Perovskite Oxide as A New Platform for Efficient Electrocatalytic Nitrogen Oxidation

Electrocatalytic nitrogen oxidation reaction (NOR) offers an efficient and sustainable approach for conversion of widespread nitrogen (N2) into high-value-added nitrate (NO3-) under mild conditions, representing a promising alternative to the traditional approach that involves harsh Haber-Bosch and Ostwald oxidation processes. Unfortunately, due to the weak absorption/activation of N2 and the competitive oxygen evolution reaction, the kinetics of NOR process is extremely sluggish accompanied with low Faradaic efficiencies and NO3- yield rates. In this work, an oxygen-vacancy-enriched perovskite oxide with nonstoichiometric ratio of strontium and ruthenium (denoted as Sr0.9RuO3) was synthesized and explored as NOR electrocatalyst, which can exhibit a high Faradaic efficiency (38.6 %) with a high NO3- yield rate (17.9 mu mol mg-1 h-1). The experimental results show that the amount of oxygen vacancies in Sr0.9RuO3 is greatly higher than that of SrRuO3, following the same trend as their NOR performance. Theoretical simulations unravel that the presence of oxygen vacancies in the Sr0.9RuO3 can render a decreased thermodynamic barrier toward the oxidation of *N2 to *N2OH at the rate-determining step, leading to its enhanced NOR performance. An oxygen-vacancy-enriched Sr and Ru perovskite oxide is constructed by modulating the Sr-site deficiency, thus exhibiting high Faradaic efficiency (38.6 %) and high NO3- yield rate (17.9 mu mol mg-1 h-1) in the electrocatalytic nitrogen oxidation reaction (NOR). The Ru active sites along with their adjacent oxygen vacancies in the perovskite oxide enhance the adsorption/activation of N2 molecules and decrease the thermodynamic barrier towards NOR.image

Automated summary

In this study, an oxygen-vacancy-enriched perovskite oxide was synthesized and explored as an electrocatalyst for the NOR process. The results showed high Faradaic efficiency and yield rate, which were correlated with the amount of oxygen vacancies. Theoretical simulations revealed that the presence of oxygen vacancies can decrease the thermodynamic barrier for the NOR reaction.