A comparative investigation of NdSrCu 1− xCo xO 4−δ and Sm 1.8Ce 0.2Cu 1− xCo xO 4−δ ( x: 0–0.4) for NO decomposition

Abstract

A series of single-phase T-structured NdSrCu 1− x Co x O 4−δ with oxygen vacancies and T′-structured Sm 1.8Ce 0.2Cu 1− x Co x O 4−δ ( 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 NdSrCu 1− x Co x O 4−δ catalysts were of oxygen vacancies whereas the Sm 1.8Ce 0.2Cu 1− x Co x O 4−δ ones possessed excessive oxygen (i.e., over-stoichiometric oxygen); with a rise in Co doping level, the oxygen vacancy density of NdSrCu 1− x Co x O 4−δ decreased while the over-stoichiometric oxygen amount of Sm 1.8Ce 0.2Cu 1− x Co x O 4−δ 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 NdSrCuO 3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr −1, and 600–900°C, the catalytic activity of NO decomposition followed the order of NdSrCuO 3.702 > NdSrCu 0.8Co 0.2O 3.736 > NdSrCu 0.6Co 0.4O 3.789 > Sm 1.8Ce 0.2Cu 0.6Co 0.4O 4.187 > Sm 1.8Ce 0.2Cu 0.8Co 0.2O 4.104 > Sm 1.8Ce 0.2CuO 4.045, 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 Cu 3+/Cu 2+ redox ability of NdSrCu 1− x Co x O 4−δ account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.