Closing the nitrogen loop: sustainable ammonia production from industrial nitrate waste using a stacked electrolyzer

Abstract

Nitrate in wastewater poses a significant threat to the aquatic ecosystem and disrupts the nitrogen cycle. In this study, we developed a stacked electrolyzer capable of converting nitrate in industrial effluents, even at low concentrations, into green ammonia (NH₃) through the nitrate reduction reaction. Our catalyst synergistically transforms the nitrates into vital intermediates (NO_x), which are then further reduced to NH₃. The stacked electrolyzer achieved a faradaic efficiency of 37% and an NH₃ yield of ∼7.8 mg h⁻¹ when treating low-concentration industrial wastewater (1000 ppm). Additionally, it demonstrated a wastewater processing capacity of 5 L day⁻¹ with a single-pass ammonia recovery of 27.7%. Overall, our approach of producing green ammonia from nitrate-laden effluents represents a promising solution for closing the nitrogen cycle.