High-performance electrocatalytic nitrate reduction into ammonia using a chitosan regulated Co nanocatalyst†

Abstract

The electrocatalytic nitrate reduction reaction (NtrRR) offers an attractive alternative to the Haber–Bosch process for ambient ammonia (NH₃) production. Herein, a chitosan regulated Co nanoparticle catalyst (Co-NPs/CC) is designed as an electrocatalyst for achieving highly efficient NtrRR catalysis, and it exhibits a high NH₃ yield rate of 9181.7 ± 60.9 μg h⁻¹ cm⁻² at −1.2 V (vs. RHE) and a high faradaic efficiency (FE) of 88.7 ± 4.0% at −1.0 V (vs. RHE) in a 0.1 M K₂SO₄ + 0.1 M KNO₃ electrolyte under ambient conditions. The Co-NPs/CC also exhibited an outstanding performance with a selectivity of 99.5 ± 0.2% for NH₃ synthesis. The obtained NH₄⁺ was also qualitatively determined by colorimetric and ¹H NMR methods. ¹⁵N isotopic labelling identifies that the N atom of the formed NH₃ originates from nitrate. Using in situ attenuated total reflection surface-enhanced infrared adsorption spectroscopy (ATR-SEIRAS) and different electrochemical mass spectrometry (DEMS) measurements, the electrocatalytic NtrRR mechanism was verified. This work presents a novel strategy for designing non-noble metal NtrRR electrocatalysts with exposed favorable active sites.