Efficient Electrocatalytic Nitrogen Reduction to Ammonia on Ultrafine Sn Nanoparticles

Electrocatalytic nitrogen reduction reaction (NRR) at ambient conditions is a promising route for ammonia (NH₃) synthesis but still suffers from low activity and selectivity. Here, ultrafine Sn nanoparticles (NPs) grown on carbon blacks (Sn_SC/C) have been synthesized through a wet-chemical method using sodium citrate dehydrate as a stabilizing agent. Benefiting from the small sizes of Sn NPs, the Sn_SC/C catalyst exhibits excellent electrocatalytic performance for NRR with a high Faradaic efficiency of 22.76% and an NH₃ yield rate of 17.28 μg h^-1 mg^-1 in the 0.1 M Na₂SO₄ electrolyte, outperforming many reported electrocatalysts for NRR under similar conditions. Density functional theory calculation results reveal that the potential-determining step on Sn NPs is the generation of NHNH* through simultaneous hydrogenation of N₂^* by a H* and a H⁺/e^- pair via Langmuir-Hinshelwood plus Eley-Rideal mechanisms.