Si Wenfang, Xie Qianjie, Zhang Ruiyi, Wang Zheng, Shen Yehua, Uyama Hiroshi
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, No. 1, Xuefu Road, 710127 Xi'an, Shaanxi, China.
College of Food Science and Engineering, Northwest University, No. 229 Taibai North Road, 710069 Xi'an, Shaanxi, China.
Dalton Trans. 2022 Aug 2;51(30):11363-11371. doi: 10.1039/d2dt01718k.
Metal-organic frameworks (MOFs) have been widely used as precursors to derive carbon-based electrocatalysts for the oxygen reduction reaction (ORR) due to their high porosity and tunable chemical composition/structure. However, the influence of MOF type on the structure and further ORR activity of derived metal-free carbon catalysts is still elusive. In the present work, a series of different Zn-based MOFs were employed as precursors to explore this issue. Meanwhile, prepare N-doped metal-free carbon catalysts were prepared for the ORR under the activation of sacrificial urea (which is effective to enhance the ORR activity of carbon-based catalysts). By analyzing the intermediates during pyrolysis, it is found that the decisive role of MOF types on the doped N and the morphology of derived carbon catalysts was played by the Zn coordination environment of MOFs and its reactivity with the decomposition intermediate of urea. Although the structure and porosity of derived carbon catalysts from different MOFs are very different, they all showed superior ORR activity and Zn-air battery performance up to 20 wt% Pt/C benchmark catalysts. From the above analyses, the combination of urea and compounded Zn is also a promising activation method for the preparation of highly-efficient metal-free carbon electrocatalysts.
金属有机框架材料（MOFs）因其高孔隙率和可调节的化学组成/结构，已被广泛用作制备用于氧还原反应（ORR）的碳基电催化剂的前驱体。然而，MOF类型对衍生的无金属碳催化剂的结构及进一步的ORR活性的影响仍不明确。在本工作中，一系列不同的锌基金属有机框架材料被用作前驱体来探究这个问题。同时，在牺牲尿素的活化作用下（这对提高碳基催化剂的ORR活性有效）制备了用于ORR的氮掺杂无金属碳催化剂。通过分析热解过程中的中间体，发现MOF类型对掺杂氮及衍生碳催化剂形貌的决定性作用是由MOF的锌配位环境及其与尿素分解中间体的反应性所发挥的。尽管来自不同MOF的衍生碳催化剂的结构和孔隙率差异很大，但它们都表现出优于20 wt% Pt/C基准催化剂的ORR活性和锌空气电池性能。从上述分析可知，尿素和复合锌的组合也是制备高效无金属碳电催化剂的一种有前景的活化方法。
