An efficient carbon-based ORR catalyst from low-temperature etching of ZIF-67 with ultra-small cobalt nanoparticles and high yield
An efficient carbon-based ORR catalyst from low-temperature etching of ZIF-67 with ultra-small cobalt nanoparticles and high yield
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DOI：
10.1039/c8ta10925g
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发表时间：
2019-02-28
影响因子：
11.9
通讯作者：
Guo, Zhengxiao
中科院分区：
文献类型：
--
作者：
Guo, Jian;Gadipelli, Srinivas;Guo, Zhengxiao
报道了一种简单且可控的低温(450℃)路线，在氮掺杂的超多孔石墨网络(Co3O4/Co@N-G-450)中制备超小的Co3O4/Co纳米颗粒。首先，在具有合适孔隙率和孔宽的热震剥离石墨烯网络(EGO)中直接生长ZIF-67纳米晶薄膜。随后，ZIF-67通过在450℃的氮气气氛下针对EGO上的少量剩余氧官能团(大约13个原子%)进行刻蚀。因此，ZIF-67的部分气化和所产生的开放的钴金属中心的氧化产生了高活性的纳米相Co3O4/Co@N-G，质量产率为>；65wt%。合成的Co3O4/Co@N-G-450型催化剂在0.1MKOH溶液中，不需要任何进一步的酸洗或氧化过程，具有较高的起始电位(0.962 V vs.RHE)、半波电位(0.808 V vs.RHE)和极限电流密度(5.2 mA cm(-2))。这些优点可以与商业铂/碳和许多ZIF衍生催化剂相媲美，后者是在长期和复杂的化学处理下合成的。此外，该催化剂还表现出快速的反应动力学，具有主导的4电子反应途径和较高的耐久性。
A facile and controllable low-temperature (450 degrees C) route is reported to produce ultra-small Co3O4/Co nanoparticles in nitrogen-doped hyperporous graphenic networks (Co3O4/Co@N-G-450). Firstly, amonolayer of ZIF-67 nanocrystals is directly grown in thermal-shock exfoliated graphene networks (EGO) of suitable porosity and porewidths. Later, the ZIF-67 is etched by targeting the small concentrations of residual oxygen functionalities on EGO (approximate to 13 atom%) under a nitrogen atmosphere at 450 degrees C. Therefore, the partial gasification of ZIF-67 followed by oxidation of the resultant open cobalt metal centres produces a highly active nanophase of Co3O4/Co@N-G in a mass yield of >65 wt%. The as-synthesised Co3O4/Co@N-G-450 catalyst, without any further acid washing or oxidation process, exhibits an outstanding ORR performance with a high onset (0.962 V vs. RHE) and half-wave (0.808 V vs. RHE) potential as well as limiting current density (5.2 mA cm(-2)) in 0.1 M KOH solution. These merits are comparable to those of commercial Pt/C and many ZIF-derived catalysts, synthesised under extended and complex chemical treatment. Moreover, the catalyst also exhibits fast reaction kinetics with a dominant 4-electron reaction pathway and high durability.