Oxalate Catalytic Pathway Over Fault‐Twinned PdRh Bimetallene Enables Ultrastable Mg‐CO 2 Batteries

The reversibility of Mg‐CO 2 batteries relies on stabilizing the oxalate pathway, yet conventional catalysts, such as noble metal catalyst, transition metal catalyst, and redox mediator, tend to over‐stabilize oxalate intermediates, impeding their desorption and leading to carbonate formation, challenging the stability of Mg‐CO 2 batteries. In this work, we propose a binding‐weakening electronic modulation strategy that balances CO 2 activation and MgC 2 O 4 release for greatly enhancing the reversibility of Mg‐CO 2 batteries. We demonstrate that the fault‐twinned PdRh bimetallene, where Rh incorporation downshifts the Pd d ‐band center for weakening oxalate adsorption and Rh‐derived conduction states enhance CO 2 activation, can well catalyze the reversible CO 2 conversion. Meanwhile, strain fields from abundant stacking faults create undercoordinated Pd sites that facilitate CO 2 → C 2 O 4 2− conversion. This dual regulation stabilizes the oxalate pathway that previous catalysts could not sustain for achieving ultrastable cycling over 700 h with minimal polarization (1.10 V discharge, 1.21 V charge), which represents a benchmark for both durability and energy efficiency among Mg‐CO 2 batteries. The work establishes a new mechanistic foundation for rational pathway control in multivalent CO 2 electrochemistry.