Cauliflower-like MnCeO_x catalyst for low-temperature NH₃-SCR coupled with CO oxidation: Balancing surface redox-acidity and promoting nitrate decomposition via CO

Efficient low-temperature removal of NO_x and CO is highly desirable for overcoming the complexity and high cost associated with conventional multi-step industrial emission control systems. With their favorable redox and surface properties, MnCeO_x catalysts show promising potential for the efficient and synergistic removal of pollutants. However, excessive nitrates accumulation can block active sites and hinder performance on MnCeO_x. In this work, morphology engineering was employed to balance redox activity, optimize acidic sites distribution, and boost catalytic performance. The synthesized cauliflower-like MnCeO_x catalyst (C-MCO) exhibited the highest efficiency for both NH₃-SCR and CO oxidation reactions. Characterization analysis revealed that C-MCO with special structure exhibited relatively low redox activity and abundant acid sites, facilitating the conversion of nitrates accumulated on its surface. In situ DRIFTS analysis further confirmed that bidentate bridging nitrates on the C-MCO catalyst showed higher reactivity than those on other morphologies. Additionally, it also exhibited more abundant Brønsted and Lewis acid sites, which could enhance the reaction between surface nitrates and adsorbed NH₃. Moreover, the CO possessed certain reactivity toward the bidentate bridging nitrate on C-MCO, slightly enhancing their consumption and transformation under CO feeding. This study advances the understanding of MnCeO_x catalyst design for NH₃-SCR coupled CO oxidation and reveals the key surface reaction mechanisms responsible for their high efficiency.