Stable and Active Axial N-Coordinated Ni Single-Atom Catalyst for Catalytic Desulfurization

The strong interactions arising from stable coordination structures in single-atom catalysts (SACs) may confer certain antideactivation properties in the presence of poisons like CO and H2S. However, such strong bonding often limits reactivity in ongoing catalytic reactions. This study introduces a Ni-NC SAC where single-atom active sites, stabilized by pyridine nuclei in a classical N5 square-pyramidal coordination geometry, create a stable, efficient, and selective catalyst for H2S-to-S8 oxidation. Unlike the typical Ni–N4 square-planar geometry, the addition of a fifth axial pyridinic N donor enhances the electron density of the monatomic Ni site, reducing the activation energy of intermediate HS* species from 2.62 to 1.12 eV. Weak interactions between the S8 product and the monatomic Ni active center facilitate product desorption, preserving active site integrity. Consequently, the Ni-NC catalyst demonstrates high H2S-to-S8 performance (354 gS kgcat–1 h–1), long-term stability (>100 h), and resistance to common impurities like CO, CO2, and H2O from biomass or blast furnace gas under high GHSV (30 L g–1 h–1) and high H2S concentration (10000 ppm). This work offers insights into designing robust SACs for poisoning reagent removal catalysis and suggests potential applications in the desulfurization industry.