A Homo-Triatomic Molybdenum Cluster Catalyst Enables Synergistic Optimization of Multi-Step Sulfur Reduction...

The isolated single-active sites of single-atom catalysts (SACs) often suffer from simultaneously maintaining the optimal adsorption states of multiple lithium polysulfide intermediates in sulfur redox reactions of Li-S batteries. Herein, we report a homo-triatomic molybdenum cluster catalyst with Mo₃-O₃N₃ motifs embedded within a carbon matrix (Mo₃/ONC) that addresses this challenge. The Mo₃-O₃N₃ motifs with a triangular configuration feature multi-active sites and interatomic synergies, which can flexibly adjust the corresponding Mo─S pathway according to different intermediate sulfur species, thereby making the adsorption strength of all species favorable. Meanwhile, the optimized Mo─S interactions can induce more electrons to transfer from the intermediate sulfur species to the Mo₃-O₃N₃ catalytic sites, thus weakening the S─S bond and remarkably reducing the energy barriers for the sulfur conversion. Besides, the electrochemical and in situ spectroscopic experiments disclose that the sulfur redox kinetics on Mo₃/ONC is significantly improved compared to the Mo-single-atom catalyst (Mo₁/ONC) counterpart. As thus, the as-designed Mo₃/ONC catalyst renders the Li-S battery with a large rate capability of 661.2 mAh g^-1 and a capacity decay as low as 0.027% per cycle at 10 C for 1200 cycles. This work provides a new perspective on the fundamental design principles of triatomic catalysts for improving the Li-S performance.