Surface Geometry-Electronic Structure Synergy in SbN₄-Rich Multidimensional Nanocarbon Boosts Triiodide Reduction

The rational design of electrocatalyst surface structures is of great significance for enhancing catalytic activity by increasing the number of active sites, improving charge-transfer dynamics, and tuning the adsorption behavior of intermediates. Herein, a multidimensional carbon catalyst enriched with atomic antimony coordinated with four nitrogen atoms (i.e., SbN₄) is fabricated for triiodide reduction via controlled chemical unzipping of carbon nanotubes (CNTs) followed by Sb incorporation. This catalyst features a carbon heterostructure comprising CNTs covalently bonded to graphene nanoribbons, along with a tunable surface geometry. Thanks to the unique attributes of the Sb-NDHC-800, it exhibits more than twice the electrochemically active surface area of pristine CNTs (0.98 cm²) and suppresses the inter-component interface. When functioning as an electrocatalyst for triiodide reduction, the Sb-NDHC-800 showcases an ultralow charge-transfer resistance (0.14 Ω cm²) coupled with a short electron lifetime (159.15 µs) on the catalyst-electrolyte interface, exceeding those of the CNTs and DHC-800 counterparts. Theoretical investigations unveil that the tuned electronic structure of the catalyst and SbN₄ geometries synergistically optimize the adsorption process of intermediates, thereby modulating the rate-determining step. This work provides insights for manipulating the surface structure of carbon-based electrocatalysts and elucidating the structure-performance relationships.