Mechanistic Insights on the Low-Temperature Oxidation of CO Catalyzed by Isolated Co Ions in N‑Doped Carbon

Isolated cobalt ions on nitrogen-doped carbon (Co–N–C)
catalyze CO oxidation at temperatures as low as 196 K, but the active
site and mechanism for this reaction remain elusive. In this work,
steady-state CO oxidation around 273 K over Co–N–C revealed
nearly first-order behavior in both CO and O2 as well as
a negative apparent activation energy. Isotopic transient analysis
of the reaction confirmed a rapid turnover frequency and low surface
coverage of adsorbed intermediates leading to CO2 (<10%
of the Co). Results from kinetics experiments combined with quantum
chemical calculations and molecular dynamics simulations are consistent
with a reaction path involving weak adsorption of CO onto Co ions
followed by a low barrier for the CO-assisted activation of weakly
adsorbed O2. This proposed mechanism for dioxygen activation
does not involve a redox cycle with the transition-metal ion and may
be important in other low-temperature catalytic reactions involving
O2.