Enhancing Ammonia Production Rate from Electrochemical Nitrogen Reduction by Modifying Cu Catalyst and Three-Phase Boundary

Ammonia (NH₃) is a critical component in fertilizer and other essential industrial chemical production, making it the second largest synthetic chemical worldwide (&gt; 200 million tons). However, the traditional Haber-Bosch process requires massive energy input and results in the emission of a large amount of carbon dioxide [1,2].<br/>The electrochemical nitrogen reduction reaction (eNRR) driven by renewable electricity under mild condition emerges as a sustainable method for NH₃ production to minimize carbon footprint [3,4]. We are focusing on the development of an effective eNRR system using Cu-based electrocatalysts in gas diffusion electrode (GDE) system with modification of three-phase interfaces. To overcome the low affinity of Cu for N₂, phosphorus activation was applied to create electron-deficient Cu sites for better N₂ adsorption and activation. Additionally, we address the limited solubility of nitrogen in aqueous electrolytes by incorporating a GDE coated with polytetrafluoroethylene (PTFE). This setup optimizes the three-phase interfaces among water, gaseous N₂, and the catalyst. Our innovative approach in a flow-type cell achieves a Faradaic efficiency of 13.15% and an ammonia production rate of 7.69 μg h^-1 cm^-2 at -0.2 V_RHE. This represents a 59.2-fold increase in NH3 production rate compared to electrodeposited Cu electrodes, highlighting the potential of our strategies in practical systems [3].<br/>[1] Y. Zeng, C. Priest, G. Wang, G. Wu, Restoring the Nitrogen Cycle by Electrochemical Reduction of Nitrate: Progress and Prospects, Small Methods, 4 (2020) 2000672.<br/>[2] B. Yang, W. Ding, H. Zhang, S. Zhang, Recent Progress in Electrochemical Synthesis of Ammonia from Nitrogen: Strategies to Improve the Catalytic Activity and Selectivity, Energy Environ. Sci., 14 (2021) 672-687.<br/>[3] J. Kim, C.H. Lee, Y.H. Moon, M.H. Lee, E.H. Kim, S.H. Choi, Y.J. Jang, J.S. Lee, Enhancing Ammonia Production Rates from Electrochemical Nitrogen Reduction by Engineering Three-Phase Boundary with Phosphorus-Activated Cu Catalysts, J. Energy Chem., 84 (2023) 394-401.