Co-VN encapsulated in bamboo-like N-doped carbon nanotubes for ultrahigh-stability of oxygen reduction reaction
Co-VN encapsulated in bamboo-like N-doped carbon nanotubes for ultrahigh-stability of oxygen reduction reaction
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Co-VN封装在竹状氮掺杂碳纳米管中，用于氧还原反应的超高稳定性
DOI：
10.1039/c7nr09538d
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发表时间：
2018
期刊：
影响因子：
6.7
通讯作者：
Fu Honggang
中科院分区：
文献类型：
--
作者：
Wang Ying;Wang Lei;Tong Miaomiao;Zhao Xiaojun;Gao Yanting;Fu Honggang
碳基非贵金属复合材料对氧还原反应（ORR）的电催化活性与公认的Pt/C催化剂相差甚远。因此，有必要开发基于多组分碳基复合材料的新型催化剂，同时具有高活性和高稳定性。本文采用自下而上的策略，采用三聚氰胺作为氮源和碳源，构建了具有少量包裹的Co和VN纳米颗粒的竹状N掺杂石墨碳纳米管（即NGT-CoV）。在合成过程中，三聚氰胺首先与钴和钒离子配位，然后分解成氮化碳纳米片结构。同时，钴离子/簇通过产生的还原气体转化为金属纳米催化剂，其进一步重排氮化碳纳米结构以形成N掺杂的CNT。钒物种的存在通过增强Co和N物种之间的相互作用，强化了电子结构，增加了Co和N物种的含量。优化后的NGT-Co 35 V65 -45-900在ORR中的Eonset为0.92 V（vs. RHE），E1/2为0.81 V（vs. RHE），Tafel斜率为66.1 mV dec−1。它还显示出比商业Pt/C催化剂高得多的耐久性（在10 000次循环后E1/2的负移仅为11 mV）和甲醇耐受性。 这种优异的性能应归功于Co-N、VN和N掺杂的竹节状石墨碳纳米管中活性中心的高暴露水平。此外，由中空石墨化超长碳纳米管构成的骨架不仅可以提供顺畅的质量传递路径，还可以促进快速的电子传递。
The electrocatalytic activity of carbon-based non-precious metal composites towards oxygen reduction reaction (ORR) is far from that of the recognized Pt/C catalyst. Thus, it is necessary to exploit novel catalysts based on multicomponent carbon-based composites with both high activity and high stability. Herein, a bottom-up strategy was used for constructing bamboo-like N-doped graphitic CNTs with a few encapsulated Co and VN nanoparticles (namely, NGT-CoV) by adopting melamine as both a nitrogen source and a carbon source. During the synthesis, melamine initially coordinated with cobalt and vanadium ions and then decomposed into carbon nitride nanosheet structures. Simultaneously, cobalt ions/clusters were converted into metal nanocatalysts by the reduced gases that were generated, which further rearranged the carbon nitride nanostructures to form N-doped CNTs. The presence of vanadium species strengthened the electronic structure and increased the contents of Co and N species by enhancing the interactions among Co and N species. The optimized NGT-Co35V65-45-900 exhibited an Eonset of 0.92 V (vs. RHE), an E1/2 of 0.81 V (vs. RHE), and a Tafel slope of 66.1 mV dec−1 in the ORR. It also displayed much higher durability (a negative shift in E1/2 of only 11 mV after 10 000 cycles) and methanol tolerance than a commercial Pt/C catalyst. The excellent performance should be attributed to the high exposure level of active sites that originated from Co–N, VN and N-doped bamboo-like graphitic CNTs. Moreover, the skeleton composed of hollow graphitic ultra-long CNTs could not only provide smooth mass transport pathways but also facilitate fast electron transfer.