Y-induced oxygen vacancy engineering and local electronic reconstruction for enhanced ammonia decomposition over Ni1Ce1-xYxOα

Le résumé fourni par la source

• Ni 1 Ce 0.5 Y 0.5 O α exhibits the highest activity, achieving 84% NH 3 conversion at 550 °C. • Y doping leads to the generation of more O v in Ni 1 Ce 0.5 Y 0.5 O α . • Y modifies the electronic structure of the catalyst to facilitate N association. • Y doping maintains the stability of the surface O v at high temperatures. Ammonia decomposition is considered an ideal carbon-free pathway to hydrogen production. However, the limited catalytic activity of non-noble metal catalysts for ammonia decomposition remains a major barrier to their industrial deployment. Here, we developed a modulation strategy that simultaneously tunes the structural and electronic properties of Ni-based catalysts to improve their catalytic performance. Yttrium (Y) was introduced as a dopant via a citrate sol–gel auto-combustion method into Ni/CeO 2 , enabling compositionally controlled Y incorporation over the electron–defect landscape. This method yields a well-defined Ni 1 Ce 1-x Y x O α structure, in which Y 3+ , with its different ionic radius from Ce 4+ , is homogeneously incorporated into the CeO 2 lattice to form a solid solution, generating abundant and stable surface oxygen vacancies and modulating the electronic environment of Ni active sites. Among the Ni 1 Ce 1-x Y x O α catalysts prepared, Ni 1 Ce 0.5 Y 0.5 O α exhibits the highest activity, achieving 84% NH 3 conversion at 550 °C (GHSV = 30000 mL·g cat -1 ·h −1 ) and a H 2 production rate of 1687 ± 14 mmol·g cat -1 ·h −1 , along with robust thermal stability. The calculated results suggest that Y doping decreases the formation energy of oxygen vacancies and perturbs the local electronic environment, which enhances electron transfer to the Ni active sites, increasing Ni valence electron density. N associative desorption as the rate-determining step (RDS) was determined at Ni 1 Ce 0.5 Y 0.5 O α , in which the electronic modulation, in synergy with surface oxygen vacancies, reduces the energy barrier for N association by 0.21 eV and renders this step thermodynamically favorable. This work demonstrates that the strategic use of Y as a dual-functional promoter enhances the catalytic activity in ammonia decomposition.

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