Development of in situ A-SAXS and XAS Measurements of Pt Catalyst under Controlled Electrochemical Condition Using Channel Flow Electrode Cell

Abstract

Understanding of the structural and the chemical properties of Pt catalysts in polymer electrolyte fuel cells (PEFCs) is necessary to improve the activity for the durability of the catalysts. The small-angle X-ray scattering (SAXS) and the X-ray absorption spectroscopy (XAS) measurements are widely used to investigate these properties. Recently, we developed a measurement system of SAXS and fluorescence-yield (FY)XAS in the same observed area to investigate the structural and the chemical properties of low-concentrated catalysts. [1] As the results, the diameter size, distributions, and chemical state of catalysis were successfully characterized. Our measurement system also found to be easy to combine the electrochemical cell. In this study, we newly developed a channel flow cell to control the electrochemical conditions during SAXS and FYXAS measurement in the same observed area.All experiments were carried out at SPring-8 BL19B2. Electrochemical measurements were conducted using a newly developed channel flow cell. Using the flow system, the electrolyte solution with a controlled temperature was continuously supplied to the cell during the in-situ measurements. A commercial Pt/carbon black catalyst(TEC10E50E, Tanaka Kikinzoku Kogyo) was used as the sample in this experiment. In situ SAXS and FYXAS measurement was conducted while holding the potential at 0.4 V, 1.0 V, and 1.5 V vs. the reversible hydrogen electrode (RHE). For the XAS measurements, the Pt LⅢ edge was used. The ionization chamber and a single-element Ge solid state detector were used to obtain the FYXAS spectra. For the SAXS measurements, the X-ray energy was set to 11.5 keV and 11.55 keV, which are below and near to the Pt LIII absorption edge, respectively. The scattered X-ray was detected using an area detector (PILATUS 2M).As the result, we could estimate the diameter size, distributions, and chemical state of Pt catalysis under controlling the electrochemical conditions. We will discuss the degradation mechanism of the Pt nanoparticle catalyst from both SAXS and FYXAS data.Takeshi Watanabe, et al., ECS 236th I01D-1593, (2019) Atlanta, USA.