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| Home > Publications database > Understanding Nitrate Electrochemical Reduction to Ammonia by Identifying Changes in pH |
| Poster (After Call) | FZJ-2025-00027 |
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2024
Abstract: Electrochemical nitrate reduction into ammonia is an attractive technology that promotes nitrates removal from wastewater while delivering ammonia as a profitable product. The high concentration of nitrates in the wastewater of the agricultural and various industrial sectors is a serious pollution problem with serious consequences for the environment and public health.[1] On the other hand, ammonia is one of the most demanded chemical substances worldwide since it is a raw material for different products, mainly fertilizers, plastics, and fuels [2]. Therefore, understanding the electrochemical conversion of nitrates to ammonia in aqueous media and under ambient conditions is a key element both to address water pollution and to ensure ammonia supply. Electrochemical nitrates reduction to ammonia in aqueous media under ambient conditions has been reported, using noble metal-based electrodes (e.g., Ru, Rh, Pt). [2] It has been shown that nitrates reduction is a complex process due to its polyatomic nature, forming several intermediate compounds before its complete reduction into ammonia. The ammonia selectivity depends on the electrocatalyst, the applied potential, and the electrolyte media. [3] Jaramillo’s group studied the effect of the initial pH electrolyte on the ammonia Faradaic efficiency, concluding ammonia formation is favored at low pH (<1).[1] Clearly, pH plays an essential role in nitrates reduction. However, there is limited knowledge of pH changes through the reaction, since only initial pH is reported, and how and why such changes impact the ammonia selectivity. In this work, the changes in pH during the electrochemical reduction of nitrates to ammonia are evaluated using Ti and Cu-foils. We investigate four different electrolytes ranging from pH 1 to pH 10, tracking the changes in pH over the course of a 30 min experiment. Our results show that when the initial pH is equal to or above pH 3 the media undergoes alkalinization, reaching pH values close to 12. On the other hand, in acidic conditions the pH only increases slightly. In addition, the highest faradaic efficiency is obtained at more alkaline initial conditions. The intermediate products are also detected and correlated to the pH increase.
Keyword(s): Chemical Reactions and Advanced Materials (1st) ; Basic research (1st) ; Chemistry (2nd) ; Others (2nd) ; Materials Science (2nd)
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