Diatomic Catalysts for Aqueous Zinc-Iodine Batteries: Mechanistic Insights and Design Strategies

There has been a growing interest in developing catalysts to enable the reversible iodine conversion reaction for high-performance aqueous zinc-iodine batteries (AZIBs). While diatomic catalysts (DACs) have demonstrated superior performance in various catalytic reactions due to their ability to facilitate synergistic charge interactions, their application in AZIBs remains unexplored. Herein, we present, for the first time, a DAC comprising Mn-Zn dual atoms anchored on a nitrogen-doped carbon matrix (MnZn-NC) for iodine loading, resulting in a high-performance AZIB with a capacity of 224 mAh g^-1 at 1 A g^-1 and remarkable cycling stability over 320,000 cycles. The electron hopping along the Mn-N-Zn bridge is stimulated via a spin exchange mechanism. This process broadens the Mn 3d_xy band width and enhances the metallic character of the catalyst, thus facilitating charge transfer between the catalysts and reaction intermediates. Additionally, the increased electron occupancy within the d-orbital of Zn elevates Zn's d-band center, thereby enhancing chemical interactions between MnZn-NC and I-based species. Furthermore, our mechanism demonstrates potential applicability to other Metal-Zn-NC DACs with spin-polarized atoms. Our work elucidates a clear mechanistic understanding of diatomic catalysts and provides new insights into catalyst design for AZIBs.