Nanoscale Co-based catalysts for low-temperature CO oxidation

Nanoscale Co-based carbon materials were prepared by simple thermolysis of a Co-containing metal–organic framework (MOF), ZIF-67, at different temperatures and their catalytic performance for low-temperature CO oxidation was evaluated. Co/C-600, which was obtained from ZIF-67 pyrolysis at 600 °C, exhibited high catalytic activity for CO oxidation even at a temperature as low as −30 °C. The calculated apparent activation energy of CO oxidation over the Co/C-600 catalyst was around 22 kJ mol−1. Moreover, the CO conversion remained unchanged at 100% after 24 h time on stream at room temperature, demonstrating good long-term stability. The results obtained after the introduction of moisture (H2O content, ~500 ppm) into the feed gas showed that the Co/C catalyst was tolerant of wet conditions, showing an unusual temperature-dependent catalytic behavior. Intensive investigation of the catalytic performance led to the conclusion that adsorption of H2O molecules in the micropores of the catalyst caused this unusual catalytic behavior. This finding was supported by in situ FTIR spectroscopic experiments under both dry and wet conditions. Moreover, the catalytic activity of the Co/C material for CO oxidation could be fully recovered by mild heating treatment.