Electron‐Localized RuNi Nanosheet Assemblies Enable Low‐Overpotential Mg‐CO ₂ Battery

ABSTRACT Mg‐CO 2 battery is emerging as a promising energy storage system that simultaneously converts CO 2 into value‐added products. However, its practical application is hindered by formation thermodynamically stable and electrically insulating discharge product MgCO 3 , which severely limits energy efficiency of Mg‐CO 2 battery. Herein, we report an electron‐localized Ru 61 Ni 39 nanosheet assembly catalyst that overcomes these limitations by precisely engineering the surface electronic structure for achieving precise tuning of product from MgCO 3 to MgC 2 O 4 of Mg‐CO 2 battery. We demonstrate that electron transfer from Ni to Ru creates the localized electron at the Ru sites, weakening MgC 2 O 4 binding and suppressing its conversion to MgCO 3 , thereby enabling reversible formation and decomposition of MgC 2 O 4 and mitigating cathode passivation. The Mg‐CO 2 battery incorporating the electron‐localized Ru 61 Ni 39 nanosheet assembly catalyst achieves an ultralow charge overpotential of 0.07 V and a record‐high energy conversion efficiency of 94.1%, with the stable cycling for over 580 h. In situ electrochemical spectroscopy and theoretical studies reveal that the electron‐localized between Ru and Ni stabilizes the product intermediates (C 2 O 4 2− ) and prevents the MgC 2 O 4 conversion to MgCO 3 .