridine(DPA),p-phenylenediamine(PPA),and FeCl2 as precursors,The catalysts consisted of Fe3C nanoparticles encapsulated by nitrogen-doped carbon layers with nanoparticle size about 20-50 nm.Compared with commercially Pt/C,the non-precious metal catalyst have more positive onset and half-wave positive of 1.05 V(RHE),0.85 V(RHE)in 0.1 M KOH solution,respectively,and slightly lower onset potential and half-wave potential of 0.88 V(RHE),0.70 V(RHE)in 0.5 M H2So4 media,respectively.Meanwhile,the catalyst display remarkable stability performance after 10000 cycles between 0.6 V and 1.0 V(RHE)for ORR.Second example,Fe-C-N and Co-C-N was prepared using 2,6-diacetylpyridine,melamine,ferrous chloride,cobalt chloride hexahydrate as precursors the study found that these catalysts have high nitrogen contents(above 4 atom%),exhibit outstanding electrocatalytic performance and stability toward oxygen reduction reaction in both acidic and alkaline media,Especially in the alkaline solution,the onset potentials of Co-C-N and Fe-C-N catalysts reach 1.03 V and 1.04 V,respectively,and the half-wave potentials are 0.85 V and 0.88 V,respectively.Moreover,the catalyst display remarkable stability performance after 10000 cycles between 0.6 V and 1.0 V(RHE)for ORR,the decay rate of Co-C-N and Fe-C-N half-wave potential is only 4.7%and 2.9%,respectively.It is proved that these method are in favour to prepare high performance of non-noble metal oxygen reduction catalyst.