Discovering a catholyte free design for gas phase electrocatalytic NO gas reduction to NH3 at room temperature

• Published in: Journal of environmental chemical engineering 2023-10, Vol.11 (5), p.110751, Article 110751
• Main Authors: Ramu, A.G., Renukadevi, R., Silambarasan, P., Moon, Il-Shik, Govindarasu, Mydhili, Choi, Dongjin
• Format: Article
• Language: English
• Subjects: Electrode-electrolyte free; Gas phase reduction; NH3 yield rate; NO removal; Value added products
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2023.110751

Nitric oxide (NOx) is one of the most contributors to the health risks associated with breathing in flue gases and it is crucial to eliminate this pollutant from the air when solid waste is burned. Electrochemical gas phase reduction of NO to NH3 is the promising method to mitigating the accumulation of NO gas pollutants and producing a valuable NH3 as a product at room temperature. In this investigation, for the first time, we designed a catholyte-free cell for gas phase electrochemical NO to NH3 conversion using K2[Ni(CN)4] coated carbon felt (CF) electrode as a electrocatalyst at room temperature. Herein, K2[Ni(CN)4] heterogeneous mediator transfers the electron between the NO gas molecule and electrode. The NO removal efficiency and NH3 formation were simultaneously monitored by using online gas phase FTIR spectroscopy. In the catholyte-free gas phase NORR process, the K2[Ni(CN)4]/CF electrode exhibits excellent NORR performance, with a high NH3 yield rate of 1128.9 µmol h−1 cm−2, an excellent 89.5 % NH3 faradaic efficiency at − 1 V vs quasi reference Ag and enhanced long term NORR durability. It is noteworthy that, this is the highest yield rate and faradaic efficiency of NH3 during gas phase NORR at room temperature. In addition, K2[Ni(CN)4]/CF electrocatalyst exhibits 99 % of NO removal efficiency with the formation of value-added product (NH3). Moreover, the proposed electrocatalyst shows excellent chemical, and morphological stability after long durability NORR operations. Furthermore, the detailed electrode-electrolyte free cell, NORR reduction mechanism was proposed. Present discovery provides great insights for sustainable NORR operations in real-site applications. [Display omitted] •Successful design of a catholyte-free gas phase electrochemical cell for NO to NH3 conversion.•Highest NH3 yield rate and faradaic efficiency achieved at room temperature.•Impressive 99 % NO removal efficiency with the formation of value-added product (NH3).•Excellent long-term stability of the K2[Ni(CN)4]/CF electrocatalyst during NORR operations.