Atomically dispersed Ce species adjacent to Ni nanoparticles as hydrogen scavengers for efficient catalytic ammonia decomposition.

Abstract

CeO₂ serves as an essential support or promoter for catalysts in ammonia decomposition, especially those based on Ni, yet its direct contribution to promoting NH₃ activation and H₂ desorption has rarely been understood. Here, we prepare a Ni-Ce-Al trinary catalyst with high-loading (66.5 wt%) Ni nanoparticles. Connected by the Al₂O₃ framework, these Ni nanoparticles are surrounded by abundant atomically dispersed Ce species consisting of Ce single atoms and clusters. The activity-stability trade-off induced by intrinsic Ni sintering on the CeO₂ support is overcome, achieving a high H₂ production rate of 324.0 mmol g_cat^-1 min^-1 at 600 °C. The promoting effect of CeO₂ has been elucidated, originating from the alleviation of hydrogen poisoning. Atomically dispersed Ce species with high hydrogen affinity serve as scavengers for adsorbed H atoms (H^*). The strong tendency to form Ce³⁺‒OH groups facilitates the migration of H^* from Ni nanoparticles to the oxide, releasing poisoned Ni sites and promoting NH₃ activation.