Mechanistic Insights into Electrocatalytic Nitrogen Reduction Reaction on the Pd‐W Heteronuclear Diatom Supported on C2N Monolayer: Role of H Pre‐Adsorption

The electrocatalytic N2 reduction reaction (eNRR) is a potential alternative to the Haber–Bosch process for ammonia (NH3) production. Tremendous efforts have been made in eNRR catalyst research to promote the practical application of eNRR. In this work, by means of density functional theory calculations and the computational hydrogen electrode model, we evaluated the eNRR performance of 30 single metal atoms supported on a C2N monolayer (M@C2N), and we designed a new thermodynamically stable Pd‐W hetero‐metal diatomic catalyst supported on the C2N monolayer (PdW@C2N). We found that PdW@C2N prefers to adsorb H over N2, and then, the pre‐generated hydrogen‐terminated PdW@C2N selectively adsorbing N2 behaves as the actual functioning “catalyst” to catalyze the eNRR process, exhibiting excellent performance with a low overpotential (0.31 V), an ultra‐low NH3 desorption free energy (0.05 eV), and a high selectivity toward eNRR over hydrogen evolution reaction (HER). Moreover, PdW@C2N shows a superior eNRR performance to its monomer (W@C2N) and homonuclear diatom (W2@C2N) counterparts. The revealed mechanism indicates that the preferential H adsorption over N2 on the active site may not always hamper the eNRR process, especially for heteronuclear diatom catalysts. This work encourages deeper exploration on the competition of eNRR and HER on catalyst surfaces. A thermodynamically stable Pd‐W hetero‐metal diatomic catalyst supported on the C2N monolayer (PdW@C2N) was designed for high‐efficient electrocatalytic nitrogen reduction reaction. The key role of pre‐generated hydrogen‐terminated PdW@C2N in catalytic mechanism was revealed.