Boosting Faradaic Efficiency in Electrochemical Nitrogen Reduction with a Trimetallic CuSnAu@NF Electrocatalyst for Sustainable Ammonia Synthesis

The electrochemical nitrogen reduction reaction (ENRR) provides a green, sustainable alternative to the energy-intensive Haber-Bosch process for synthesizing ammonia and reduces its environmental impact significantly. In this research, we developed a CuSnAu electrocatalyst immobilized onto nickel foam (CuSnAu@NF) using solvothermal methods and galvanic replacement reactions to improve its performance. First, CuSn was synthesized by the solvothermal method. Adding Au atoms (0.2%) to the CuSn structure by galvanic replacement increases the number of active sites for nitrogen adsorption and at the same time prevents the hydrogen evolution reaction. The replacement of Au atoms increased the faradaic efficiency from 7.14 to 60.88%, and the NH₃ yield improved from 10.94 μg h⁻¹ cm⁻² (1.78 × 10⁻¹⁰ mol s⁻¹ cm⁻²) at -0.4 V vs RHE to 19.66 μg h⁻¹ cm⁻² (3.2 × 10⁻¹⁰ mol s⁻¹ cm⁻²) at -0.15 V vs RHE. The incorporation of Au decreased the adsorption energies of reaction intermediates, hence accelerating reaction kinetics as determined by DFT simulations. The faradaic efficiency and NH₃ yield of the electrocatalyst were satisfactory and consistent throughout multiple runs, exhibiting no degradation of the electrocatalyst. The CuSnAu@NF electrocatalyst demonstrates potential as an efficient and stable electrocatalyst for sustainable ammonia production at ambient conditions.