High-Performance Ru Metallene Cathode via 2D MXenes Interface Tailoring in Li-CO2 Batteries

Abstract

Li-CO₂ batteries were known for exceptional theoretical energy density of 1876 W h/kg, which were an integrated system for energy storage and CO₂ fixation. The cathode catalysts played a crucial role in addressing the slow reaction kinetics during the charge and discharge processes in Li-CO₂ batteries. The Ru-based catalyst had attracted considerable research attention, but its large-scale application was hindered by its catalytic performance dependence on support properties and high cost. This study introduced a series of composite structure that Ru(001) atomic layer loaded on hexagonal MXenes substrate, finely tuned the electronic structure of surface Ru atoms by strain and ligand effects. Ru/M₂X displayed a wide range of tunable d band center from -1.39 eV to -1.04 eV. Among 11 MXene supports, Ru atom layer located on V₂C exhibited reduced rate-determining step of 1.03 eV and remarkably low total overpotential of 0.79 V, making it an excellent bifunctional catalyst. Furthermore, φ = $\phi ={\epsilon }_{d_{{\mathrm{x}}^2-{\mathrm{y}}^2}}/x$$\phi ={\epsilon }_{d_{{\mathrm{x}}^2-{\mathrm{y}}^2}}/x$ (the ratio of band center for $d_{{\mathrm{x}}^2-{\mathrm{y}}^2}$$d_{{\mathrm{x}}^2-{\mathrm{y}}^2}$ to electronegativity χ) serves as a descriptor that demonstrates a strong linear relationship with total overpotential. These findings offered a design strategy and selection criteria for the structural design of Ru-based materials.