Synergistic Dual d ‐Band Engineering at the Ru‐N 4 /MXene Interface for High‐Efficiency and Long‐Lived Li–CO 2 Batteries

ABSTRACT The cyclability of Li–CO 2 batteries is fundamentally limited by the sluggish kinetics of Li 2 CO 3 formation and decomposition. In this work, we develop a Ru‑N 4 single‑atom catalyst anchored on MXene (MX‑Ru SA ), in which the atomic interface establishes a synergistic dual d ‑band center to overcome this kinetic constraint. The N coordination modifies the electronic state of Ru, upshifting its d ‐band center to strengthen intermediate adsorption and steer the growth of vertically aligned Li 2 CO 3 nanosheets that facilitate efficient electron and ion transport. Meanwhile, the presence of Ru‐N 4 sites modulates the electronic structure of the MXene support, optimizing the d ‐band center of Ti, which weakens the Li─O bonds in Li 2 CO 3 and significantly reduces its decomposition barrier. As a result, the Li–CO 2 battery with MX‑Ru SA delivers a high discharge capacity of 14757 mA h g −1 , along with an ultralow charging overpotential of 0.56 V and a long cycle life over 3000 h at 100 mA g −1 . This work demonstrates interfacial dual d ‑band synergy as a promising design principle toward high‑performance catalysts for metal‐gas battery systems.