Recovering High-Temperature EXAFS Despite Debye–Waller Damping by Modulation-Excitation XAS

Extended X-ray absorption fine structure (EXAFS) analysis at elevated temperature is limited by Debye–Waller damping, which suppresses high-k oscillations and narrows the usable fitting range. Here, we demonstrate that modulation-excitation X-ray absorption spectroscopy (ME-XAS) combined with phase-sensitive detection (PSD) recovers analyzable EXAFS from PtFe/Al2O3 under alternating H2/O2 gas atmosphere. At both the Pt-LIII and Fe-K edges, reversible redox dynamics were isolated while suppressing the spectral noise. Even at temperatures up to 700 °C, the reconstructed spectra retain high-k oscillations. These oscillations are otherwise buried by the noise in the raw data, yielding a 2–3-fold improvement in the signal-to-noise ratio. This workflow extends operando EXAFS into temperature regimes where conventional measurements are often restricted to X-ray absorption near-edge structure (XANES) analysis.