Aligned d-orbital energy level of dual-atom sites catalysts for oxygen reduction reaction in anion exchange membrane fuel cells

Abstract

The inherent scaling relationships between adsorption energies of oxygen-containing intermediates impose an intrinsic limitation on the maximum oxygen reduction reaction (ORR) activity, which represents one of the bottlenecks for the practical application of anion exchange membrane fuel cells (AEMFCs). To address this challenge, we align the 3dz² orbital energy levels of Fe and Co to selectively customize the dissociative ORR pathway without the formation of OOH* intermediates, circumventing the conventional OH*-OOH* scaling relations. This rational design is achieved by atomic phosphorus(P) substitution, which not only optimizes orbital matching towards O-O cis-bridge adsorption, but also stabilizes the spontaneously adsorbed OH ligand as an electronic modifier. Due to these attributes, the well-designed FeCo-N/P-C catalyst demonstrates ORR performance with a current density of 251 mA·cm^-2 at 0.9 V_iR-free under 1.5 bar H₂-O₂, showing a competitive performance with state-of-the-art Pt-free electrocatalysts and meeting the 2025 DOE target (44 mA·cm^-2). More importantly, the peak power density reaches as high as 0.805 W·cm^-2 under 1.5 bar H₂-air with negligible degradation observed over 10,000 cycles of voltage accelerated stress testing. This work offers a highly competitive electrocatalyst for AEMFCs and opens an effective avenue to bypass the constraints of linear scaling relations for ORR and beyond.