NO oxidation catalysis on copper doped hexagonal phase LaCoO3: a combined experimental and theoretical study

Abstract

Cobalt-based perovskite catalysts showed excellent performance towards NO–NO₂ oxidation. We systematically investigated the influence of different levels of Cu-doping on the catalytic performance of hexagonal phase LaCoO₃ (LaCo_1−xCu_xO₃ (x = 0.1, 0.2, 0.3)) for NO oxidation. The catalytic activities of the oxide catalysts followed the sequence: LaCo_0.9Cu_0.1O₃ > LaCoO₃ > LaCo_0.8Cu_0.2O₃ > LaCo_0.7Cu_0.3O₃ where the highest NO conversion for LaCo_0.9Cu_0.1O₃ was 82% at 310 °C. The relevant structural characterizations were conducted by XRD, BET, FTIR and TEM. The interaction between Co and Cu promoted the conversion of NO to NO₂. Upon increasing the Cu doping content, a decrease of the performance resulted from the generation of isolated CuO on the surface of the oxides, confirmed using H₂-TPR and XPS. Combined with first-principle calculations, we explored the reaction mechanism of NO oxidation on the surface and found that Cu doping would facilitate the reaction by decreasing the energy of oxygen vacancy formation and the NO₂ desorption barrier from Co- or Cu-nitrite.