Experimental And Mechanistic Studies On Catalytic Oxidation Of CO By La-based Perovskite

CO emitted from the processes of fossil fuel utilization is harmful to the human health and environment.CO oxidation into CO₂ is regarded as an efficient way to remove CO.The commercial CO oxidation catalysts are well-known to be Pt,Rh,Pd.However,noble metal catalysts are expensive and susceptible to sintering.To solve these problems of noble catalysts,this work developed cost-effective catalysts for CO oxidation.A series of LaBO₃（B=Co,Mn,Fe）and B site-doped La Co_1-xB_xO₃（B=Ni、Zn、Cr）perovskite materials were developed as the catalysts for CO oxidation.The results indicate that Co atom on the catalyst surface mainly exists in the form of Co³⁺.The prepared LaCoO₃and La Co_0.9Ni_0.1O₃ perovskites have a small particle size less than 10μm.Some fine particles exist on the catalyst surface.The experimental results show that LaCoO₃ and La Co_0.9Ni_0.1O₃ show excellent CO oxidation performance and long-term stability.The reaction mechanism of CO oxidation over LaCoO₃ catalyst was investigated through density functional theory（DFT）calculations.The calculation results indicate that the adsorption of reactants（CO and O₂）over LaCoO₃ catalyst is controlled by the chemisorption mechanism.The reaction pathway of CO oxidation on the LaCoO₃ surface contains three steps:CO+*→CO*,CO*+O₂*→CO₂+O*and CO+O*→CO₂*.The rate-limiting step of CO oxidation reaction on LaCoO₃ is CO*+O₂*→CO₂+O*,which has an activation energy（66.08 k J/mol）and reaction heat（-58.44 k J/mol）.The catalytic reaction mechanism of CO oxidation by O₂ over La Co_0.9Ni_0.1O₃ catalyst was examined by using the DFT calculations.Chemisorption mechanism is responsible for the adsorption behavior of CO and O₂ on La Co_1-xNi_xO₃ catalyst.The CO*+O₂*→CO₂+O*is the rate-limiting step because of its relatively higher energy barrier（17.20 k J/mol）.