Jia Yining, Huang Rong, Qi Ruijuan
Key Laboratory of Polar Materials and Devices, Ministry of Education, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China.
Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.
Nanomaterials (Basel). 2022 Apr 20;12(9):1416. doi: 10.3390/nano12091416.
Numerous efforts have been devoted to realizing the high loading and full utilization of single-atom catalysts (SACs). As one of the representative methods, atom migration-trapping (AMT) is a top-down strategy that converts a certain volume of metal nanoparticles (NPs) or metal-based precursors into mobile metal species at high temperature, which can then be trapped by suitable supports. In this study, high-loading iron single atoms anchored onto carbon matrix/g-CN hybrid supports were obtained through a single-atom migration-trapping method based on metal-organic framework (MOF) pyrolysis. It is confirmed, by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), that the Fe(acac) precursor is reduced to Fe single atoms (SAs), which are not only anchored onto the original N-doped carbon (NC), but also onto g-CN, with an Fe-N coordination bond. Further electrochemical results reveal that Fe-CN-0.075 possesses a better half-wave potential of 0.846 V and onset potential of 0.96 V compared to Fe-N-C, the product obtained after pyrolysis of Fe(acac)@ZIF-8. As opposed to SAs prepared by the pyrolysis process only, SAs prepared by AMT are commonly anchored onto the surface of the supports, which is a simple and effective way to make full use of the source metal and prepare SACs with higher exposing active sites.
人们为实现单原子催化剂（SACs）的高负载量和充分利用付出了诸多努力。作为代表性方法之一，原子迁移捕获（AMT）是一种自上而下的策略，它在高温下将一定体积的金属纳米颗粒（NPs）或金属基前驱体转化为可移动的金属物种，然后这些物种可被合适的载体捕获。在本研究中，通过基于金属有机框架（MOF）热解的单原子迁移捕获方法，获得了锚定在碳基质/g-CN混合载体上的高负载量铁单原子。通过高角度环形暗场扫描透射电子显微镜（HAADF-STEM）、X射线吸收近边结构（XANES）和扩展X射线吸收精细结构（EXAFS）证实，Fe(acac)前驱体被还原为铁单原子（SAs），这些单原子不仅锚定在原始的氮掺杂碳（NC）上，还通过Fe-N配位键锚定在g-CN上。进一步的电化学结果表明，与Fe(acac)@ZIF-8热解后得到的产物Fe-N-C相比，Fe-CN-0.075具有更好的半波电位0.846 V和起始电位0.96 V。与仅通过热解过程制备的单原子不同，通过AMT制备的单原子通常锚定在载体表面，这是充分利用源金属并制备具有更高暴露活性位点的SACs的一种简单有效方法。
