Scientists from the Catalan Institute of Nanoscience and Nanotechnology (ICN2) and the Catalan Institute for Energy Research (IREC) used the EM02-METCAM, the electron microscope dedicated to materials science at the new JEMCA center, to study the atomic structure of catalytic materials that are crucial for the functioning of a new type of battery. The images obtained with the EM02-METCAM were key to resolving the atomic structure of the nanoparticles of spinel catalysts. The results have been published in the 'Journal of the American Chemical Society'.
After only six months from the inauguration of the Joint Electron Microscopy Center at ALBA (JEMCA), this marvel of technology is already feeding published research. In fact, the first paper including data and images obtained with the EM02-METCAM microscope has just been published in the Journal of the American Chemical Society (JACS). And this is set to be the first of many. Recently, the other microscope of the JEMCA center (EM01-Cryo-TEM) also published its first results, proving the outstanding performance of both instruments and its great value for the scientific community.
The EM02-METCAM (a monochromated and double aberration corrected scanning transmission electron microscope, for the technology-savvies) allows atomic-resolution inspection of the crystalline structure and electronic configuration of materials, something that goes far beyond the mere analysis of their composition. The possibility to study material structures at very small scale is greatly sought after by researchers, not only with the aim of achieving a deeper understanding of chemical and physical phenomena, but also that of engineering novel materials with “custom” (so to speak) properties.
The EM02-METCAM, whose Platform is coordinated by the Catalan Institute of Nanoscience and Nanotechnology (ICN2), is the first microscope of its kind in Spain. With great expectations from the scientists involved in the JEMCA, this powerful tool was immediately put to the test and has gone through a period of commissioning that it has successfully completed.
One of the first studies on which the remarkable properties of the METCAM were tested is the investigation of a family of catalysts –i.e., structures that promote and accelerate certain chemical reactions— that are relevant for application in new types of batteries. Nanoparticles of these catalysts, named “spinel” catalysts for their specific crystal structure, were synthesized by the Functional Nanomaterials group, headed by ICREA Prof. Andreu Cabot, at the Catalonia Institute for Energy Research (IREC) and analysed at the METCAM by researchers from the ICN2 Advanced Electron Nanoscopy Group led by ICREA Prof. Jordi Arbiol. The goal was to shed light on how the geometric configuration, composition, and electronic structure of the nanoparticles under study influence the mechanisms of catalysis.
The new kid on the block proved to be up to the task. The METCAM microscope could easily achieve spatial resolutions below 50 pm –where 1 picometers (pm) is one trillionth of a meter—when operated at an energy of 300 keV and spatial resolutions below 100 pm when operated at 60 keV. The energy resolution achieved at 60 keV when using the monochromator was 13.6 meV.
The atomic-resolution data provided by the METCAM enabled the authors to better understand how these spinel catalysts facilitate reactions and, above all else, to underpin the role of each of their component in the conversion process of polysulfides taking place during charge and discharge of lithium-sulfur batteries. The images obtained with the new equipment were key to resolving the atomic structure of the spinel catalysts. Furthermore, electron energy loss spectroscopy (EELS) information (also provided by the METCAM) was used to study the electronic structure of the surface of the nanoparticles.
Thanks to all these extremely valuable data –combined with the results of other experimental analysis techniques, electrochemical and battery tests, as well as theoretical calculations— the researchers could formulate a comprehensive description of the dependence of spinel catalysts on geometric configuration in the sulfur reduction reaction process. A profound knowledge of the material structure and of the involved reactions represents an essential basis for the rational development of improved catalysts and, ultimately, better-performing batteries.
“The METCAM microscope has definitely exceeded our expectations, consistently achieving resolutions superior to those stated in its technical specifications,” comments Prof. Jordi Arbiol, who is the Scientific Coordinator of the METCAM Platform and co-author of the publication. “The versatility of the multiple detector options, which can be seamlessly combined for both imaging and spectroscopy, empowers us to gain profound insights into materials.” A wealth of achievements and great results are confidently expected for this technological gem, as well as the other cutting-edge microscopes and equipment that constitutes the JEMCA.
Reference Identifying the Role of the Cationic Geometric Configuration in Spinel Catalysts for Polysulfide Conversion in Sodium–Sulfur Batteries
Chao Yue Zhang, Xuan Lu, Xu Han, Jing Yu, Chaoqi Zhang, Chen Huang, Lluís Balcells, Alba Garzón Manjón, Jordi Jacas Biendicho, Junshan Li, Jordi Arbiol, Gengzhi Sun, Jin Yuan Zhou, and Andreu Cabot