X-ray absorption spectroscopy (XAS) is a powerful technique that provides information about the electronic and local geometric structural properties of newly developed electrocatalysts, especially when it is performed under operating conditions (i.e., operando). However, the large amounts of catalyst typically needed to achieve sufficiently high spectral quality and temporal resolution can result in working electrodes of several micrometers in thickness. This can in turn lead to an inhomogeneous potential distribution across the electrode, delamination, and/or incomplete utilization of the catalyst layer (CL), as well as to the (partial) shielding of the CL with electrochemically evolved bubbles trapped within its pores. These limitations can be tackled by performing such spectrochemical measurements with low-loaded (and thus thin) electrodes, which call for the acquisition of XAS spectra in fluorescence mode and using an X-ray beam incidence angle of ≤0.1° with regards to the working electrode’s substrate plane in a grazing-incidence (GI) configuration. Thus, in this work, we introduce a new spectroelectrochemical flow cell that allows one to perform such measurements in this GI mode and verify its functionality by tracking the potential-induced formation of palladium hydride (PdH_x) in a Pd nanoparticle-based electrocatalyst. A time resolution of 10 s per spectrum was achieved with a very low Pd-loading of only 30 μg_Pd/cm². Moreover, the implementation of an ion-conductive membrane to separate the working- and counter-electrode compartments enables the quantification of reaction products, which, in the case of gaseous species, can be detected in a time-resolved manner by means of mass spectrometry. Chiefly, this allows us to determine the electrocatalytic activity and selectivity of a given material in the same cell configuration used for the spectroscopic measurements and assures a reliable comparison among the results derived from both techniques.

中文翻译：

---

用于低负载电极原位掠入射 X 射线吸收光谱研究的电化学池


X 射线吸收光谱 （XAS） 是一种强大的技术，可提供有关新开发的电催化剂的电子和局部几何结构特性的信息，尤其是在操作条件（即操作）下进行时。然而，实现足够高的光谱质量和时间分辨率通常需要大量的催化剂，这可能导致工作电极的厚度为几微米。这反过来又会导致电极上的电位分布不均匀、分层和/或催化剂层 （CL） 的不完全利用，以及 CL 的（部分）屏蔽被困在其孔内的电化学逸出气泡。这些限制可以通过使用低负载（因此很薄）电极进行此类光谱化学测量来解决，这需要在荧光模式下采集 XAS 光谱，并在掠入射 （GI） 配置中使用相对于工作电极衬底平面的 ≤0.1° 的 X 射线束入射角。因此，在这项工作中，我们引入了一种新的光谱电化学流动池，它允许人们在这种 GI 模式下进行此类测量，并通过跟踪基于 Pd 纳米颗粒的电催化剂中氢化钯 （PdH_x） 的电位诱导形成来验证其功能。每个谱图的时间分辨率为 10 s，Pd负载量非常低，仅为 30 μg_Pd/cm²。此外，使用离子导电膜来分隔工作电极和反电极隔室，可以定量反应产物，在气态物质的情况下，可以通过质谱法以时间分辨方式检测反应产物。 主要是，这使我们能够在用于光谱测量的相同单元配置中确定给定材料的电催化活性和选择性，并确保对两种技术得出的结果进行可靠的比较。