Leveraging Soft Acid‐Base Interactions Alters the Pathway for Electrochemical Nitrogen Oxidation to Nitrate with High Faradaic Efficiency

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-12, Vol.20 (51), p.e2406718-n/a
• Main Authors: Singh, Robin, Biswas, Ashmita, Barman, Narad, Iqbal, Muzaffar, Thapa, Ranjit, Dey, Ramendra Sundar
• Format: Article
• Language: English
• Subjects: Acidic oxides; Chemical synthesis; Electrocatalysts; electrochemical nitrogen oxidation reaction; in situ ATR‐IR; nitrate electrosynthesis; Nitrates; Nitrogen; ostwald process; Ostwald ripening; Oxidation; Oxygen evolution reactions; oxygen vacancy; Tin dioxide; Tin oxides
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202406718

Electrocatalytic nitrogen oxidation reaction (N2OR) offers a sustainable alternative to the conventional methods such as the Haber–Bosch and Ostwald oxidation processes for converting nitrogen (N2) into high‐value‐added nitrate (NO3−) under mild conditions. However, the concurrent oxygen evolution reaction (OER) and inefficient N2 absorption/activation led to slow N2OR kinetics, resulting in low Faradaic efficiencies and NO3− yield rates. This study explored oxygen‐vacancy induced tin oxide (SnO2‐Ov) as an efficient N2OR electrocatalyst, achieving an impressive Faradaic efficiency (FE) of 54.2% and a notable NO3− yield rate (22.05 µg h−1 mgcat−1) at 1.7 V versus reversible hydrogen electrode (RHE) in 0.1 m Na2SO4. Experimental results indicate that SnO2‐Ov possesses substantially more oxygen vacancies than SnO2, correlating with enhanced N2OR performance. Computational findings suggest that the superior performance of SnO2‐Ov at a relatively low overpotential is due to reduced thermodynamic barrier for the oxidation of *N2 to *N2OH during the rate‐determining step, making this step energetically favorable than the oxygen adsorption step for OER. This work demonstrates the feasibility of ambient nitrate synthesis on the soft acidic Sn active site and introduces a new approach for rational catalyst design. The study explores the introduction of oxygen vacancy in tin oxide, wherein charge redistribution partakes along the active site modulating the site‐selective adsorption energies of N2 and OH‐ and improving the electrochemical nitrogen oxidation reaction to nitric acid.