This study investigates the interactions between CoOₓ and CeO₂ during the oxygen evolution reaction (OER) using operando hard X-ray absorption spectroscopy (hXAS) and ex situ soft XAS (sXAS) combined with electrochemical analysis. The results show that CeO₂ does not act as the active site for OER, but its coupling with CoOₓ modifies the Co and O species at the CoOₓ surface and alters the flat band potential (Efb), leading to more favorable Co oxidation state transformations during OER. The study confirms that the synergy between CoOₓ and CeO₂ enhances OER activity by modifying the electronic structure and surface properties of the composite. Operando hXAS reveals that the Co oxidation state responds to applied potential, while the Ce oxidation state remains unchanged. Ex situ sXAS characterizations show that the interactions between CeO₂ and CoOₓ trigger structural and electronic modifications in the composite. The pH-dependent study indicates that the reaction order of CoOₓ/CeO₂ is lower than that of CoOₓ, suggesting a more concerted proton-electron transfer (CPET) mechanism. The study proposes two reaction pathways: one with decoupled proton transfer as the rate-determining step (RDS) and another with CPET as the RDS. The results demonstrate that CeO₂ modifies the electronic structure and surface properties of CoOₓ, altering the reaction mechanism and improving OER activity without directly participating in the OER reaction. The findings highlight the importance of understanding the electronic and structural interactions between CoOₓ and CeO₂ in enhancing OER performance.This study investigates the interactions between CoOₓ and CeO₂ during the oxygen evolution reaction (OER) using operando hard X-ray absorption spectroscopy (hXAS) and ex situ soft XAS (sXAS) combined with electrochemical analysis. The results show that CeO₂ does not act as the active site for OER, but its coupling with CoOₓ modifies the Co and O species at the CoOₓ surface and alters the flat band potential (Efb), leading to more favorable Co oxidation state transformations during OER. The study confirms that the synergy between CoOₓ and CeO₂ enhances OER activity by modifying the electronic structure and surface properties of the composite. Operando hXAS reveals that the Co oxidation state responds to applied potential, while the Ce oxidation state remains unchanged. Ex situ sXAS characterizations show that the interactions between CeO₂ and CoOₓ trigger structural and electronic modifications in the composite. The pH-dependent study indicates that the reaction order of CoOₓ/CeO₂ is lower than that of CoOₓ, suggesting a more concerted proton-electron transfer (CPET) mechanism. The study proposes two reaction pathways: one with decoupled proton transfer as the rate-determining step (RDS) and another with CPET as the RDS. The results demonstrate that CeO₂ modifies the electronic structure and surface properties of CoOₓ, altering the reaction mechanism and improving OER activity without directly participating in the OER reaction. The findings highlight the importance of understanding the electronic and structural interactions between CoOₓ and CeO₂ in enhancing OER performance.