Room temperature CO oxidation catalyzed by NiO particles on mesoporous SiO₂ prepared via atomic layer deposition: Influence of pre-annealing temperature on catalytic activity

We prepared NiO nanoparticles on mesoporous SiO₂ using atomic layer deposition and additionally annealed the prepared samples at four different temperatures (300-750 °C) under dry air. NiO nanoparticles had lateral sizes less than ∼2 nm up to 600 °C, whereas annealing at a higher temperature (750 °C) resulted in a significant agglomeration of NiO, with the formation of 30 nm-sized particles. Annealing at a higher temperature resulted in a reduction in carbon impurities in the annealing temperature range of 300-600 °C. Among the four samples annealed at different temperatures, the 450 °C-annealed sample showed the highest CO oxidation activity at room temperature. CO oxidation reactivity of this sample initially decreased with reaction time; however, the deactivation became less pronounced over time, with maintenance of 60% of the initial activity of this catalyst after 680 min. Furthermore, 450 °C-annealing of used catalyst resulted in full recovery of the initial CO oxidation reactivity. These results suggest that ALD followed by annealing is a promising strategy for the fabrication of highly efficient and stable catalysts consisting of nanoparticles incorporated in the mesopores of a high-surface area support.