Regulating ammonia decomposition activity by engineering interface structure of ultrafine ruthenium nanoparticles...

Here we report the construction of ultrafine ruthenium (Ru) nanoparticles anchored on cerium dioxide (CeO₂) supports with different morphologies (nanorods, nanopolyhedrons and nanocubes) tune the metal-support interfacial structure for boosting ammonia decomposition activity. The ultrafine Ru nanoparticles anchored on CeO₂ nanorods (Ru/CeO₂-NR) exhibit the best catalytic activity toward ammonia decomposition, achieving a high hydrogen (H₂) yield rate of 1907 ± 18 mmol_H2 g_Ru^-1 min^-1 at 450 °C and 2368 ± 27 mmol_H2 g_Ru^-1 min^-1 at 500 °C with a gas hourly space velocity (GHSV) of 36,000 mL g_cat.^-1 h^-1, as well as excellent durability over a 100-h test. Comprehensive characterization results demonstrate that, in contrast to CeO₂ nanopolyhedrons enclosed by (100) and (111) facets and nanocubes enclosed by (100) facet, CeO₂ nanorods with dominantly exposed (111) and (110) facets can greatly trigger the electronic metal-support interaction (EMSI), leading to the formation of abundant oxygen vacancies (O_v) and enhanced electron transfer from Ru nanoparticle to CeO₂-NR, consequently creating numerous interfacial active structures (Ru^δ+-O_v-Ce³⁺). These structures not only stabilize the Ru species to avoid sintering, but also endow the catalyst with greatly enhanced ammonia decomposition activity. On the one hand, the interfacial structures enable a largely increased number of basic sites and enhanced electron-donating capacity of Ru/CeO₂-NR, which is beneficial for catalyzing ammonia activation and promoting NN recombination and desorption. On the other hand, the interfacial active sites with positively charged Ru species can effectively weaken the RuH bond strength, facilitating hydrogen desorption and migration at the Ru-CeO₂ interface, thus alleviating hydrogen poisoning and further accelerating reaction kinetics. This study provides insights into metal-support interface engineering for catalyst design in ammonia decomposition.