Unraveling the Electronic Origin of High Activity and Selectivity of Single-Atom Catalyst for NO Electroreduction

Abstract

The electrochemical reduction of nitric oxide (NO) to ammonia (NH₃) is an emerging technology with dual benefits for environmental remediation and resource conversion. However, this process still faces significant challenges, including low catalytic activity, poor selectivity, and severe competition from side reactions. In this study, we systematically investigated the catalytic behavior of transition metal singleatom catalysts (TM@g-C₄N₃) anchored on a novel two-dimensional carbon nitride material (g-C₄N₃) for the NO reduction reaction (NORR) using first-principles density functional theory (DFT) calculations. Six candidate catalysts were identified as stable under both thermodynamic and electrochemical conditions. Their electronic structures, NO adsorption and activation abilities, and reaction pathways were thoroughly analyzed. The results reveal that the Ag single-atom catalyst exhibits the best catalytic performance, with the lowest limiting potential and excellent selectivity toward NH₃.Further analysis shows that the d-band center of the Ag atom is farthest from the Fermi level, leading to an optimal adsorption strength for NO and thereby the highest catalytic activity. This study not only proposes an effective screening strategy for highperformance NORR catalysts but also provides theoretical guidance for the rational design of novel electrocatalytic materials.