Abstract
High-performance electrocatalysts for the oxygen reduction reaction (ORR) are essential in electrochemical energy storage and conversion technologies. Fe-N-C electrocatalysts have been developed as one of the most promising alternatives to precious metal materials. Current M-N-C electrocatalysts usually are derived from high-temperature thermal treatment of a nitrogen-containing polymer or metal–organic frameworks (MOFs). Here, we developed Fe-N-C mesoporous nanofibers with low-cost urea and FeCl3 as the nitride and iron source; the electrocatalysts with abundant Fe-Nx active sites and large surface area were synthesized via electrospinning, in situ pyrolysis, and acid treatment process. The use of sealing conditions in the calcination process can effectively improve the nitrogen species content in the catalyst, which is important for improving performance. The as-prepared electrocatalyst material manifests well electrocatalytic performance for ORR in alkaline electrolyte (onset potential of 0.93 V and half-wave potential of 0.82 V); meanwhile, the electrocatalyst expresses good stability and methanol tolerance. This work may provide new thought for developing high-performance ORR electrocatalysts.
Highlights
Fuel cells are of tremendous interest for clean energy conversion devices, and the oxygen reduction reaction (ORR) is the major limiting factor [1]
Precursor solution containing polymer, FeCl3 (Fe source), and urea (N source) was prepared and followed by the electrospinning process, and the precursor nanofibers were obtained; it was transferred into the tube furnace to carbonize the polymer; it should be noted that to pretend the urea volatile under high temperature, a coverage was covered on the top of the crucible; soon afterwards, the obtained black powder was immerse in HCl solution for 5 days to remove the excess metal particle, and the Fe-N-C mesoporous nanofibers were obtained
In conclusion, Fe-N-C mesoporous nanofibers with abundant Fe-Nx active sites and large surface area were synthesized via the electrospinning, in situ pyrolysis, and acid treatment process
Summary
Fuel cells are of tremendous interest for clean energy conversion devices, and the oxygen reduction reaction (ORR) is the major limiting factor [1]. Developing nonprecious metal catalysts with high ORR performance to replace Pt-based catalysts for practical applications is necessary. In this regard, a plenty of works, including transition metal and nitrogen co-doped carbons (M–N/C, M = Fe, Co, Ni) [4–8], metal-free heteroatom-doped carbons [9–11], and metal oxide-carbon composites [12, 13], have been reported for replacing Pt-based catalysts. A plenty of works, including transition metal and nitrogen co-doped carbons (M–N/C, M = Fe, Co, Ni) [4–8], metal-free heteroatom-doped carbons [9–11], and metal oxide-carbon composites [12, 13], have been reported for replacing Pt-based catalysts Among these candidates, the Fe-N-C emerged as the most. Carbon support morphology and pyrolysis temperature affect the active site exposure and the conductivity which further determine the electrocatalyst performance
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