This study investigates the intercalation of copper (Cu) ions into Ti3C2Tx MXene and its impact on its electronic and electrochemical properties. Using X-ray absorption spectroscopy (XAS) and ab initio molecular dynamics (AIMD), the researchers observed that Cu2+ ions undergo partial reduction upon intercalation into the MXene. In situ XAS revealed changes in the oxidation states of intercalated Cu ions and Ti atoms during charging. The pseudocapacitive response of Cu-MXene is attributed to the redox of both the Cu intercalant and Ti3C2Tx host. Despite highly reducing potentials, Cu ions inside the MXene show excellent stability against full reduction upon charging. The findings demonstrate how electronic coupling between Cu ions and Ti3C2Tx modifies the electronic and electrochemical properties of the MXene, providing a framework for the rational design and utilization of transition metal intercalants to tune the properties of MXenes for various electrochemical applications.This study investigates the intercalation of copper (Cu) ions into Ti3C2Tx MXene and its impact on its electronic and electrochemical properties. Using X-ray absorption spectroscopy (XAS) and ab initio molecular dynamics (AIMD), the researchers observed that Cu2+ ions undergo partial reduction upon intercalation into the MXene. In situ XAS revealed changes in the oxidation states of intercalated Cu ions and Ti atoms during charging. The pseudocapacitive response of Cu-MXene is attributed to the redox of both the Cu intercalant and Ti3C2Tx host. Despite highly reducing potentials, Cu ions inside the MXene show excellent stability against full reduction upon charging. The findings demonstrate how electronic coupling between Cu ions and Ti3C2Tx modifies the electronic and electrochemical properties of the MXene, providing a framework for the rational design and utilization of transition metal intercalants to tune the properties of MXenes for various electrochemical applications.