Theoretical insights into graphenylene-based triple-atom catalysts for efficient nitrogen fixation

Ammonia synthesis from the electrochemical nitrogen reduction reaction, which can weaken but not directly break the inert NN bond via multiple progressive protonation steps under mild conditions, has been recognized as one of the most attractive alternatives for the production of NH₃. In this work, the potential of employing graphenylene-based triple-atom catalysts for the nitrogen reduction reaction was investigated by using first-principles calculations. The performance of these catalysts was studied focusing on configuration optimization, thermal stability, catalyst selectivity and activity and the interaction mechanism. There was electron transfer between the transition metal atoms and the graphenylene substrate, which strengthens the structure stability of the complex systems and brings about sufficient catalytic activity. A more negative ΔG (N₂) for the nitrogen reduction reaction than ΔG (H) for the hydrogen evolution reaction is selected as an evaluation standard of good selectivity. Moreover, ΔG (*N*NH) or ΔG (*NNH) < 0.6 eV is used as a screening criterion for good activity. By screening, Mo₃@GP is found to show the best nitrogen reduction reaction performance with a low limiting potential of -0.39 V through a consecutive pathway. The excellent performance derives from the largest electron transfer ability of Mo₃ atoms and the electronic reservoir function of the GP substrate.