Transition-Metal-Doped Hexagonal Boron Nitride for Efficient and Selective Nitrate-to-Ammonia Electrocatalysis:...

Escalating nitrate contamination in water resources underscores the urgent demand for remediation strategies that not only eliminate nitrates but also enable valorization. The electrochemical nitrate reduction reaction (NO₃RR) offers such a dual solution by converting NO₃ ^- into ammonia (NH₃), a cornerstone chemical in fertilizers and energy applications. Here, we employ first-principles calculations to systematically evaluate a family of transition-metal-doped hexagonal boron nitride (TM@h-BN, TM = Ti-Au) monolayers. Our results identify Fe@h-BN and Ir@h-BN as highly promising single-atom catalysts, exhibiting low limiting potentials of -0.45 V and -0.31 V, respectively, for efficient NH₃ production. The exceptional performance of these catalysts arises from their balanced interaction with NO₃ ^-, which provides sufficient adsorption without over-stabilization, while their intrinsically weak hydrogen binding suppresses the competing hydrogen evolution reaction (HER). Moreover, the elevated potentials for byproduct pathways (NO₂, NO, N₂O, N₂) impart excellent selectivity toward NH₃ formation. To generalize these mechanistic insights, we integrate a SISSO-based machine learning framework that uncovers key descriptors governing NO₃RR catalyst performance and establishes a general equation linking limiting potential and fundamental catalyst properties. Collectively, this work not only expands the design landscape of h-BN-anchored single-atom catalysts but also provides a transferable design principle for next-generation electrocatalysts, paving the way toward sustainable NH₃ production and water resources.