Electron-Enriched Ni Clusters Interfaced with CeO2 for Efficient H2 Production from NH3 Decomposition

Abstract

Catalytic NH₃ decomposition has drawn growing interest in constructing the NH₃-based hydrogen economy. Ni catalysts show great potential in this reaction but suffer from low atom utilization efficiency and unclear structure–activity relationship. Here, atomic layer deposition was used to grow Ni clusters on CeO₂ nanorods to create a highly active catalyst for NH₃ decomposition, which outperforms the conventional Ni nanoparticle catalysts and the synthesized Ni single-atom catalyst. The distinct catalytic behaviors of Ni clusters and Ni single atoms were systematically investigated. It is revealed that the interfacial confinement effect induces a strong electronic interaction between Ni clusters and CeO₂, wherein abundant O_v-Ce³⁺ sites are formed in the vicinity of Ni clusters, resulting in interfacial electron-enriched Ni^δ− sites. These Ni^δ− sites bind to N adatoms moderately, favoring N–H bond cleavage and nitrogen desorption (the rate-determining step), which is the origin of the high activity. In contrast, ionic Ni single atoms diffusing into the CeO₂ lattice display a much lower activity since strongly bound N adatoms block the active sites and retard the overall rate. This work provides a deep understanding of Ni-catalyzed NH₃ decomposition and paves the way for designing high-performance metal catalysts for other structure-sensitive reactions.