Balanced NO and Proton Adsorption for Efficient Electrocatalytic NO to NH Conversion.

Electrocatalytic nitrate (NO)/nitrite (NO) reduction reaction (eNORR) to ammonia under ambient conditions presents a green and promising alternative to the Haber-Bosch process. Practically available NO sources, such as wastewater or plasma-enabled nitrogen oxidation reaction (p-NOR), typically have low NO concentrations. Hence, electrocatalyst engineering is important for practical eNORR to obtain both high NH Faradaic efficiency (FE) and high yield rate. Herein, we designed balanced NO and proton adsorption by properly introducing Cu sites into the Fe/FeO electrocatalyst. During the eNORR process, the H adsorption is balanced, and the good NO affinity is maintained. As a consequence, the designed Cu-Fe/FeO catalyst exhibits promising performance, with an average NH FE of ∼98% and an average NH yield rate of 15.66 mg h cm under the low NO 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 (23.5 mM) in KOH electrolyte, the Cu-Fe/FeO catalyst achieves an FE of ∼99% and a yield rate of 15.1 mg h cm for NH production at -0.5 V (vs RHE). The performance achieved in this study exceeds industrialization targets for NH production by exploiting two available low-concentration NO sources.