Atomistic Simulations Facilitating the Synthesis of the Desired Fe–Cu–N–C Dual-Atomic Site for Acidic Oxygen Reduction in Fuel Cells

Abstract Advancing Fe–N–C single-atom catalysts is paramount for sustainable proton-exchange membrane fuel cells. Dual-atom catalysts offer the most transformative strategy, as they are inherently more active than single-atom catalysts. However, controlling their local coordination environment during synthesis to a desired structure remains a formidable challenge, restricting current high-impact studies to heuristic methods for designing efficient dual-atom catalysts. Studying the promising Fe–Cu–N–C catalyst, we theoretically identify that the most active and stable site for the oxygen reduction reaction features an Fe–Cu bond in N4-coordination environments, N4 Fe–Cu–N–C. By combining X-ray absorption spectroscopy (XAS) with density functional theory, we determine that the synthesis step creating metal-vacant N–C ligands is essential for yielding the desired N4 Fe–Cu–N–C sites. In H2–O2 fuel cells, N4 Fe–Cu–N–C exhibits superior stability with 34.5% voltage loss in 156 h, whereas Fe–N–C loses 50.0% in 90 h. Mechanistic insights reveal that the formation of an Fe–Cu bond induces a charge redistribution effect, strengthening the neighboring bonds in the dual-atom moiety to boost catalyst durability. Aligning with theoretical findings, operando cyclic voltammetry and XAS elucidate that the N4 Fe–Cu–N–C fuel cells effectively suppress detrimental Fe2+/Fe3+ redox processes, thereby preventing carbon corrosion and demetalation, the two major degradation pathways. This rational protocol for catalyst design can enable greater control over the synthesis of intricate local coordination environments in dual-atom sites, thereby contributing to the development of stable, low-cost hydrogen fuel cells.