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

Graphical Room at the active site : A room-temperature redox approach is used to prepare a composite core–shell-structured Au@CeO 2 electrocatalyst (see figure) composed of small gold nanoparticles (<10 nm) and rich oxygen vacancies in CeO 2 nanoparticles to synergistically boost the electrocatalytic activity toward the N 2 reduction reaction (NRR) to NH 3 . Electrosynthesis of NH 3 through the N 2 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@CeO 2 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@CeO 2 possesses a surface area of 40.7 m 2 g −1 and a porous structure. As an electrocatalyst, it exhibits high NRR activity, with an NH 3 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 H 2 SO 4 electrolyte. The characterization results reveal the presence of rich oxygen vacancies in the CeO 2 nanoparticle shell of Au@CeO 2 ; these are favorable for N 2 adsorption and activation for the NRR. This has been further verified by theoretical calculations. The abundant oxygen vacancies in the CeO 2 nanoparticle shell, combined with the Au nanoparticle core of Au@CeO 2 , are electrocatalytically active sites for the NRR, and thus, synergistically enhance the conversion of N 2 into NH 3 .