Enhancing NO Reduction by CO Over NiO/CeO₂ Catalyst by Optimizing the Metal Oxide–Support Interaction

Noble metal catalysts are widely used in three-way catalysts (TWCs) due to their high efficiency, but their scarcity and high cost drive the need for effective, low-cost alternatives. In this work, a series of NiO/CeO₂ catalysts were engineered by modulating the OH content and crystallite size of the CeO₂ support. This approach yielded Ni species ranging from isolated single atoms to small clusters and larger aggregates, with varied NiO/CeO₂ interaction strengths. Evaluation of their performance in NO reduction by CO, CO oxidation, and the water–gas shift reaction revealed that the NiO/CeO₂-300 catalyst, featuring small CeO₂ crystallites and highly dispersed NiO clusters, delivered superior activity for NO reduction and CO oxidation. It was demonstrated that small NiO clusters, due to their efficient CO adsorption and activation, were more active than Ni single atoms. Furthermore, the presence of water was found to influence the catalyst stability, with NiO clusters less stable than single atoms likely due to the hydroxylation effect leading to the formation of Ni(OH)₂. Oxygen storage capacity measurements revealed that performance was governed by a combination of CeO₂ crystallite size and the abundance of NiO/CeO₂ interfaces. These findings demonstrated that the catalytic performance of Ni/CeO₂ systems could be maximized by optimizing the Ni nanostructure and its interaction with CeO₂ support, positioning them as a promising, multifunctional nonprecious alternative for three-way catalysis application.