Optimizing Ru Metallene Catalytic Cathodes via Compressive Strain Engineering for an Improved Li-CO₂ Battery

Ru-based catalysts have already shown potential advantages in Li-CO₂ batteries. The strain regulation strategy has been widely used in various catalysts to achieve catalytic activity enhancement. In this study, seven different strained Ru_X metallenes were systemically researched by first-principles calculations, where X = ±6, ±4, ±2, and 0%. The structure and electronic properties of Ru_X metallenes were investigated as well as adsorption energies of reactants, reaction thermodynamics, and electrochemical performance. The results showed that lattice expansion contributed to an upward shift in the d-band center, which enhanced the strength of the CO₂ adsorption on Ru_X. A linear relationship between CO₂ activation and lattice strain was demonstrated by analyzing the bond lengths, bond strengths of C-O, and bond angles of CO₂. Specifically, under tensile strain, the CO₂ activation on Ru_X was gradually improved. Among all Ru_X, Ru_-2 metallene with an appropriate CO₂ adsorption energy exhibited the lowest reaction energy (0.93 eV) for the rate-determining step of Li₂CO₃ and C formation and the lowest overpotential (0.85 V), demonstrating its excellent catalytic performance in Li-CO₂ batteries. This work elucidated the electrochemical mechanism of strain regulation on Ru_X metallenes as cathode catalysts for Li-CO₂ batteries and provided valuable insights for designing metal catalysts with improved catalytic activity.