Size-Dependent Effects of Ru Nanoparticles on Li-CO2 Batteries

Li-CO₂ batteries capture and convert CO₂ into a valuable energy storage medium, promoting both energy storage and environmental sustainability. While Ru-based catalysts exhibit exceptional catalytic activity and are widely deployed in Li-CO₂ batteries, the Ru nanoparticle size effects on electrolysis remains underexplored. Herein, we synthesized Ru nanoparticles ranging from ∼1.1 to ∼7.4 nm to unveil the size-dependent activity in Li-CO₂ batteries. As Ru size decreases, the d-band center of Ru is identified upshifted toward the Fermi level, and the Gibbs energy change for the rate-determining step during charge is lowered. The binding energy of C═O and Li–O is notably reduced, confirming that a strong interaction between small Ru and Li₂CO₃ can destabilize Li₂CO₃ and facilitate its decomposition. Furthermore, small Ru nanoparticles can alleviate Li₂CO₃ accumulation on cathodes. This work provides insight and guidance for catalyst design and optimization in Li-CO₂ batteries, which can be extended to other battery systems involving solid product formation and decomposition.