Iron Single-Atom Catalysts Anchored on Defect-Engineered N‐Doped Graphene Reveal an Interplay between CO2 Reduction Activity and Stability

The precise engineering of vacancies in nitrogen-doped graphene(NG) presents a promising strategy for stabilizing metal single-atom catalysts(SACs) and tuning their catalytic performance. We explore the role of vacanciesin NG for stabilizing iron-based SACs (Fe-SACs) by using density functionaltheory (DFT). First, we examine the stability of various vacancy types in grapheneand NG supports, addressing the question of preferential formation of specificstructural defects as potential sites for metal binding. We reveal simple rulesgoverning the stability of vacancies and show that nitrogen doping can bringabout vacancy healing. We identify preferred binding sites for Fe atoms/ions,specifically single and double vacancies, and analyze how the nitrogen-dopingpattern in a vacancy affects the interaction of Fe with the SAC support. Theresults show that the positions of nitrogen(s) and the local charge environmentsignificantly influence the stability of the Fe-SACs. Notably, some Fe@NGconfigurations, although not the most thermodynamically stable, exhibit enhanced catalytic performance, particularly for a CO2 reduction reaction (CO2RR). These findings offer valuable insights into vacancy engineering as a strategy for designing high- performance Fe-SACs and emphasize the interplay among vacancy types, nitrogen concentration, and catalyst stability in driving the catalytic behavior.