Direct synthesis of a carbon nanotube interpenetrated doped porous carbon alloy as a durable Pt-free electrocatalyst for the oxygen reduction reaction in an alkaline medium
Direct synthesis of a carbon nanotube interpenetrated doped porous carbon alloy as a durable Pt-free electrocatalyst for the oxygen reduction reaction in an alkaline medium
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DOI：
10.1039/c7se00249a
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发表时间：
2017-08
影响因子：
5.6
通讯作者：
Sreekuttan M. Unni;G. Anilkumar;M. Matsumoto;Takanori Tamaki;H. Imai;Takeo Yamaguchi
中科院分区：
文献类型：
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作者：
Sreekuttan M. Unni;G. Anilkumar;M. Matsumoto;Takanori Tamaki;H. Imai;Takeo Yamaguchi
据报道，由单一前体三金属沸石咪唑骨架（t-ZIF）直接合成用于氧还原反应（ORR）的高度耐用的碳纳米管互穿多孔碳合金电催化剂。使用单一前驱体可以改善活性反应中心的均匀分布，这对于 ORR 催化剂至关重要。 t-ZIF具有Fe、Co和Zn金属中心和2-甲基咪唑作为配体。 t-ZIF 在惰性气氛下碳化产生氮气和 Fe/Co-Nx 掺杂碳/碳纳米管，与包裹在碳结构内部的金属/金属氧化物颗粒形成合金 (FeCo-NCZ)。 t-ZIF 中锌的存在会在碳化过程中引起碳的孔隙度。具有相当高表面积的独特形态提供了有效的传质和互穿碳纳米管辅助催化剂中的快速电子传输。 X射线光电子能谱表明，FeCo-NCZ在催化剂表面富集了不同可能的活性反应中心，例如吡啶、石墨和Fe/Co-Nx型氮配位。 FeCo-NCZ 在氧饱和的 0.1 M KOH 中的 ORR 活性与参考 Pt/C 催化剂相当/更高。与 Pt/C 和其他对照样品相比，FeCo-NCZ 显示的起始电位（1.04 V 相对于 RHE）和半波电位（0.91 V 相对于 RHE）更为正。值得注意的是，FeCo-NCZ 的分子氧还原动力学与 Pt/C 的分子氧还原动力学相当，从 Tafel 斜率可以明显看出，并且氧还原遵循四电子路径。更有趣的是，与碱性条件下的 Pt/C 相比，即使在 60 °C 下，FeCo-NCZ 也表现出更好的燃料耐受性和电化学稳定性。
Direct synthesis of highly durable carbon nanotube interpenetrated porous carbon alloy electrocatalysts for the oxygen reduction reaction (ORR) from a single precursor, trimetallic zeolitic imidazole framework (t-ZIF), is reported. The use of a single precursor improves the uniform distribution of active reaction centres which is crucial for ORR catalysts. The t-ZIF has Fe, Co and Zn metal centres and 2-methylimidazole as a ligand. Carbonisation of the t-ZIF under an inert atmosphere produces nitrogen and Fe/Co–Nx doped carbon/carbon nanotubes alloyed with metal/metal oxide particles encased inside the carbon structures (FeCo-NCZ). The presence of Zn in the t-ZIF induces porosity in carbon during the carbonisation process. The peculiar morphology with a reasonably high surface area provides efficient mass transport and interpenetrated carbon nanotube assisted fast electron transport in the catalyst. X-ray photoelectron spectroscopy reveals that FeCo-NCZ is enriched with different possible active reaction centres such as pyridinic, graphitic and Fe/Co–Nx type nitrogen coordination on the catalyst surface. The ORR activity of FeCo-NCZ in oxygen saturated 0.1 M KOH was comparable to/higher than that of the reference Pt/C catalyst. The displayed onset potential (1.04 V vs. the RHE) and half-wave potential (0.91 V vs. the RHE) of FeCo-NCZ are more positive compared to those of Pt/C and other control-samples. It is noteworthy that the dioxygen reduction kinetics of FeCo-NCZ are comparable to those of Pt/C as evident from the Tafel slope and oxygen reduction follows a four electron pathway. More interestingly, FeCo-NCZ shows better fuel tolerance and electrochemical stability even at 60 °C compared to Pt/C under alkaline conditions.