The oxygen reduction reaction (ORR) is an important energy conversion reaction, especially for fuel cells¹ and metal–air batteries.² Pt-based materials are widely recognized as superior ORR electrocatalysts , hindering this technology's commercialization because of their expensive and scarce nature;³ in addition, these catalysts are not sufficiently stable and exhibit unsatisfactory catalytic activity towards the oxygen reduction reaction (ORR). Certain types of N-containing transition metal catalysts have showed high activity for oxygen reduction in alkaline media,⁴ however, compared to Pt-based catalysts for practical application in fuel cells, both the ORR activity and stability of these catalysts have to be significantly improved.^5,6

 It is believed that the high surface area, high porosity and proper pore structure of catalyst usually lead to high catalytic activity for the ORR. Template method has drawn great attention to obtain the specified morphology and predetermined microstructure.^7,8  In this paper, we choose template method to synthetize polyporous non precious metal catalysts. Nanoscale SiO2 was employed as sacrificial supports to create pores, while chitosan (CTS) as source of N and C.

The CTS-Fe catalysts were prepared by homogeneously dispersion of metal and CTS precursors onto the surface of SiO2. SiO₂ was etched by 5M NaOH after dried at 85 ^oC for 48h, then the resultant powder was pyrolized in an N₂ atmosphere at 800^oC for 1h. The vacated SiO₂ particles lead to creation of pore. The final powder was washed to be neutral by purified water and then dried overnight. Meanwhile, samples pyrolized in an N₂ atmosphere respectively at 700^oC, 900^oC for 1h were prepared by the same procedure. Base on this method, we prepared CTS-Fe catalysts respectively at 700^oC, 800^oC, 900^oC,with high porosity. The kinetics and electrocatalytic activity on the M-PEI catalysts have been measured using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and rotating disk electrode (RDE). All these tests were carried out in a glass cell consisting of a three-electrode system in 0.1M KOH at the ambient solution temperature.

References

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