Aqueous electrolyte effect on the electrochemical green ammonia production Sara Garcia Ballesteros 1 , Noemi Pirrone 1 , Simelys Hernández 1 and Federico Bella 1,2 1 Politecnico di Torino, Italy, 2 INSTM, Italy Ammonia (NH 3 ) has been extensively produced and utilized as a fertilizer for more than a century, at present is emerging as a promising alternative renewable energy carrier and storage intermediate for global use. 1–3 Thus far, NH 3 is produced via the high energy-demanding Haber-Bosh process (HBP), which consumes 1-2% of fossil fuels worldwide, contributing to the greenhouse effect by releasing the equivalent of ca. 2% of total CO 2 global emissions. 4–6 So, the development of alternative, green and sustainable processes that challenge this century-old process is crucial. Electrochemical nitrogen (N 2 ) reduction reaction (E-NRR) is a suitable technology widely recognised as an alternative option to the traditional HBP. The main challenge of E-NRR in aqueous electrolytes is the optimization of the system to suppress the competing hydrogen evolution reaction (HER). At present, most of the works employ a H-type cell; however, the flow cell reactor with a gas-diffusion electrode (FC-GDE) shows clear advantages as it reduces mass transfer limitations due to low N 2 solubility and allows efficient and quick NH 3 recovering. Although most of the literature works focus on electrocatalyst design, the electrolyte is vital since it essentially determines the electrode reactions, being responsible for selectivity and efficiency. The aim of the present work is to gain further insight into the effect of aqueous electrolyte characteristics on E-NRR process efficiency. The activity and stability of a commercial molybdenum disulphide catalyst (MoS 2 ) combined with different formulated electrolytes (LiSO 4 , LiClO 4 , K 2 SO 4 and NaBF 4 at different concentrations and pH) have been tested. A FC-GDE on which the catalyst is immobilized through air-brushing technique has been used to perform all the experiments. Promising results have been obtained when employing Li + as a cation in the electrolyte since it can promote MoS 2 NRR activity thanks to the modification of the crystalline structure after Li + ions intercalation. 7 The studied catalyst/electrolyte combination made it possible to obtain Faradaic efficiencies between 5 and 10%, and 85-301 μmol g -1 h -1 yield at -0.6 V vs. RHE. With these promising results, further experiments are being carried out to find the optimum electrolyte concentration, pH, potential and gas and liquid flow rate. References 1. Valera-Medina, A., et al. Energy Combust. Sci. 69, 63–102 (2018). Shen, H., et al. Chem 7, 1708–1754 (2021). 2. Choi, J., et al. Nat. Commun. 11, (2020). 3. Chen, S., et al. Materials Today Nano vol. 18 100202 Niu, L., et al. J. Energy Chem. 61, 304–318 (2021). 4. Xu, H., et al. Nano Energy 69, 104469 (2020).Patil, S. B., et al. Mater. Chem. A 9, 1230–1239 (2021).
P20
© The Author(s), 2023
Made with FlippingBook Learn more on our blog