A synchrotron radiation-based experimental setup for in-situ study of direct borohydride fuel cell cathode

Background: Identifying the natures of the active sites in the catalysts is one of the key issues for the catalytic mechanism research. However, no accurate conclusions regarding to the nature of the electrocatalytic site that active in oxygen reduction reaction (ORR) can be extracted based merely on ex-situ data of the dry material. Purpose: A new kind of in-situ experimental setup based on BL15U1 in Shanghai Synchrotron Radiation Facility (SSRF) is designed to study the catalytic mechanism deeply by in situ characterization which is expected to be the most direct and necessary method. Methods: The in-situ X-ray Diffraction (XRD) and Fluorescent X-ray Absorption Near Edge Structure (XANES) measurements were performed for the cathode catalyst (polypyrrole modified carbon supported cobalt hydroxide) of DBFC on BL15U1 in SSRF. Results: A new phase was formed during DBFC discharging, and the valence state varieties of Co atoms in cathode were recorded. Conclusions: Part of the Co²⁺ transformation to Co³⁺ to form Co²⁺/Co³⁺ balance during the catalytic reaction, resulting in the formation of a new chemical phase. It is confirmed that, by the preliminary analysis, this setup can provide real time evidence which can be used to research the ORR catalytic mechanism of the direct borohydride fuel cell cathode catalyst. (authors)