Main-Group Metal Atoms Anchored on Borophene/Al(111) as an Efficient Catalyst for Electrocatalytic Nitrate Pollutant Reduction Reactions: A First-Principle Perspective

Ammonia is essential for sustainable development, and electrochemical nitrate reduction (e-NitRR) enables simultaneous nitrate remediation and ammonia recovery. Here, main-group single atoms anchored on honeycomb borophene/Al(111) (M-HB/Al(111)) were systematically investigated. Screening based on binding energies, aggregation tendencies, and molecular dynamics identified nine stable configurations among eleven candidates. Li-HB/Al(111) and Na-HB/Al(111) exhibited outstanding activity, with limiting potentials of −0.04 and −0.13 V, respectively. Charge density and projected density-of-states analyses revealed an ‘‘ionic-bond fixation and electron bridge’’ mechanism, in which metal sites stabilize NO3- through ionic interactions and facilitate electron transfer from the substrate to intermediates. Moreover, a descriptor integrating NO3− adsorption free energy, atomic radius, and valence electron number correlated strongly with catalytic activity. These findings identify efficient main-group electrocatalysts, clarify the atomic-scale reaction mechanism, and establish quantitative principles for rational e-NitRR catalyst design, providing theoretical guidance for nitrate valorization and sustainable ammonia production in practical aqueous treatment systems.