Electronic structure and catalytic activity of TM@Mg12O12 nanocages for ambient ammonia synthesis

• Novel transition metal atoms doped Mg 12 O 12 nanocages as single atom catalysts have been designed. • These catalysts are thermodynamically stable with interaction energies of −2.49 to −0.48 eV. • Transition-metal atom decoration of Mg 12 O 12 nanocages greatly enhances N 2 activation efficiency. • Mn@Mg 12 O 12 shows a low limiting potential (−0.84 V) for ambient ammonia synthesis. • These findings provide new routes for designing efficient catalysts for sustainable nitrogen reduction. The development of low-cost and efficient electrocatalysts for the ambient nitrogen reduction reaction (NRR) is essential for the synthesis of NH 3 and offers a substitute for the conventional Haber-Bosch process. In the present work, density functional theory (DFT) is employed to investigate the electrochemical nitrogen reduction reaction (NRR) catalysed by TM@Mg 12 O 12 (TM=Sc ∼ Zn) nanocages. All complexes exhibit chemisorption interactions with interaction energies ranging from −2.49 eV to −1.11 eV, except Zn@ Mg 12 O 12 (−0.48 eV) which shows physisorption. The energy gaps (E g ) of TM@Mg 12 O 12 are significantly reduced compared with pristine Mg 12 O 12 indicating enhanced conductivity. Electronic properties and interaction types were analyzed using density of states, natural bond orbital, interaction region indicator, and quantum theory of atoms in molecules analyses. The results reveal that TM doping notably enhances N 2 activation relative to pure Mg 12 O 12 . Among all candidates, Mn@Mg 12 O 12 exhibits the highest NRR activity, with a limiting potential of −0.84 V along the alternating pathway. The stability and energetics of intermediates were further assessed to determine the optimal reaction mechanism for NH 3 synthesis. This study provides fundamental insights into the rational design of single-atom catalysts supported on three-dimensional nanocages, contributing to the development of efficient electrocatalysts for ambient ammonia synthesis.