Valorization systems based on electrocatalytic nitrate/nitrite conversion for energy supply and valuable product synthesis

Abstract

The excessive accumulation of nitrate/nitrite (NO_x⁻) in surface and groundwater has severely disrupted the global nitrogen cycle and jeopardized public health. The electrochemical conversion of NO_x⁻ to ammonia (NH₃) not only holds promise for ecofriendly NO_x⁻ removal, but also provides a green alternative to the energy-intensive Haber–Bosch process for NH₃ production. Recently, in addition to the electrocatalyst design explosion in this field, many innovative valorization systems based on NO_x⁻-to-NH₃ conversion have been developed for generating energy and expanding the range of value-added products. Collective knowledge of advanced conversion systems is indispensable for restoring the global nitrogen cycle and promoting a N-based economy. Herein, a timely and comprehensive review is provided on the important progress of valorization systems based on NO_x⁻ conversion, including waste treatment systems, novel electrolytic systems, and energy conversion and storage systems. Some mechanism explorations, device designs, key electrode developments and feasibility analyses are involved to gain deeper understanding of various systems and facilitate implementing these cleaning systems in industry. Finally, challenges and future prospects are outlined in the NO_x⁻ conversion field with an aim to promote large-scale electrocatalytic system development and prosperous N-based electrochemistry.