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 (HNO 3 ) 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 N 2 and the slow, 10-electron transfer kinetics is highly desirable. In this work, we investigated the NOR performance of cerium oxide (CeO 2 ), 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 m 2 /g), leading to an optimal NO 3 – yield of 383.06 μmol·h –1 ·g cat –1 with a Faradic efficiency (FE) of 5.17% at 1.7 V vs RHE. In situ Fourier transform infrared (FTIR) spectroscopy confirmed the formation of *NO 2, *NO, and NO 3 – species on the CeO 2 hollow nanosphere electrode during the NOR. Theoretical calculations were also performed to confirm the effects of oxygen vacancies and the {111} crystal plane on CeO 2 hollow nanospheres, leading to excellent NOR catalytic activity of CeO 2 materials.