Low-temperature CO oxidation over Co3O4-based catalysts: Significant promoting effect of Bi2O3 on Co3O4 catalyst

• Reaction rate and TOF of 20 wt.% Bi2O3-Co3O4 were about 4 times to that of pure Co3O4.
• 20 wt.% Bi2O3-Co3O4 could completely convert CO to CO2 at −75 °C for 10 h.
• Low-temperature oxygen activation depended on structural defects of Bi2O3-Co3O4.
• Lower O2 content, higher CO content and presence of CO2 decreased the activity.

The modification of Co3O4 by Bi2O3 significantly enhanced its catalytic performance for CO oxidation. The 20 wt.% Bi2O3-Co3O4 exhibited the best catalytic performance. The results of H2-TPR and CO-TPR revealed that the mobility of oxygen was accelerated greatly and the ability of low-temperature oxygen activation was the crucial factor to improve the catalytic performance. Bi2O3 entered the lattice of Co3O4 caused the structural defect and lattice distortion, which should be the origin of the high O2 activation ability and mobility. Structure-performance correlation demonstrated that the low-temperature oxygen activation was dependent on the defective degree of structure, which was determined by the content of Bi2O3. The catalytic behaviors under different reaction conditions revealed that CO could effectively adsorb on the surface active sites and CO2 could competitively adsorb on the active sites. The ability to supply the active O2 species was suggested to be a key step. The kinetic data showed not only the amount of surface active sites were increased on the surface of Co3O4 but also the catalytic ability of single active site was enhanced greatly.

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