4d Metal-doped liquid Ga for efficient ammonia electrosynthesis at wide N2 concentrations

Abstract

Electrocatalytic nitrogen reduction reaction under ambient conditions is a promising pathway for ammonia synthesis. Currently nitrogen reduction reactions are carried out in N₂-saturated environments and use high-purity nitrogen as feedstock, which is costly. Here, we prepared carbon-coated ultra-low 4d metal Ru-doped liquid metal Ga (Ru_0.06/LM@C) for NRR over a wide range of N₂ concentrations. Comprehensive analyses show that the introduction of the ultra-low 4d element Ru can effectively adjust the electronic structure through orbital interactions, thus enhancing the adsorption of nitrogen-containing intermediates. The liquid catalyst utilized its mobility to provide a higher density of active sites. In addition, the material Ru_0.06/Ga@C itself has the ability to promote product desorption. The three act synergistically to optimize the N₂ mass transfer path, thereby increasing the *NNH coverage and further improving the ammonia yield over a wide range of N₂ concentrations. The maximum NH₃ yield of the catalyst can reach 126.0 μg h⁻¹ mg_cat⁻¹ (at –0.3 V vs. RHE) with high purity N₂ as feed gas, and the Faraday efficiency is 60.4% at –0.1 V vs. RHE. Over a wide range of N₂ concentrations, the NH₃ yield of the catalyst was greater than 100 μg h⁻¹ mg_cat⁻¹ with a Faraday efficiency higher than 47%. The catalytic performance is much higher than that of solid Ga@C and reported p-block metal-based catalysts.