Unraveling the Enhanced Activity and Effect of H₂O/O₂ on the Low-Temperature NO Reduction by CO over Ag-Modified Porous Co₃O₄ Nanosheets

Abstract

The cobalt-based catalysts were broadly investigated in NO reduction with CO; however, further development is limited by the poor low-temperature catalytic activity and H2O/O2 resistance. Herein, a series of Ag-doped Co3O4 porous nanosheets (xAgCo) were synthesized and applied into NO reduction with CO reaction. The formation of more oxygen vacancies of xAgCo catalysts was promoted by the weakened Co–O bond strength; therefore, the redox properties and oxygen mobility were enhanced. The xAgCo catalysts reached superior catalytic activities compared with Co3O4. Especially, 0.02AgCo exhibited the optimal catalytic performance, achieving the lowest apparent active energy (E a = 34 kJ mol–1). The enhanced catalytic activity of xAgCo could be attributed to the optimized CO adsorption, promoted NO dissociation, and the formation of *NCO species. The 5 vol % H2O enhanced the NO conversion through promoting the decomposition of accumulated carbonate species. Meanwhile, the O2 or 10 vol % H2O inhibited the NO conversion due to the coverage of active sites and the competitive adsorption/reaction.