Shape Effectof Cu and Ce Species over Modified AttapulgiteCatalysts: Dual Reactivity and Sulfur Resistance in NH₃–SCR and NH₃–SCO

Targeted regulation of the catalytic activity and selectivity is the key to advancing the applications of NH₃–SCO and NH₃–SCR catalysts. Herein, significant differences were found in NH₃ and NO_<i>x</i> removal as well as sulfur resistance of the copper- and cerium-modified attapulgite obtained by different methods. Their structural and chemical characteristics were thus investigated based on various characterization techniques to reveal the key factors affecting catalytic performance. Although influenced by multiple properties, the NH₃ oxidation activity of the catalysts was positively correlated with their proportion and redox ability of asymmetric oxygen vacancies (Cu⁺–O_V–Ce³⁺). The Cu-doped bulk crystalline CeO₂ structure with excessive redox ability promoted byproducts formation and inhibited NO reduction, while the weak interaction between highly dispersed Cu and Ce oxides accompanied by inadequate acid quantity and redox ability restricted the removal of NH₃ and NO. In comparison, good NH₃–SCO and NH₃–SCR performances were exhibited by the CeO₂ clusters-coated highly dispersed CuO_<i>x</i> structure because the formed active nitro compounds could be consumed by NH₃. High sulfur resistance was also achieved from this structure since CuO_<i>x</i> and interface Cu–O–Ce sites were protected. This work provides information for directed synthesis and performance optimization of copper–cerium-based catalysts for NH₃ and NO_<i>x</i> removal.