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.