Recent advances in NO reduction with CO over copper-based catalysts: reaction mechanisms, optimization strategies, and anti-inactivation measures

Abstract

The selective catalytic reduction of NO with CO (CO-SCR) is a promising strategy to reduce the emission of nitrogen oxides (NOx) and carbon monoxide (CO) from motor vehicle exhaust and industrial flue gases (from sintering, coking, and so on). As one of the transition metals, copper-based catalysts have been extensively studied for NO reduction with CO. At present, composite oxides (Cu–CeOx, Cu–MnOx, etc.,), supported Cu based catalysts (Cu/Ce-MnOx, Cu/Ce-FeOx, etc.,), nanomaterials (nano-hollow spinel, nanosheets, etc.,), and Cu-based catalysts derived from MOFs and LDHs exhibited the most superior performance with NO conversion generally reaching above 90% around 200 °C. In this study, some optimization strategies were proposed in designing catalysts with high catalytic activity, such as selecting supports with superior performance, using LDHs and MOFs precursors, optimizing morphology and crystal plane, metals doping, and reduction pretreatment. In the reaction pathway, NO dissociation is considered to be the key step for NO + CO reaction. Also, copper valence state, surface oxygen vacancies (SOVs), and surface synergistic oxygen vacancies (SSOVs) play a critical role in NO reduction with CO. Moreover, anti-inactivation measures in the presence of H2O, SO2, and O2 were proposed. Based on the above discussion, some suggestions were proposed for future research work that efforts should be made. Hopefully, valuable information can be provided in this review for realizing the industrial application of CO-SCR catalysts.