Computational screening of single-atom alloys TM@Ru(0001) for enhanced electrochemical nitrogen reduction reaction

Abstract

Searching for highly efficient, active, and stable electrocatalysts for the nitrogen reduction reaction is vital to supersede the energy-intensive Haber–Bosch process. The electrocatalytic nitrogen reduction reaction (NRR) is one of the most promising strategies to synthesize value-added ammonia (NH₃) under mild conditions with low energy utilization and less greenhouse gas emission. However, the lack of effective electrocatalysts remains the major hurdle for its practical applications. Ruthenium is generally considered a promising electrocatalyst for the electrochemical NRR. However, it exhibits a high overpotential corresponding to the potential determining step in the reduction pathway. Herein, using density functional theory, we systematically investigated the potential of a series of transition metal-doped Ru-based TM@Ru(0001) (TM = Sc–Zn, Y–Cd) single-atom alloys to evaluate their NRR activity. Among all the studied catalysts, it was found that the V doped Ru(0001) SAA exhibited a reduced kinetic barrier of about 1.14 eV as compared to that of the pure Ru(0001) corresponding to the potential determining step (PDS). In addition, it showed a significantly low negative limiting potential of −0.15 V for the PDS along with thermodynamical stability and high selectivity over the competing hydrogen evolution reaction (HER). The Climbing-Image Nudged Elastic Band (CI-NEB) method was employed to calculate the barrier height between various hydrogenation steps of the reduction reaction followed by the calculation of turnover frequency (TOF) for V@Ru(0001) using a microkinetic modelling approach. The TOF for V@Ru(0001) was found to be 4.24 × 10⁻³ per s per site at 100 bar and 700 K, which is far better than that of the pure Ru(0001) surface. This report provides a new design strategy to improve the catalytic performance of Ru(0001) for effective NRR.