Molybdenum Atom-Mediated Salphen-Based Covalent Organic Framework as a Promising Electrocatalyst for the Nitrogen Reduction Reaction: A First-Principles Study

The electrocatalytic nitrogen reduction reaction (NRR) has garnered significant attention from the scientific community because it is considered a simple, green, and sustainable method for ammonia (NH3) production. However, the lack of suitable electrocatalysts with high activity and selectivity prevents the large-scale production of NH3 through electrocatalytic N2 fixation. To search potential electrocatalysts for NRR, herein, using density functional theory (DFT)-based calculations, we investigated the suitability of a molybdenum atom-doped salphen-based covalent organic framework (Mo-salphenCOF) as an electrocatalyst toward NRR. Our findings suggest that Mo-salphenCOF is both thermodynamically and electrochemically stable. Mo-salphenCOF displays excellent electrocatalytic activity toward NRR with a very low limiting potential of −0.33 V vs a reverse hydrogen electrode (RHE) through the preferred distal mechanism. Mo-salphenCOF displays a low kinetic barrier of 0.42 eV at 0 V vs RHE for the least thermodynamically favored step along the most favored distal pathway. As far as the catalytic selectivity of Mo-salphenCOF is concerned, it can moderately suppress the competing hydrogen evolution reaction (HER) both at zero and NRR operating potential (−0.33 V vs RHE) with a substantial theoretical faradic efficiency (FE) of 41%. Moreover, the inclusion of an implicit solvation model showed positive results for both the activity and selectivity of our proposed electrocatalyst (Mo-salphenCOF) toward NRR. Therefore, the high stability, excellent catalytic activity, and substantial catalytic selectivity of Mo-salphenCOF make it a potential candidate as an electrocatalyst toward NRR.