Ambient Electrosynthesis of Ammonia on Core-Shell Structure Au@CeO2 Catalyst: Contribution of Oxygen Vacancies in CeO2.

Electrosynthesis of NH3 from N2 reduction reaction (NRR) at ambient conditions has been regarded as a promising technology to replace the industrial energy and capital intensive Haber-Bosch process. Here we report a room-temperature spontaneous redox approach to fabricate core-shell structure Au@CeO2 composite with Au nanoparticle sizes below ~10 nm and loading amount of 3.6 wt.% for the NRR. The results demonstrate that the as-synthesized Au@CeO2 possesses a surface area of 40.7 m2 g-1 and porous structure, as electrocatalyst exhibiting high NRR activity with a NH3 yield rate of 28.2 μg h-1 cm-2 (10.6 μg h-1 mg-1cat., 235.0 μg h-1 mg-1Au) and a faradaic efficiency (FE) of 9.50% at -0.4 V vs. reversible hydrogen electrode (RHE) in 0.01 M H2SO4 electrolyte. The characterization results reveal the presence of rich oxygen vacancies in the formed CeO2 nanoparticles shell of Au@CeO2, favourable for N2 adsorption and activation for the NRR. This has been further verified by our theoretical calculations results. The abundant oxygen vacancies in CeO2 nanoparticles shell combined with Au nanoparticles core of Au@CeO2 are electrocatalytically active sites for the NRR, synergistically enhancing the conversion performance of N2 to NH3.