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 x Sb y 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 x Sb y 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 x Sb y 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 pi* interaction. Subsequently, the occupied Bi 6p orbital electrons are transferred to the pi* antibonding orbital of N2, which greatly weakens the N equivalent to N bond strength, thereby reducing the nitrogen reduction reaction (NRR) rate-limiting barrier (*N equivalent to N -> *N equivalent to 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 (R NH3 ) and faradaic efficiency (FE) of 2D-Bi x Sb y series catalysts are higher than those of Bi Ns and Sb Ns. After optimization, the 2D-Bi0.5Sb0.5 catalyst exhibits the best NRR performance (R NH3 : 5.13 x 10-10 mol s-1 cm-2, FE: 28.15%) and has superior electrochemical stability. After stability tests, the R 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.