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 H 2 S. 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 N 5 square-pyramidal coordination geometry, create a stable, efficient, and selective catalyst for H 2 S-to-S 8 oxidation. Unlike the typical Ni–N 4 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 S 8 product and the monatomic Ni active center facilitate product desorption, preserving active site integrity. Consequently, the Ni-NC catalyst demonstrates high H 2 S-to-S 8 performance (354 g S kg cat –1 h –1 ), long-term stability (>100 h), and resistance to common impurities like CO, CO 2, and H 2 O from biomass or blast furnace gas under high GHSV (30 L g –1 h –1 ) and high H 2 S concentration (10000 ppm). This work offers insights into designing robust SACs for poisoning reagent removal catalysis and suggests potential applications in the desulfurization industry.