Integrating Ozone Pollutant Elimination in N₂ Electrolysis to Produce Nitrate with Reduced Reaction Steps

The synthesis of nitrate by the electrochemical N₂ oxidation reaction (NOR) is currently one of the most promising routes. However, the traditional generation of nitrate depends on the oxidation reaction between N₂ and H₂O (or ·OH), which involves complex reaction steps and intermediates, showing strong competition from oxygen evolution reaction (OER). Here, an effective NOR method is proposed to directly oxidize N₂ by using O₃ as a reactive oxygen source to reduce the reaction step. Electrochemical tests demonstrate that the nitrate yield of Pd-Mn₃O₄/CNT electrocatalyst reaches the milligram level, which is the highest yield reported so far for electrocatalytic NOR. Quantitative characterization is employed to establish a comprehensive set of benchmarks to confirm the intrinsic nature of nitrogen activation and test the O₃-mediated reaction mechanism. Density functional theory (DFT) calculations show that the heterostructure Pd-Mn₃O₄ leads to a strong adsorption preference for N₂ and O₃, which greatly reduces the activation energy barrier for N₂. This accelerates the synthesis of nitrate based on the direct formation mechanism, which reduces energy barriers and the reaction steps, thus increasing the performance of electrocatalytic nitrate production. The techno-economic analysis underscores the promising feasibility and sustainable economic value of the presented method. © 2024 Wiley-VCH GmbH.