Cerium Oxide with Specific Surface Oxygen Vacancy and Facet for Nitrate Synthesis through Electrocatalytic Nitrogen Oxidation

Recently, the green and sustainable synthesis of nitric acid (HNO₃) through the electrochemical nitrogen oxidation reaction (NOR) has attracted significant attention. Developing high-efficiency electrocatalysts to overcome the challenges caused by the chemical inertness of N₂ and the slow, 10-electron transfer kinetics is highly desirable. In this work, we investigated the NOR performance of cerium oxide (CeO₂), which is known for its excellent oxygen storage and release capabilities. The concentration of oxygen vacancies and the morphology with different specific surface areas and exposed crystal facets have a significant influence on NOR activity. The hollow nanosphere with primarily exposed {111} facets exhibits the highest oxygen vacancy content (35.07%) and the largest surface area (101.26 m²/g), leading to an optimal NO₃^- yield of 383.06 μmol·h^-1·g_cat^-1 with a Faradic efficiency (FE) of 5.17% at 1.7 V vs RHE. <i>In situ</i> Fourier transform infrared (FTIR) spectroscopy confirmed the formation of *NO₂, *NO, and NO₃^- species on the CeO₂ hollow nanosphere electrode during the NOR. Theoretical calculations were also performed to confirm the effects of oxygen vacancies and the {111} crystal plane on CeO₂ hollow nanospheres, leading to excellent NOR catalytic activity of CeO₂ materials.