Cerium-modified Pt/Al2O3 for NH3 synthesis by NO reduction with H2

Highlight • The direct synthesis of NH3 from NO and H2 at atmospheric pressure was studied. • Pt/CeOxAl2O3 showed higher NH3 yield than Pt/Al2O3 and other Pt/Ce containing catalysts. • Moderate Pt-Ce interaction induced metallic Pt well-dispersed on CeOxAl2O3. • Small Pt0 particles appeared to be favorable for initiating NO dissociation. • Brønsted acid sites on CeOx may facilitate NH3 desorption at a lower temperature. The Haber–Bosch process is a mature and proven technology for the commercial production of NH3. However, with the increasing focus on achieving net-zero emissions, alternative technologies have gained interest. This paper proposes an effective catalytic system for synthesizing NH3 directly from NO and H2 at atmospheric pressures. Pt/CeOxAl2O3 synthesized via solvent-deficient precipitation (SDP) showed a much higher NH3 yield compared to conventional Pt/Al2O3 and other Pt/Ce-containing catalysts. Various characterization techniques demonstrated that achieving precise control of the electronic metal-support interaction (EMSI) is crucial for attaining the optimal electronic and geometric structure that balances the decisive factors, Pt oxidation state and Pt dispersion, to enable a high rate of NH3 production from NO and H2. Pt/CeOxAl2O3 possesses abundant metallic Pt nanoclusters that are well dispersed on CeOxAl2O3 due to the moderate Pt-Ce interactions. These small metallic Pt clusters in contact with CeOx turned out to play a critical role in the dissociative adsorption of NO and H2, leading to the formation of the reaction intermediates, the –NH2 species, which contribute to the improved NH3 productivity of Pt/CeOxAl2O3.