Tuning the Selectivity for High Yield Ammonia Production in Electrochemical Nitrate Reduction using Sulfur and Nitrogen‐Rich Carbon Catalyst

Abstract The electrocatalytic nitrate (NO ₃ ⁻ ) reduction reaction (NO ₃ RR) offers a promising pathway for synthesizing value‐added ammonia (NH ₃ ) while removing NO ₃ ⁻ pollutants. However, this reaction is hindered by NO ₃ ⁻ adsorption and slow kinetics involving multiple proton and electron transfer steps. In pursuit of an efficient catalyst, a sulfur and nitrogen‐rich carbon catalyst, SNC 700, with a cuboidal morphology is presented for selective electrochemical NO ₃ ⁻ reduction to NH ₃ . The SNC 700 catalyst exhibited a higher NH ₃ Faradaic efficiency (F.E.) of 97.83% and an extremely low F.E. of nitrite (NO ₂ ⁻ , ≈ 0.69%) compared to the counterpart NC 700 catalyst (F.E. _NH3 42.85%, F.E. _NO2‐ 9.92%) at a potential of −0.6 V vs. RHE. Complementary insights from in‐situ Raman spectroscopy and microelectrochemical studies revealed the reaction pathway, highlighting a rapid reduction of NO ₃ ⁻ intermediate and more favorable hydrogenation over SNC 700 catalyst compared to NC 700. This suggests that incorporating sulfur into the nitrogen‐containing carbon structure enhances hydrogen adsorption, leading to improved NO ₃ ⁻ to NH ₃ selectivity. This work presents a straightforward and practical approach to address the challenges of limited NO ₃ ⁻ reduction selectivity, particularly for carbon‐based materials.