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 Co3S4 as a model system, density functional theory (DFT) calculations reveal that the adjusted d-band and p-band centers of Co3S4 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 Li2CO3, 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.