Winzely Maximilian, Clark Adam H, Diercks Justus S, Safonova Olga, Rüttimann Peter, Leidinger Paul M, Phadke Sumant, Schmidt Thomas J, Herranz Juan
Paul Scherrer Institut, Center for Energy and Environmental Science, CH-5232 Villigen, Switzerland.
Paul Scherrer Institut, Center for Photon Science, CH-5232 Villigen, Switzerland.
Anal Chem. 2024 Dec 31;96(52):20454-20464. doi: 10.1021/acs.analchem.4c04233. Epub 2024 Dec 17.
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., ). 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) 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/cm. 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.
X射线吸收光谱法（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性质的信息，特别是在操作条件下进行测量时（即 ）。然而，为了获得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厚度达到几微米。这进而可能导致电极上电位分布不均匀、分层和/或催化剂层（CL）利用不完全，以及CL被捕获在其孔隙中的电化学析出气泡（部分）屏蔽。通过使用低负载（因此较薄）的电极进行此类光谱化学测量，可以解决这些限制，这需要在荧光模式下采集XAS光谱，并在掠入射（GI）配置中相对于工作电极的基底平面使用≤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通池，它允许在这种GI模式下进行此类测量，并通过跟踪基于钯纳米颗粒的电催化剂中电位诱导的氢化钯（PdH）形成来验证其功能。在仅30μg/cm的极低钯负载量下，每个光谱实现了10秒的时间分辨率。此外，采用离子导电膜分隔工作电极和对电极室能够对反应产物进行定量，对于气态物质，可以通过质谱以时间分辨的方式进行检测。主要地，这使我们能够在用于光谱测量的相同电池配置中确定给定材料的电催化活性和选择性，并确保两种技术所得结果之间的可靠比较。
