Breaking Dilution Limits: Electrocatalytic Ammonia Production from Low-Concentration Nitrate Streams.

Abstract

The conversion of nitrate (NO₃ ^-) in water to high-value-added ammonia (NH₃) using an electrocatalytic NO₃ ^- reduction reaction (eNO₃ ^-RR) provides a viable technological pathway to address the imbalance in the global nitrogen cycle. Unfortunately, most of the existing studies have focused on the ideal conditions of high-concentration NO₃ ^-, but most of the polluted waters around the world are usually at low-concentration levels. Consequently, researching eNO₃ ^-RR under low-concentration NO₃ ^- is more practical. Although the study of low-concentration NO₃ ^- has gradually gained attention in recent years, a systematic review of the literature in this area has not yet been reported. To fill this research gap, this paper reviews recent advances in the electrocatalytic reduction of low-concentration NO₃ ^- to NH₃. Initially, the nature of NO₃ ^- as a reactant, the reaction mechanism of eNO₃ ^-RR, and the factors affecting the efficiency are introduced. Subsequently, the key challenges of electrocatalytic reduction of low-concentration NO₃ ^- are analyzed, and various strategies to improve the performance of eNO₃ ^-RR are summarized on this basis. Additionally, the feasibility of large-scale ammonia recovery using eNO₃ ^-RR under low-concentration NO₃ ^- is assessed through application scenario exploration, economic analyses, and life cycle assessment. Ultimately, future research directions are outlined to inspire future work.