Atomically engineering TiN surfaces with single-atom catalysts for targeted nitrate electroreduction

Continuous nitrate accumulation in water bodies has disrupted the global nitrogen cycle equilibrium, posing significant challenges for sustainable development. Electrocatalytic nitrate reduction to high-value ammonia (NH     3) presents a promising cost-effective approach for pollution remediation and green ammonia production. However, designing efficient electrocatalysts with high stability, activity, and selectivity for the nitrate reduction reaction (NO     3RR) remains a formidable challenge. In this study, we computationally explored the performance of a series of 3     d-5     d transition metal single-atom catalysts (SACs) supported on a defective TiN(100) surface for the NO     3RR. Through a comprehensive four-step screening process involving catalyst stability, nitrate adsorption, activity screening, and selectivity evaluation, two promising catalysts, Nb@TiN and Ta@TiN, were identified. These catalysts facilitate stable nitrate adsorption and substantially suppress the formation of undesirable by-products (NO and NO     2), thereby enabling highly selective ammonia production. The superior NO     3RR activity originates from their      d-band centers being in close proximity to the Fermi level, facilitating strong orbital hybridization and sufficient charge transfer with the adsorbed nitrate species. This work reports the first instance of highly efficient NO     3RR electrocatalysts based on transition metal SACs supported on TiN, providing a promising new avenue for ammonia recovery from wastewater and offering significant theoretical guidance for sustainable green ammonia synthesis.