Electrochemical formation of ammonia from nitrates in wastewater using a liquid metal electrode Anthony O'Mullane and Jessica Crawford Queensland University of Technology, Australia Ammonia production via the traditional Haber Bosch reaction is highly energy intensive and results in an overall process that has significant CO 2 emissions. Therefore, alternative green approaches for the production of ammonia are highly sought after. One such approach is the electrochemical conversion of nitrates in aqueous solution to ammonia. This is emerging as a highly promising route for the synthesis of ammonia both for the fertiliser industry but also as a potential fuel and hydrogen carrier [1]. However, the creation of highly efficient electrocatalysts with prolonged stability is an ongoing challenge. In this talk I demonstrate that room temperature liquid metal Galinstan, a eutectic of Ga, In and Sn, can be used as an electrocatalyst for nitrate conversion to ammonia.The use of liquid metals has opened up some new and interesting features such as very high atom utilisation efficiency[2]and stability to poisoning [3,4]. This makes liquid metal electrodes interesting candidates for application in electrocatalytic reactions. In this workrates of up to 2335 µg h -1 cm -2 with a Faradaic efficiency of nearly 100% could be achieved. The electrocatalyst was also stable for multiple cycles of conversion of nitrates to ammonia. Density functional theory (DFT) calculations and experimental observation indicated that the active site for the reaction is In 3 Sn which becomes enriched within the liquid metal during the electrocatalytic reaction. The high selectivity for NH 3 is also ensured due to the suppression of the hydrogen evolution reaction which is often a highly problematic competing reaction for this process.
References 1. Shiozawa, B. (2023). Potential of Ammonia as CO 2 -Free Fuel and Hydrogen Carrier. In: Aika, Ki., Kobayashi, H. (eds) CO 2 Free Ammonia as an Energy Carrier. Springer, Singapore. https://doi.org/10.1007/978-981-19-4767-4_3. 2. A. Rahim, J. Tang, A. J. Christofferson, P. V. Kumar, N. Meftahi, F. Centurion, Z. Cao, J. Tang, M. Baharfar, M. Mayyas, F.-M. Allioux, P. Koshy, T. Daeneke, C. F. McConville, R. B. Kaner, S. P. Russo, K. Kalantar-Zadeh, Nature Chemistry 2022, 14, 935. 3. O. Oloye, C. Tang, A. Du, G. Will, A. P. O'Mullane, Nanoscale 2019, 11, 9705. 4. Esrafilzadeh, A. Zavabeti, R. Jalili, P. Atkin, J. Choi, B. J. Carey, R. Brkljača, A. P. O’Mullane, M. D. Dickey, D. L. Officer, D. R. MacFarlane, T. Daeneke and K. Kalantar-Zadeh, Nature Communications, 2019, 10, 865.
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