2020/02/14 by Joshua M. McEnaney, Sarah J. Blair, Adam C. Nielander +4 · 8 citations
Chemical Engineering · Energy · Computer Science · #Ammonia Synthesis and Nitrogen Reduction #Advanced Photocatalysis Techniques #Caching and Content Delivery
paper · doi:10.1021/acssuschemeng.9b05983
openalex publication_date 2020/02/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Nitrates from agricultural runoff and industrial waste streams are a notorious waste product and hazardous pollutant. Traditional electrochemical water remediation approaches aim to solve this problem by converting nitrates to environmentally benign N 2 while minimizing the production of environmentally hazardous side products such as ammonia and nitrous oxide in a process known as “denitrification”. We modify this concept and outline an opportunity to optimize the conversion of nitrates into ammonia, which is also a key commodity product used as a fertilizer, potential fuel, and chemical precursor. The electrochemical conversion of nitrates to ammonia recycles the fixed nitrogen and offers an appealing and supplementary alternative to the energy- and resource-intensive Haber-Bosch process. In this study, we investigated the effect of varying electrochemical conditions (pH, nitrate concentration, and applied potential) on the selective reduction of nitrate to ammonia at a titanium cathode. We observed that high concentrations of both protons and nitrate ions are needed to achieve high selectivity, reaching a peak of 82% Faradaic efficiency to ammonia at an applied potential of −1 V versus RHE and a partial current density to NH 3 of −22 mA/cm 2, using 0.4 M [NO 3 – ] at pH ∼0.77. The Ti electrode, as a poor hydrogen evolution catalyst with notable corrosion resistance, provides a large window of operating conditions to achieve high selectivity in the reduction of nitrate anions. Stability of the system was evaluated, and we found a high Faradaic efficiency throughout the course of an 8 h experiment. After electrochemical testing, titanium hydride was observed at the cathode surface. We also show a preliminary technoeconomic study, indicating that it may be feasible to employ an electrochemical strategy for the production of ammonium nitrate.