Critical Role of Explicit Inclusion of Solvent and Electrode Potential in the Electrochemical Description of Nitrogen Reduction

The electrocatalytic nitrogen reduction reaction (NRR) is one of the most promising ways to achieve NH3 production at room temperature and pressure. However, there exists significant disagreement between the theoretically predicted potentials required for the NRR by the conventional quantum-theoretical calculations and those observed experimentally. Here, an explicit computational model incorporating the solvation effect and electrode potential has been proposed for NRR on single iron atoms supported on nitrogen-doped graphene. We find that the aqueous environment plays an essential role in NRR by promoting N2 adsorption, whereas the electrode potential impacts considerably on the electrode-electrolyte interface where NRR occurs. The constrained molecular dynamics (cMD) simulations and a thermodynamic integration method are used to explore the free energy profiles of N2 adsorption and the proton transfer process. The results are consistent with experimental observations, i.e., the NRR can take place at a relatively low electrode potential, thus revealing the critical role of the explicit inclusion of the solvation effect and electrode potential in computationally studying electrochemical reactions. With this approach, we have provided atomic-level mechanistic insights into the electrode-electrolyte interface for NRR through electrochemical catalysis.