Two-Dimensional BiSb Alloy Nanosheets for the Electrochemical Conversion of Nitrogen-to-Ammonia in Neutral Electrolytes

To achieve efficient and sustainable NH₃ production by electrochemical nitrogen reduction at room temperature, the catalyst must have high activity and superior stability. Here, we prepared a series of two-dimensional Bi_<i>x</i>Sb_<i>y</i> alloy nanosheet materials with different atomic ratios by the improved coreduction method. Experiments and density functional theory (DFT) calculations reveal the following. (i) The uniformly distributed two-dimensional Bi_<i>x</i>Sb_<i>y</i> alloy nanosheet catalysts not only have a larger specific surface area, thereby promoting the full exposure of Bi active sites, but also are conducive to enhance the electrochemical stability of catalysts. (ii) In 2D-Bi_<i>x</i>Sb_<i>y</i> alloys, the effective charge coupling between Bi-Sb sites bridges the electron transfer channel from Bi to Sb, thereby improving the charge structure of Bi active sites, which enhances the adsorption of N₂ by Bi sites and the Bi 6p-N₂ π* interaction. Subsequently, the occupied Bi 6p orbital electrons are transferred to the π* antibonding orbital of N₂, which greatly weakens the N≡N bond strength, thereby reducing the nitrogen reduction reaction (NRR) rate-limiting barrier (*N≡N → *N≡N-H: 0.26 eV). (iii) BiSb alloying further increases the hydrogen adsorption free energy (0.28 eV), preventing more hydrogen from occupying active sites, thereby inhibiting hydrogen evolution reaction (HER). Therefore, the NH₃ yield (<i>R</i>_NH₃) and faradaic efficiency (FE) of 2D-Bi_<i>x</i>Sb_<i>y</i> series catalysts are higher than those of Bi Ns and Sb Ns. After optimization, the 2D-Bi_0.5Sb_0.5 catalyst exhibits the best NRR performance (<i>R</i>_NH₃: 5.13 × 10^-10 mol s^-1 cm^-2, FE: 28.15%) and has superior electrochemical stability. After stability tests, the <i>R</i>_NH₃ and FE retention rates are as high as 98.28 and 98.07%, respectively. This study provides valuable insights into the design of novel ternary alloy NRR catalysts.