Defects Dynamic in Photo‐Excited CeO ₂ and their Influence on CO ₂ Photoreduction

Abstract Defects play a crucial role in shaping the efficiency and performance of semiconductor‐based technologies. Under illumination, the interaction between photo‐excited charge carriers and defect states in the semiconductor can significantly influence the response of devices and catalysts. Here, an X‐ray photoelectron spectroscopy study conducted under light excitation is presented to track exciton generation and its interaction with defects in CeO ₂ , a widely used metal‐oxide support in (photo) catalysis. The light intensity‐dependent measurements reveal that photo‐excited electrons in CeO ₂ can effectively reduce Ce ⁴⁺ to Ce ³⁺ . Surface‐enhanced Raman spectroscopy further highlights the critical role of Ce ³⁺ states in governing charge and energy transport across the CeO ₂ ‐molecule interface. Finally, how these photo‐induced states (Ce ³⁺ ) can be leveraged is demonstrated to control the selectivity in the photocatalytic CO ₂ reduction reaction, dramatically influencing the yields of CO, CH ₄ , and H ₂ .