Diatomic Active Sites\nEmbedded Graphyne as Electrocatalysts\nfor Ammonia Synthesis

Ammonia (NH<sub>3</sub>) is a vital chemical compound\nin industry\nand agriculture, and the electrochemical nitrogen reduction reaction\n(eNRR) is considered a promising approach for NH<sub>3</sub> synthesis.\nHowever, the development of eNRR faces the challenge of high overpotential\nand low Faradaic efficiency. In this work, graphyne (GY) is anchored\nby 3d, 4d, and 5d dual transition metal atoms to form diatomic catalysts\n(DACs) and is roundly investigated as an electrocatalyst for eNRR\nvia density functional theory calculations. Due to the protrusion\nof anchored metal atoms, the active sites of GY are better exposed\ncompared to other substrates, exhibiting higher activity. Through\nfour-step hierarchical high-throughput screening (Δ<i>G</i><sub>*N<sub>2</sub></sub> < 0 eV, Δ<i>G</i><sub>*N<sub>2</sub> → *N<sub>2</sub>H</sub> < 0.4\neV, Δ<i>G</i><sub>*NH<sub>2</sub> → *NH<sub>3</sub></sub> < 0.4 eV, and Δ<i>G</i><sub>*N<sub>2</sub></sub> < Δ<i>G</i><sub>*H</sub>), the number\nof selected catalysts in each step is 325, 240, 145, and 20, respectively.\nConsidering a series of factors, including stability, initial potential,\nand selectivity, 13 kinds of eligible catalysts are identified. Optimal\neNRR paths studies show that the best catalyst Mn<sub>2</sub>@GY features\nno onset potential. For the three catalysts (Mn<sub>2</sub>@GY, Ir<sub>2</sub>@GY, and RhOs@GY), the onset potentials of the most favorable\neNRR pathways are −0.07, −0.12, and −0.17 V,\nrespectively. The excellent catalytic activity can be credited to\nthe effective charge transfer and orbital interaction between the\nactive site and adsorbed N<sub>2</sub>. Our work demonstrates the\nsignificance of DACs for ammonia synthesis and provides a paradigm\nfor the study of DACs even for other important reactions.