Nitrogen reduction reaction (NRR) boosting by ionic liquids on iron-modified molybdenum sulfide electrodes Pablo Barraza 2 , Mauricio Isaacs 1 , Rodrigo del Río 1 , Domingo Ruiz 2 1 Pontifica Universidad Católica de Chile, Chile, 2 Universidad de Santiago de Chile, Chile Ammonia (NH 3 ) is one of the most demanded chemical substances worldwide, mainly due to its use as a raw material for the synthesis of fertilizers. It is estimated that the industrial production of NH 3 by Haber-Bosh process consumes 1% of the fossil fuel used in a year worldwide, and produces 2 tons of CO 2 for each ton of ammonia, which corresponds to 1.5% of total CO 2 emissions in a year 1 . The nitrogen reduction reaction (NRR) has shown to be a possible way to obtain ammonia, but to date, this reaction has not been able to be carried out with a high faradaic yield, mainly due to the fact that the electrodes where it is carried out reduction reaction, presenting greater affinity towards hydrogen adsorption. Therefore, hydrogen evolution (HER) tends to inhibit NRR 2 . On the one hand, based on Nørskov's studies that have shown that molybdenum and iron are two of the metallic elements that present a greater adsorption towards the N2 molecule 3 , three compounds based on molybdenum sulfide are presented. modified with iron (MoS2), synthesized by a hydrothermal methodology: MoS2-Fe, MoS2- FeS2 and MoS2-Fe dots. Each synthesized compound has been characterized by XPS, Raman and XRD. On the other hand, based on the concept of “supported ionic liquid phase” (SILP) 4 , we have used a series of hydrophobic ionic liquids from the bis(trifluoromethylsulfonyl)imide ([NTf2]) family, with the purpose of achieving a surface with restricted access to water molecules. To carry out the electrochemical characterizations, the compounds were dispersed in a liquid phase, then a specific amount of ionic liquid was added to the mixture and finally were deposited on a glassy carbon electrode. Cyclic and linear voltammetry were performed in saturated environments of Ar and N 2 using sodium sulfate (Na 2 SO 4 ) as a supporting electrolyte. Finally, the electrocatalytic efficiency of the compounds in the reduction of N 2 to generate ammonia was evaluated. For this, electrolysis was carried out at different potentials for 3 hours. The Ammonia were detected and quantified by UV-VIS electron spectroscopy.
Figure 1 shows the electrocatalytic activity of MoS 2 -Fe for NRR in the presence of ionic liquids of the [NTf2] family. It is observed that the amount of current generated increases as a function of the size of the carbon chain of the cationic group. References 1. A. Martin, T. Shinogawa, J.perez-Ramirez, Chem, 5 (2019) 263-283. 2. Y. Ren, C. Yu, X. Tan, H. Huang, Q. Wei, J. Qui, Energy environmental science, 14 (2021). 3. E. Skulason, T. Bligaard, S. Gudmundsdottir, F. Studt, J. Rossmeisl, F. Abild-Pedersen, T. Vegge, H. Jonsson, J. Nørskov, A theoretical evaluation of possible transition metal electro-catalysts for N2 reduction, Physical Chemistry Chemical Physics, 14 (2012) 1235-1245. 4. G. Zhang, B. Etzold, Emerging Applications of Solid Catalysts with Ionic Liquid Layer Concept in Electrocatalysis, Adv. Funct. Mater, 31 (2021).
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