Ambient Electrosynthesis of Ammonia on a Core–Shell‐Structured Au@CeO₂ Catalyst: Contribution of Oxygen Vacancies in CeO₂

Abstract

Electrosynthesis of NH₃ through the N₂ reduction reaction (NRR) under ambient conditions is regarded as promising technology to replace the industrial energy- and capital-intensive Haber-Bosch process. Herein, a room-temperature spontaneous redox approach to fabricate a core-shell-structured Au@CeO₂ composite, with Au nanoparticle sizes below about 10 nm and a loading amount of 3.6 wt %, is reported for the NRR. The results demonstrate that as-synthesized Au@CeO₂ possesses a surface area of 40.7 m² g^-1 and a porous structure. As an electrocatalyst, it exhibits high NRR activity, with an NH₃ yield rate of 28.2 μg h^-1 cm^-2 (10.6 μg h^-1 mg^-1 _cat. , 293.8 μg h^-1 mg^-1 _Au ) and a faradaic efficiency of 9.50 % at -0.4 V versus a reversible hydrogen electrode in 0.01 m H₂ SO₄ electrolyte. The characterization results reveal the presence of rich oxygen vacancies in the CeO₂ nanoparticle shell of Au@CeO₂ ; these are favorable for N₂ adsorption and activation for the NRR. This has been further verified by theoretical calculations. The abundant oxygen vacancies in the CeO₂ nanoparticle shell, combined with the Au nanoparticle core of Au@CeO₂ , are electrocatalytically active sites for the NRR, and thus, synergistically enhance the conversion of N₂ into NH₃ .