Influence of Mn/Ce ratio on the physicochemical properties and catalytic performance of graphene supported MnOx-CeO₂ oxides for NH₃-SCR at low temperature

Highlights: • MnOx-CeO₂(8:1)/GR exhibited high catalytic activity and improved resistance to H₂O and SO₂. • The uniform distribution and the interaction between manganese and cerium oxide species are conductive to protect surface active sites. • The formation of MnOx-CeO₂ solid solution and more oxygen vacancies could promote the oxidation of NO into NO₂. - Abstract: A series of MnOx-CeO₂/graphene catalysts prepared by a hydrothermal method with different molar ratios of Mn/Ce active components were loaded on graphene for low-temperature SCR of NOx with NH₃. Experimental results indicated that these catalysts exhibited excellent low-temperature SCR activities and strong resistance against SO₂. The characterization results indicated that manganese and cerium oxides dispersed on the surface of graphene uniformly, and that manganese oxide existed in different forms of crystallinities (MnO, Mn₃O₄, and MnO₂). The MnOx-CeO₂(8:1)/GR displayed superior activity, high N₂ selectivity, and good resistance to H₂O and SO₂, which would be very attractive for the application in controlling NOx emission from flue gas. Its excellent catalytic performance and SO₂ tolerance at low temperature were attributed to the high content of manganese with high oxidation valence, increased chemisorbed oxygen on the surface, more active sites, and the strong interaction between MnOx-CeO₂ active sites and graphene support.