When Photoelectrons\nMeet Gas Molecules: Determining\nthe Role of Inelastic Scattering in Ambient Pressure X‑ray\nPhotoelectron Spectroscopy

Inelastic photoelectron\nscattering (IPES) by gas molecules,\na critical\nphenomenon observed in ambient pressure X-ray photoelectron spectroscopy\n(APXPS), complicates spectral interpretation due to kinetic energy\nloss in the primary spectrum and the appearance of additional features\nat higher binding energies. In this study, we systematically investigate\nIPES in various gas environments using APXPS, providing detailed insights\ninto interactions between photoelectrons emitted from solid surfaces\nand surrounding gas molecules. Core-level XPS spectra of Au, Ag, Zn,\nand Cu metals were recorded over a wide kinetic energy range in the\npresence of CO<sub>2</sub>, N<sub>2</sub>, Ar, and H<sub>2</sub> gases,\ndemonstrating the universal nature of IPES across different systems.\nAdditionally, we analyzed spectra of scattering effects induced by\ngas-phase interactions without metal solids. In two reported CO<sub>2</sub>-reduction systems (p-GaN/Au/Cu and p-Si/TaO<sub><i>x</i></sub>/Cu), we elucidated that IPES is independent of the composition,\nstructure, or size of the solid materials. Using metal foil platforms,\nwe further developed an analytical model to extract electron excitation\ncross sections of gas molecules. These findings enhance our understanding\nof IPES mechanisms and enable the predictions of IPES structures in\nother solid–gas systems, providing a valuable reference for\nfuture APXPS studies and improving the accuracy of spectral analysis\nin gas-rich catalytic interfaces.