A comparative investigation of NdSrCu1-xCoxO4-delta and Sm1.8Ce0.2Cu1-xCoxO4-delta (x: 0-0.4) for NO decomposition

A series of single-phase T-structured NdSrCu1-xCoxO4-delta with oxygen vacancies and T'-structured Sm1.8Ce0.2Cu1-xCoxO4-delta (x: 0-0.4) with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-programmed desorption (NO-TPD). The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCu1-xCoxO4-delta catalysts were of oxygen vacancies whereas the Sm1.8Ce0.2Cu1-xCoxO4-delta ones possessed excessive oxygen (i.e., over-stoichiometfic oxygen); with a rise in Co doping level, the oxygen vacancy density of NdSrCu1-xCoxO4-delta decreased while the over-stoichiometric oxygen amount of Sm1.8Ce0.2Cu1-xCoxO4-delta increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr(-1), and 600-900 degrees C, the catalytic activity of NO decomposition followed the order of NdSrCuO3.702 > NdSrCu0.8Co0.2O3.736 > NdSrCu0.6Co0.4O3.789 > Sm1.8Ce0.2Cu0.6Co0.4O4.187 > Sm1.8Ce0.2Cu0.8Co0.2O4.104 > Sm1.8Ce0.2CuO4.045, in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu3+/Cu2+ redox ability of NdSrCu1-xCoxO4-delta account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.