Applied Thesis

The benchtop XAFS (model: RapidXAFS 2M) facilitates the characterization of molecular-based catalysts, and the scientific research results were published in the form of a paper in the top international journal JACS: Molecular Spacer Strategy Optimizes the Spatial Density of Co Single Atomic Sites.

Single-atom catalysts (SACs) with atom economy and coordination environment accuracy provide a new solution for designing efficient electrocatalysts. In addition to the need for precise local coordination environments, the development of SACs still faces great challenges such as controlled spatially active structures and tolerance under harsh operating conditions. In addition, SACs with high loading tend to have more active sites and excellent catalytic efficiency. However, with the increase of metal loading, the agglomeration of these single-atom sites is unavoidable, which limits the further improvement of the effective active density in SAC. At the same time, high-density single-atom sites are also easy to agglomerate or dissolve during the catalytic process, resulting in the reduction of SAC catalytic activity, and how to maintain the durability of single-atom catalysts under harsh working conditions is still a huge challenge for SAC development.

Figure 1. Molecularly spaced monoatomic catalysts.

(Photo courtesy of J. J. Am. Chem. Soc., DOI: 10.1021/jacs.3c06665）

Starting from the design of molecular-based materials, the LMEC team led by Professor He Chunting of Jiangxi Normal University used a series of different organic anhydrides as spacers to regulate the spatial density of a single Co site in discrete metal phthalocyanine, and designed and synthesized novel molecular-based single-atom catalysts (msSACs), which significantly improved the effective active site density and mass transfer performance, thereby changing the apparent activation energy of the catalysts. Among them, msSACs (CoPc-PM@CNT) linked by trimthalic dianhydride exhibited high mass activity ((1.63±0.01) ×105A·g-1) and TOFbulk (27.66±1.59 s-1at 1.58 V vs RHE), and demonstrated long-term durability at ultra-high current densities of 2.0 A·cm-2 under industrial conditions used for oxygen evolution reactions. The related work was published in the Journal of the American Chemical Society, an internationally renowned chemical journal, with the title of "Optimizing the Spatial Density of Single Co Sites via Molecular Spacing for Facilitating Sustainable Water Oxidation".

图2 (J-G) 三种分子间隔单原子催化剂中Co的K-edge XANES和FT-EXAFS。

（图片来源于J. Am. Chem. Soc., DOI: 10.1021/jacs.3c06665）

XAFS谱学技术是研究单原子催化剂最有效的手段之一，本次实验所有XAFS数据由安徽吸收谱仪器设备有限公司的桌面X射线吸收谱仪测得，型号为RapidXAFS 2M。在本研究中，XAFS一方面表征了三种不同有机酸酐作为间隔分子并没有非常显著改变Co的电子结构和配位环境，证实了分子间隔策略主要优化的是单原子位点的空间密度。该策略超越了传统的电子结构调控，显著地提升了催化剂的有效活性密度、催化传质和催化耐久性，揭示了单原子位点的空间密度是优化催化性能的另一个重要参数。另一方面，研究还通过XAFS谱学技术还证实了CoPc-PM@CNT在OER反应前后Co单原子的配位环境均保持不变，与此类msSACs具有出色的长时间稳定性测试结果相佐证。

该工作为提升SAC的催化活性提供了一种简便的分子增强策略，并为设计高效、稳定、低成本的能源催化剂提供了新的视角。

Fig.3 (a-b) Stability test of each catalyst under different conditions, (c) Stability comparison of catalysts, (d) In-situ CO adsorption FT-IR spectra, (e) In-situ Raman spectra, (f) Optical photographs of the CoPcPM@CNT before and after OER, (g) Electron localization function of CoPc, (h) Binding energy of Co atoms in phthalocyanine (E_b) binding energy to Co (Ec); (i) the radial distribution function of coordination N atoms around Co, and (J-l) K-edge XANES, FT-EXAFS, and wavelet transforms of Co before and after CoPc-PM@CNT OER reaction.

(Photo courtesy of J. J. Am. Chem. Soc., DOI: 10.1021/jacs.3c06665）

Anhui Absorption Spectrum Instrument Equipment Co., Ltd. is a company focusing on the development of X-ray absorption/emission spectrum technology and spectroscopy instruments, providing professional absorption/emission spectrum technology solutions for scientific researchers. The company is led by senior professors from the National Natural Science Foundation of China for Distinguished Young Scholars, based on the background of synchrotron radiation in the field of absorption/emission spectroscopy of more than 10 years of technical research accumulation, the development of standardized desktop X-ray absorption/equipment spectroscopy equipment. The company adheres to the technical pursuit of "bringing XAFS into the laboratory", delves into absorption/emission spectrum technology, carries forward the spirit of craftsmanship and modern scientific innovation, and persistently promotes the research and development of X-ray technology and equipment.

Anhui Absorption Spectrum Instrument Equipment Co., Ltd. has successfully developed and launched four different configurations of desktop XAFS to the market, the model is: RapidXAFS 500K; RapidXAFS 1M, RapidXAFS 1M plus；RapidXAFS 2M, RapidXAFS 2M plus。

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