Strategies and applications of electrocatalytic nitrate reduction towards ammonia

The electrocatalytic nitrate reduction reaction (NO3RR) provides an appealing and sustainable pathway to achieve valuable ammonia (NH3) production and realize wastewater denitrification, but there remain challenging problems including sluggish reaction kinetics, low NH3 yield, and poor selectivity. Unlike most of the reviews in literature which summarize the progress of electrocatalysts in this field with a focus on the types of catalysts and electronic structures, this review starts from the practical perspective and places the emphasis on the key solutions and the potential applications. Besides the reaction mechanisms and the performance evaluation criteria, the current scientific problems in NO3RR are summarized. Both the latest achievements and the proposed important strategies are elaborately discussed. More importantly, aiming at realizing the scale-up of NO3RR to NH3, the applicability in ammonium fertilizer production, Zn-NO3− batteries, value-added chemical production, and CO2 absorption is analyzed. Furthermore, in situ characterization techniques and theoretical calculations for mechanism understanding and catalyst design are also summarized, and future directions and prospects of NO3RR are provided as well. This review is proposed to provide in-depth insights into the industrialization of NH3 electrosynthesis for energy conservation and environmental sustainability.