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

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.