Department of Chemistry, University of California, Berkeley, California 94720, United States.
Miller Institute for Basic Research in Science, University of California, Berkeley, California 94720, United States.
J Am Chem Soc. 2022 May 25;144(20):8927-8931. doi: 10.1021/jacs.2c03662. Epub 2022 May 16.
Understanding the chemical environment and interparticle dynamics of nanoparticle electrocatalysts under operating conditions offers valuable insights into tuning their activity and selectivity. This is particularly important to the design of Cu nanocatalysts for CO electroreduction due to their dynamic nature under bias. Here, we have developed electrochemical resonant soft X-ray scattering (EC-RSoXS) to probe the chemical identity of active sites during the dynamic structural transformation of Cu nanoparticle (NP) ensembles through 1 μm thick electrolyte. scattering-enhanced X-ray absorption spectroscopy (XAS) serves as a powerful technique to investigate the size-dependent catalyst stability under beam exposure while monitoring the potential-dependent surface structural changes. Small NPs (7 nm) in aqueous electrolyte were found to experience a predominant soft X-ray beam-induced oxidation to CuO despite only sub-second X-ray exposure. In comparison, large NPs (18 nm) showed improved resistivity to beam damage, which allowed the reliable observation of surface CuO electroreduction to metallic Cu. Small-angle X-ray scattering (SAXS) statistically probes the particle-particle interactions of large ensembles of NPs. This study points out the need for rigorous examination of beam effects for X-ray studies on electrocatalysts. The strategy of using EC-RSoXS that combines soft XAS and SAXS can serve as a general approach to simultaneously investigate the chemical environment and interparticle information on nanocatalysts.
了解纳米粒子电催化剂在工作条件下的化学环境和粒子间动力学，为调节其活性和选择性提供了有价值的见解。对于设计用于 CO 电还原的 Cu 纳米催化剂来说，这一点尤为重要，因为它们在偏压下具有动态特性。在这里，我们开发了电化学共振软 X 射线散射（EC-RSoXS），通过 1 μm 厚的电解质来探测 Cu 纳米粒子（NP）团簇在动态结构转变过程中活性位点的化学特性。散射增强 X 射线吸收光谱（XAS）是一种强大的技术，可以在监测潜在依赖表面结构变化的同时，研究在束流暴露下尺寸依赖性催化剂稳定性。尽管仅暴露于亚秒级的 X 射线，但在水溶液电解质中，小 NPs（7nm）经历了主要的软 X 射线束诱导氧化，生成 CuO。相比之下，大 NPs（18nm）显示出对束流损伤的改善电阻，这允许可靠地观察到表面 CuO 电还原为金属 Cu。小角 X 射线散射（SAXS）从统计学上探测了大 NP 团簇的颗粒间相互作用。这项研究指出了在电催化剂的 X 射线研究中需要严格检查束流效应。使用 EC-RSoXS 的策略，结合软 XAS 和 SAXS，可以作为一种通用方法，同时研究纳米催化剂的化学环境和颗粒间信息。
