Ambient ammonia production via electrocatalytic nitrate reduction catalyzed by a flower-like CuCo2O4 electrocatalyst

Abstract

The electrochemical nitrate reduction reaction (NtRR) under ambient conditions is regarded as a potential approach to achieve NH₃ production, which currently heavily relies on the Haber–Bosch process at the cost of a huge amount of energy and the massive production of CO₂. Herein, a flower-like CuCo₂O₄ spinel was synthesized via a two-step urea-assisted hydrothermal treatment and calcination process. When used as the electrocatalyst for the NtRR, the as-synthesized CuCo₂O₄ spinel exhibits a high electrocatalytic activity, affording a high NH₃ yield rate of 48.8 μg h⁻¹ cm⁻² at −0.85 V (vs. RHE) and a high faradaic efficiency (FE) of 34.2% at −0.45 V (vs. RHE). The ¹⁵N isotopic labelling experiments confirm that the yielded NH₃ is, indeed, from the CuCo₂O₄ spinel catalyzed NtRR process. Our theoretical calculations results reveal that the NO₃⁻ can be adsorbed on the CuCo₂O₄ to form the *NOH intermediate, leading to a good selectivity and FE.