A template-free I2-assisted pyrolysis strategy to synthesize coral-like nitrogen-doped carbon with a regulated hierarchical porous structure toward efficient oxygen reduction
A template-free I2-assisted pyrolysis strategy to synthesize coral-like nitrogen-doped carbon with a regulated hierarchical porous structure toward efficient oxygen reduction
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DOI：
10.1016/j.cej.2022.135852
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发表时间：
2022-03
影响因子：
15.1
通讯作者：
Z. Su;Guanying Ye;Suqin Liu;Zhen He
中科院分区：
文献类型：
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作者：
Z. Su;Guanying Ye;Suqin Liu;Zhen He
在N掺杂碳(N/C)催化剂中构建多层孔结构对促进电催化反应动力学具有重要意义。然而，现有的许多用于合成多孔碳网络的模板方法通常操作复杂，并且可能会在后处理过程中破坏N/C的催化活性中心(例如，在苛性条件下去除模板)。在这里，开发了一种无模板的I2辅助热解策略来调节分子筛咪唑骨架热衍生的N/C的形态和孔结构。在热解过程中，气相I2I可控制地吸附(通过调节吸附温度)到沸石咪唑骨架的多孔结构中，然后腐蚀骨架。未经任何后处理的N/C具有珊瑚状的形貌、较大的孔容和以中孔/大孔为主的孔结构，由于活性中心的有效暴露和传质能力的增强，对氧还原反应具有良好的电催化性能，半波电位为0.868埃V。以合成的珊瑚状N/C为正极催化剂组装的镁空气电池具有123mW cm−2at 0.73V的优异峰值功率密度。这种I2辅助热解策略可广泛应用于调节来自不同多孔前驱体的碳材料的孔结构和形貌，用于能量转换和存储应用。
Construction of hierarchical porous structures in N-doped carbon (N/C) catalysts is of great significance to promote the reaction kinetics during the electrocatalysis. However, many existing template methods used to synthesize porous carbon networks are usually complicated in operation and might undermine the catalytic active sites of N/C in the post-treatment processes (e.g., templates removal under caustic conditions). Herein, a template-free I2-assisted pyrolysis strategy is developed to regulate the morphology and porous structure of N/C thermally derived from zeolitic imidazolate frameworks. Gas-phase I2is controllably adsorbed (by adjusting the adsorption temperature) into the porous structure of the zeolitic imidazolate frameworks and then corrodes the frameworks during the pyrolysis. The as-synthesized N/C without any post-treatment features a coral-like morphology, a large pore volume, and a meso/macropore-dominated porous structure, rendering excellent electrocatalytic performance toward oxygen reduction reaction with a half-wave potential of 0.868 V vs. RHE due to the effective exposure of active sites and enhanced mass-transfer capability. A Mg-air battery assembled with the as-synthesized coral-like N/C as the cathode catalyst exhibits an excellent peak power density of 123 mW cm−2at 0.73 V. This I2-assisted pyrolysis strategy could be widely applicable for regulating the porous structure and morphology of carbon materials derived from different porous precursors for energy conversion and storage applications.