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Electrocatalytic nitrate (NO 3 – )/nitrite (NO 2 – ) reduction reaction (eNO x – RR) to ammonia under ambient conditions presents a green and promising alternative to the Haber–Bosch process. Practically available NO x – sources, such as wastewater or plasma-enabled nitrogen oxidation reaction (p-NOR), typically have low NO x – concentrations. Hence, electrocatalyst engineering is important for practical eNO x – RR to obtain both high NH 3 Faradaic efficiency (FE) and high yield rate. Herein, we designed balanced NO x – and proton adsorption by properly introducing Cu sites into the Fe/Fe 2 O 3 electrocatalyst. During the eNO x – RR process, the H adsorption is balanced, and the good NO x – affinity is maintained. As a consequence, the designed Cu–Fe/Fe 2 O 3 catalyst exhibits promising performance, with an average NH 3 FE of ∼98% and an average NH 3 yield rate of 15.66 mg h –1 cm –2 under the low NO 3 – concentration (32.3 mM) of typical industrial wastewater at an applied potential of −0.6 V versus reversible hydrogen electrode (RHE). With low-power direct current p-NOR generated NO x – (23.5 mM) in KOH electrolyte, the Cu–Fe/Fe 2 O 3 catalyst achieves an FE of ∼99% and a yield rate of 15.1 mg h –1 cm –2 for NH 3 production at −0.5 V (vs RHE). The performance achieved in this study exceeds industrialization targets for NH 3 production by exploiting two available low-concentration NO x – sources.
Hu et al. (Sat,) studied this question.