Diatomic nitrogen-fixation electrocatalysts supported on graphitic carbon nitride achieve significantly low over potentials

The construction and screening of diatomic catalysts (DAC), as well as the exploration of intrinsic descriptors, are attracting increasing attention. In this work, using graphitic carbon nitride (g-CN) as the substrate, we assembled W, Mo, Cr, Mn, Fe, Co, and Ni atoms into DAC and conducted a systematic exploration of the catalytic capabilities of these systems for nitrogen reduction reaction (NRR) using first-principles calculations. Our research demonstrates that MoMn@g-CN exhibits outstanding catalytic activity and selectivity among the investigated 28 catalysts. The overpotential for NRR on MoMn@g-CN along the enzymatic pathway is merely 0.10 V, which is lower than most of the reported catalysts. By conducting in-depth electronic structure calculations, the catalytic mechanism of the DAC is investigated. N₂ adsorption and activation are influenced by the σ-acceptor-π∗-donor mechanism. The enhanced activation of nitrogen molecules is attributed to the synergistic effect of two hetero-diatomic species. Moreover, we have identified an new intrinsic descriptor for NRR related to the electronegativity of the two transition metal atoms. This descriptor correlates with the volcano plot of NRR's limiting potential. Our findings can provide valuable insights for the design and high-throughput screening of DAC.