DFT Study on the Electrocatalytic NO Reduction Performance of Sc Single-Atom Catalysts for Automotive Exhaust NOx Control

Electrocatalytic nitric oxide reduction (NORR) shows great potential for mitigating NOx emissions from motor vehicles and other internal combustion engine exhausts, enabling the resource utilization of pollutant NO and the synthesis of NH3 under mild conditions. The overall performance of NORR largely depends on the development of efficient electrocatalysts. Based on a coordination-engineering strategy, this study constructs a series of Sc-based single-atom catalyst systems coordinated with nonmetal heteroatoms (X = B, C, O, Si, P, S, As, Se, Te), denoted as Sc@XN3, and systematically investigates their NORR reaction pathways, limiting potentials (UL, the minimum applied potential required to make all elementary steps downhill in free energy), and selectivity using density functional theory (DFT) calculations. The results indicate that Sc@CN3, Sc@PN3, and Sc@SN3 possess relatively low UL, with values of −0.17, −0.31, and −0.07 V, respectively, among which Sc@SN3 is thermodynamically the most favorable. Moreover, Sc@CN3 and Sc@SN3 can suppress the hydrogen evolution reaction (HER) and the formation of N2O/N2 by-products, thereby affording higher selectivity toward NH3 formation. Considering the characteristics of NOx emissions from engine exhaust, these coordination-engineered Sc centers show promising potential for future electrified aftertreatment systems that couple NOx control with ammonia-based energy utilization in vehicles. This study clarifies at the atomic scale how the coordination environment modulates the electronic structure and catalytic behavior of Sc single-atom centers and provides theoretical guidance for the rational design of high-performance NORR electrocatalysts targeted at automotive exhaust NOx control.