Energy Band Engineering Guided Design of Bidirectional Catalyst for Reversible Li-CO₂ Batteries

Li-CO₂ batteries arouse great interest in the context of carbon neutralization, but their practicability is severely hindered by the sluggish CO₂ redox reaction kinetics at the cathode, which brings about formidable challenges such as high overpotential and low Coulombic efficiency. For the complex multi-electron transfer process, the design of catalysts at the molecular or atomic level and the understanding of the relationship between electron state and performance are essential for the CO₂ redox. However, little attention is paid to it. In this work, using Co₃ S₄ as a model system, density functional theory (DFT) calculations reveal that the adjusted d-band and p-band centers of Co₃ S₄ with the introduction of Cu and sulfur vacancies are hybridized between CO₂ and Li species, respectively, which is conducive to the adsorption of reactants and the decomposition of Li₂ CO₃ , and the experimental results further verify the effectiveness of energy band engineering. As a result, a highly efficient bidirectional catalyst is produced and shows an ultra-small voltage gap of 0.73 V and marvelous Coulombic efficiency of 92.6%, surpassing those of previous catalysts under similar conditions. This work presents an effective catalyst design and affords new insight into the high-performance cathode catalyst materials for Li-CO₂ batteries.