DFT–kMC Analysis for Identifying Novel Bimetallic Electrocatalysts for Enhanced NRR Performance by Suppressing HER at Ambient Conditions Via Active-Site Separation

Abstract

As an alternative to the traditional Haber-Bosch process for ammonia synthesis under high temperature and pressure, the electrochemical nitrogen reduction reaction (NRR) under ambient conditions has been getting attention. Although ruthenium (Ru) is considered the holy-grail catalyst for the NH3 process, it suffers from low selectivity due to the competition between NRR and hydrogen evolution reaction. Experimental screening of new candidate catalysts that can circumvent this challenge is highly resource-intensive, requiring significant labor and expensive precursors. To address this challenge, we have combined density functional theory and kinetic Monte Carlo to shortlist high-performing NRR catalysts. Specifically, this framework utilizes a combination of thermodynamic, electronic, and kinetic analyses to investigate different bimetallic catalysts (i.e., RuTi, RuV2, Ru3W, RuZn3, and RuZr) with specially designed separate active sites for N2 and H adsorption to enhance NRR performance. Our investigations revealed that the newly suggested RuV2 has superior NRR activity with decreased thermodynamic overpotential and increased reaction rates that surpass those of Ru. Notably, RuV2 shows a high N2 selectivity by significantly reducing H poisoning on the catalyst surface and increasing the amount of NH3 with a turnover frequency of 1.1 × 10–4 s–1 under mild conditions (300 K and 1 bar), which is 1 000 times greater than that of a pure Ru electrocatalyst. Given these key observations, we believe our framework can play a pivotal role in elucidating the role of different active sites for NRR and can be extended to other high-impact metallic catalyst families in the future.