Cost and Performance Targets for Fully Electrochemical Ammonia Production under Flexible Operation

Abstract

Methods to produce ammonia from air, water, and renewable electricity are necessary to transition ammonia production away from the CO₂-emitting Haber–Bosch process. In this vein, a fully electric process in which water-splitting-derived hydrogen and air-separation-derived nitrogen are reacted in an electrochemical process to produce ammonia is attractive. Herein, we evaluated the cost-effectiveness of large-scale fully electric ammonia production relying on renewable electricity sources in conjunction with different types of storage and flexible operation using a mixed-integer linear programming framework. We found that ammonia can be produced in an economically competitive manner, i.e., at costs < 1 $/kg, at large scales if the electrochemical reactor can produce ammonia at partial currents exceeding 400 mA cm⁻², energy efficiencies exceeding 30%, and process lifetimes of several years. In light of this, alternative chemistries that can reduce nitrogen at high rates and moderate (<2.5 V) overpotentials are necessary for economical, fully electrochemical ammonia production.