Improving the Catalytic Efficiency of Electrochemical Nitrogen Reduction Reaction (NRR) through Surface Modification and Nanostructured Bimetallic Catalysts

Abstract

Electrochemical nitrogen reduction is recognized as a promising and sustainable alternative to the conventional Haber-Bosch method to produce ammonia. However, there are many challenges that pose significant barriers to the practical application of the nitrogen reduction reaction (NRR). These challenges are primarily attributed to the strong triple bond in the N2 molecule and the competing hydrogen evolution reaction (HER). This work investigates the synergy between alloys and nanostructured bimetallic systems and the application of molecular overlayers to improve efficiency and production rate of ammonia on the catalyst surface. We studied the combination of a noble metal catalyst scaffold modified with active metals (Li/Mg) that is known to cleave the N-N bond. Solvent effects were also tested in both aqueous and non-aqueous media to see changes in catalyst effects. Additionally, various experimental controls were performed including argon controls, isotope labeling, and assessing NOX contaminants to ensure that the reaction was interacting with our catalyst. Overall, this work demonstrates the use of molecular overlayers on nanostructured bimetallic systems to control hydrophobicity of catalyst surface and improve faradaic efficiency, ammonia production rate, catalyst durability and current density. Relationships between these parameters helped understand NRR mechanism and will help guide future NRR catalyst design.