Iron and nitrogen codoped carbons (Fe–N–C) have emerged as promising noble-metal-free catalysts for the oxygen reduction reaction (ORR). However, delicate control over their structure to enhance the catalytic efficiency is still challenging. Herein, we presented the synthesis of novel ionic-liquid (IL) derived nitrogen and iron co-doped carbon nanotube (CNT) based core–sheath nanostructures that can contribute to solving these challenges associated with the ORR. These nanostructures are synthesized by the adsorption of heteroatom containing ILs on the walls of CNTs followed by carbonization. The advantage of using an IL as a nitrogen source is that the obtained catalyst has a high level of N doping and a high surface area. Electrochemical characterization revealed that the N and Fe codoped CNT based core–sheath nanostructures exhibited superior catalytic activities toward the ORR under both alkaline and acidic conditions. Particularly in alkaline solution, the CNT/Fe–N–C catalysts showed better ORR activity compared to the commercial Pt/C catalyst. We suggest that the excellent electrocatalytic performance of CNT/Fe–N–C catalysts is attributed to: (i) the synergistic effect, which provides more catalytic FeNx sites for the ORR, due to the Fe and N co-doping and (ii) the high surface area and excellent electron transfer rate arising from the IL-derived core–sheath structure.

中文翻译：

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离子液体作为 Fe-N 掺杂碳纳米管电催化剂的前体用于氧还原反应

铁和氮共掺杂的碳（Fe-N-C）已成为有前途的无贵金属的氧还原反应（ORR）催化剂。然而，对其结构进行精细控制以提高催化效率仍然具有挑战性。在此，我们介绍了新型离子液体 (IL) 衍生的氮和铁共掺杂碳纳米管 (CNT) 核壳纳米结构的合成，有助于解决与 ORR 相关的这些挑战。这些纳米结构是通过将含有 IL 的杂原子吸附在 CNT 壁上然后碳化来合成的。使用 IL 作为氮源的优点是所获得的催化剂具有高水平的 N 掺杂和高表面积。电化学表征表明，N 和 Fe 共掺杂的基于 CNT 的核-鞘纳米结构在碱性和酸性条件下都对 ORR 表现出优异的催化活性。特别是在碱性溶液中，与商业 Pt/C 催化剂相比，CNT/Fe-N-C 催化剂表现出更好的 ORR 活性。我们认为 CNT/Fe-N-C 催化剂优异的电催化性能归因于：(i) 由于 Fe 和 N 共掺杂，协同效应为 ORR 提供了更多的催化 FeNx 位点和 (ii) IL 衍生的核-鞘结构产生的高表面积和优异的电子转移率。与商业 Pt/C 催化剂相比，CNT/Fe-N-C 催化剂表现出更好的 ORR 活性。我们认为 CNT/Fe-N-C 催化剂优异的电催化性能归因于：(i) 由于 Fe 和 N 共掺杂，协同效应为 ORR 提供了更多的催化 FeNx 位点和 (ii) IL 衍生的核-鞘结构产生的高表面积和优异的电子转移率。与商业 Pt/C 催化剂相比，CNT/Fe-N-C 催化剂表现出更好的 ORR 活性。我们认为 CNT/Fe-N-C 催化剂优异的电催化性能归因于：(i) 由于 Fe 和 N 共掺杂，协同效应为 ORR 提供了更多的催化 FeNx 位点和 (ii) IL 衍生的核-鞘结构产生的高表面积和优异的电子转移率。