C₃N-supported IIIA group metal single-atom catalysts with different coordination microenvironments: Electrocatalytic NO reduction to ammonia

Electrochemical NO reduction reaction (NORR) to NH3 is regarded as a low-cost and environmentally friendly method that can simultaneously remove harmful NO and synthesize useful NH3. Using main group metal (MGM) atoms as active centers has the potential to enhance the selectivity of single-atom catalysts (SACs) for NH3. Herein, we selected Al, Ga and In atoms as active centers and designed 12 MGM SACs supported on the defective C3N monolayer with four coordination environments: MGM-C2N, MGM-C3, MGM-C2N2 and MGM-C4. Based on density functional theory (DFT) calculations, the NORR electrocatalytic performance of these 12 SACs were systematically investigated. Detailed studies on the NORR mechanism show that seven of these SACs exhibit excellent activity in reducing NO to NH3, effectively preventing the formation of byproducts (N2O, N2 and H2). Further stability calculations led to the identification of five promising NORR electrocatalysts with both excellent catalytic performance and stability: Al/Ga/In-C2N2 and Ga/In-C4. Moreover, the Bader charge (QMGM) of the MGM atom was used to explain the variation in activity resulting from different coordination environments. This work not only provides valuable insights for future exploration of MGM SACs, but also contributes to a better understanding of the impact of coordination environments on catalytic activity.