(Invited) Activating Nitrogen for Electrochemical Ammonia Synthesis: Modeling the Effects of Electrified Interfaces on π-Backbonding Molecules

Abstract

Electrocatalysts are expected to play a pivotal role in shaping our future sustainable energy landscape by enabling storage of renewable energy and its conversion into globally important chemicals. Computational simulations yield mechanistic insights that have supported catalyst discovery and optimization. However, the complexity of electrocatalyst interfaces has necessitated the development of quantum chemical methods that can accurately model these effects at reasonable computational cost.In this work, we employ grand canonical density functional theory (GC-DFT) to capture the nuanced effects of applied potential on a solvated catalyst interface, specifically focusing on the nitrogen reduction reaction (NRR) at sulfur vacancies in 1T'-phase MoS2. In the canonical method, the widely used the computational hydrogen electrode (CHE) predicts that adsorbed N2 structure properties are potential independent. In contrast, GC-DFT calculations reveal that reductive potentials activate N2 towards electroreduction by modulating backbonding strength, lengthening the N–N triple bond, and reducing its bond order. Similar trends are identified for CO, a classic backbonding ligand, suggesting broader relevance of this mechanism to diverse electrochemistries involving backbonded adsorbates. Furthermore, reductive potentials are required to make the subsequent N2 hydrogenation steps favorable, but concurrently destabilize both N2 and hydrogen adsorption.Our findings demonstrate that GC-DFT facilitates the comprehensive modeling of these phenomena, underscoring their collective implications in predicting electrocatalyst selectivity for the nitrogen reduction reaction and potentially other reactions. This research contributes valuable insights into the design and optimization of electrocatalysts for sustainable energy conversion. Figure 1