Bi-Sn bimetallic catalysts for efficient electrocatalytic nitrogen reduction to ammonia

Abstract

The development of efficient electrocatalysts for sustainable ammonia synthesis via the nitrogen reduction reaction remains a critical challenge due to the inherent stability of N ≡ N bonds and competing hydrogen evolution reaction. Herein, we present a bimetallic Bi-Sn catalyst synthesized through galvanic replacement and electrodeposition, demonstrating enhanced nitrogen reduction performance under ambient conditions. The optimized Bi-Sn catalyst achieves an ammonia yield of 17.09 μg h⁻¹·mg_cat⁻¹ with a Faradaic efficiency of 5.37 % at −0.4 V vs. reversible hydrogen electrode, representing an obvious improvement over pristine Bi. Comprehensive characterization reveals that Sn nanoparticles are uniformly decorated on the Bi surfaces, increasing the electrochemical surface area while enhancing electrode conductivity. Theoretical calculations elucidate the synergistic mechanism: Sn modulates the Bi 6p band center, reducing the energy barrier for the rate-determining step of ∗N₂ → ∗NNH by 16.9 % (ΔG = 1.72 eV vs. 2.07 eV for Bi) and enhancing nitrogen adsorption (0.20 eV vs. 0.28 eV). This work establishes an integrated strategy of structural engineering and electronic modulation for designing bimetallic catalysts, advancing sustainable ammonia synthesis.