Operando X-ray Characterizations of Fuel Cell Catalysts

Capturing/identifying the active state of (electro)catalysts under operating conditions, namely operando, is the ultimate objective of (electro)catalyst characterization, serving both to unravel complex reaction mechanisms and advance (electro)catalyst development. Operando insights advance our understanding of the correlations between electrochemical tests and device-level performance. Operando characterization of electrocatalysts is challenging due to the complexity of electrochemical devices and the limitations of instrumentation.
Here, we present our progress on the development of operando characterization techniques for electrochemical devices using synchrotron-based X-ray methods, including X-ray absorption spectroscopy (XAS) and small/wide-angle X-ray scattering (S/WAXS), as illustrated in Fig. 1. Operando X-ray characterizations enable real-time capture of the chemical state, coordination environments, and structures of catalysts under operating conditions. Using these operando methods, we investigated Mn-based spinel oxides oxygen reduction reaction (ORR) catalysts and elucidated the origin of the discrepancy between electrochemical half-cell measurements and anion-exchange membrane fuel cell (AEMFC) performance. The active states of electrocatalyst active centers and their structural evolution under AEMFC operating conditions were successfully captured.
Our results demonstrate the power of operando characterizations in delivering unique insights and accelerating electrocatalyst development. More broadly, this approach is readily extendable to other electrochemical processes, including CO2 reduction and ammonia oxidation, enabling the rational design of electrochemical conversion devices with higher efficiency and durability.