The exploration of efficient, stable, and inexpensive oxygen reduction reaction (ORR) electrocatalysts to replace Pt/C in fuel cells and metal–air batteries still remains an ongoing challenge. Herein, we report an efficient ORR electrocatalyst composed of single-atom FeN_x and γ-Fe₂O₃ nanoparticle co-functionalized hollow graphitic carbon nanofibers (FeN_x/Fe₂O₃-CNFs). It is found that the FeN_x species serve as the active sites, while the γ-Fe₂O₃ nanocrystals function as a co-catalyst to boost the ORR catalytic activity. The obtained FeN_x/Fe₂O₃-CNFs exhibit desirable ORR electrocatalytic activity with a 4-electron transfer pathway, a half-wave potential of 0.81 V approaching that of commercial Pt/C, low hydrogen peroxide yields (<6% at 0.2–0.7 V), long-term stability (87.14% after 30 000 s), and excellent methanol tolerance. The assembled Zn–air battery based on the FeN_x/Fe₂O₃-CNFs has an open circuit voltage of 1.51 V and superior energy density of 920 W h kg⁻¹. This work highlights the significant contribution of the co-catalyst in electrocatalysis.

中文翻译：

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FeNx和γ-Fe2O3共官能化中空石墨碳纳米纤维，可在碱性介质中有效还原氧

探索有效，稳定和廉价的氧还原反应（ORR）电催化剂来替代燃料电池和金属空气电池中的Pt / C仍然是一项持续的挑战。在本文中，我们报道了单原子芬组成的高效的ORR电_X和γ-的Fe ₂ ö ₃纳米颗粒共官能化中空石墨碳纳米纤维（FEN _X / Fe的_2个ö ₃ -CNFs）。据发现，FEN _X物种用作活性位点，而γ-的Fe ₂ ö ₃纳米晶体作为助催化剂，以提高在ORR催化活性起作用。所得的FeN _x / Fe ₂ O ₃-CNFs具有理想的ORR电催化活性，具有4电子转移途径，0.81 V的半波电势接近商用Pt / C的半波电势，过氧化氢产率低（0.2-0.7 V时<6％），长期稳定（3万秒后为87.14％），并具有出色的甲醇耐受性。基于FeN _x / Fe ₂ O ₃ -CNFs的组装锌空气电池具有1.51 V的开路电压和920 W h kg ^-1的出色能量密度。这项工作突出了助催化剂在电催化中的重大贡献。