N-heterocyclic carbene coordinated single atom catalysts on C₂N for enhanced nitrogen reduction

Abstract

Single-atom catalysts (SACs) with N-heterocyclic carbene (NHC) coordination provide an effective strategy for enhancing nitrogen reduction reaction (NRR) performance by modulating the electronic properties of the metal active sites. In this work, we designed a novel NHC-coordinated SAC by embedding transition metals (TM) into a two-dimensional C₂N-based nanomaterial (TM@C₂N-NCM) and evaluated the NRR catalytic performance using a combination of density functional theory and machine learning. A multi-step screening identified eight high-performance catalysts (TM = Nb, Fe, Mn, W, V, Ta, Zr, Ti), with Nb@C₂N-NCM showing the best performance (limiting potential = -0.29 V). All catalysts demonstrated lower limiting potential values compared to their TM@graphene-NCM counterparts, revealing the effectiveness of the C₂N substrate in enhancing catalytic activity. Machine learning analysis achieved high predictive accuracy (coefficient of determination = 0.91; mean absolute error = 0.19) and identified final step protonation (S₆), Mendeleev number (N_m), and d-electron count (N_d) as key factors influencing catalytic performance. This study offers valuable insights into the rational design of NHC-coordinated SACs and highlights the potential of C₂N-based nanomaterials for advancing high-performance NRR electrocatalysts.

Keywords

Nitrogen reduction reaction / single-atom catalysts / N-heterocyclic carbenes / C₂N / machine learning

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