Balanced NO<sub><i>x</i></sub><sup>–</sup> and Proton Adsorption for Efficient Electrocatalytic NO<sub><i>x</i></sub><sup>–</sup> to NH<sub>3</sub> Conversion
Yue Hu, Jiawei Liu, Carmen Lee, Wenyu Luo, Jinfeng Dong, Zhishan Liang, Mengxin Chen, Erhai Hu, Mingsheng Zhang, Xiang Yun Debbie Soo, Qiang Zhu, Fengkun Li, Rajdeep Singh Rawat, Man‐Fai Ng, Lixiang Zhong, Bo Han, Dongsheng Geng, Qingyu Yan
Abstract
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.