[CO-SCR Performance and Mechanism over Co₃O₄ Catalysts]

Nitrogen oxide (NO) is an important precursor for many air pollution problems such as fine particulate matter and ground-level ozone. Because air pollution levels increase daily, it is important to control NO emissions from industrial boiler flue gas. A series of different Co₃O₄ catalysts was prepared in this study by different methods. The effects of the preparation methods on selective catalytic reduction of NO by CO (CO-SCR) were investigated. The catalysts were characterized by BET, XRD, HR-TEM, and Raman. The results show that the Co₃O₄-S catalyst, prepared by solid grinding with cobalt sulfate as the precursor, had better CO-SCR activity and H₂O resistance and that Co₃O₄-C, prepared by solid grinding with cobalt acetate as the precursor, showed excellent H₂O resistance. The NO oxidation results showed that better NO oxidation activity over the catalysts is an important reason for the improved CO-SCR activity. The Raman results indicate that more Co²⁺ ions appeared on the surface of Co₃O₄-S, which benefited the formation of oxygen vacancies. The H₂-TPR results showed better redox property of the Co₃O₄-S catalyst. The HR-TEM results shoes that the (111) and (220) crystal planes were exposed mainly on Co₃O₄-S and Co₃O₄-O and that more (220) crystal planes are conducive to improved reaction.