In-Situ Raman Spectroscopy of CO2 Reduction on CeO2-Supported Catalysts

The catalytic reduction of CO₂ through dry reforming of methane (DRM) represents a crucial pathway for carbon utilization and sustainable syngas production, yet its efficiency is inherently tied to the redox behavior of the catalysts. Among the key factors influencing catalytic performance, the generation and evolution of oxygen vacancies play a pivotal role, as these defects facilitate CO₂ activation and bond cleavage. Despite their significance, the precise mechanisms governing temperature-driven oxygen vacancy formation and regeneration under reaction conditions remain insufficiently understood.

In this study, we employ in-situ Raman spectroscopy to track the real-time evolution of oxygen vacancies as a function of temperature in CeO₂-supported catalysts during DRM. Firstly, we initiate our investigation with bare CeO₂ nanorods (NR) in an inert Ar environment, probing their intrinsic Ce⁴⁺ to Ce³⁺ reduction behavior at elevated temperature. Subsequently, we extend our study to a reactive CH₄ + CO₂ atmosphere, examining how the combined effects of temperature and reaction gases drive oxygen vacancy formation in an active DRM environment. Finally, we explore the role of Ni or Ru-based CeO₂ NR-supported catalysts, assessing how metal-oxide interactions influence oxygen mobility and redox dynamics during the reaction. The findings provide crucial insights into tailoring oxygen vacancy behavior to maximize DRM efficiency and long-term catalyst stability.