H2O2-mediated electrosynthesis of nitrate from air

Renewable electricity-driven electrochemical nitrogen oxidation is a promising alternative to traditional Haber-Bosch and Ostwald processes to directly synthesize nitrate from nitrogen. However, its efficiency is hindered by strong competition from the oxygen evolution reaction in aqueous environments, along with a deficiency in standardized testing protocols. Here we present an efficient approach for nitrogen oxidation, substituting the oxygen evolution reaction with hydroxyl radicals (<middle dot>OH) generated through hydrogen peroxide decomposition to serve as an active oxygen source. Electrochemical tests demonstrate that the nitrogen oxidation, facilitated by <middle dot>OH, can achieve a Faradaic efficiency of 25.6% and a nitrate yield of 8.3 nmol s(-1) cm(-2). Furthermore, we employed in situ electrochemical mass spectrometry, gas-phase infrared and electron paramagnetic resonance spectroscopy to establish a comprehensive set of benchmarks to confirm the authenticity of nitrogen activation and to examine the reaction mechanism mediated by <middle dot>OH. Techno-economic analysis underscores the promising feasibility and sustainable economic value of the presented method.