Decoupling Adsorption and Dissociation of Sulfur on Single-Atom Alloys for Robust CO/CO₂ Methanation

The industrial synthesis of substitute natural gas via CO/CO₂ methanation is severely hampered by the irreversible deactivation of nickel catalysts by trace sulfur impurities. Overcoming this challenge is difficult because the electronic properties that make nickel active also make it prone to strong sulfur bonding, creating a fundamental scaling relation. Here, we report a robust sulfur-tolerant catalyst constructed by atomically dispersing ruthenium into a nickel lattice, which breaks this limitation. By leveraging the electronegativity difference between Ru and Ni, we induce a directed charge transfer that functionally decouples sulfur adsorption from the catalytic turnover. Combining in situ spectroscopy and density functional theory, we reveal that electron-rich Ru single atoms act as deep thermodynamic traps for H₂S but energetically inhibit its dissociation into poisoning sulfide species. This decoy effect leaves the adjacent electron-deficient Ni ensemble sites protected and free to drive the methanation reaction. Consequently, the catalyst exhibits exceptional stability in 10 ppm H₂S stream conditions that rapidly deactivate monometallic counterparts during both CO and CO₂ methanation. This work demonstrates a generalizable electronic immunization strategy to design durable catalysts by spatially separating toxicant adsorption sites from active centers.