Climbing the Apex of the ORR Volcano Plot via Binuclear Site Construction: Electronic and Geometric Engineering

Abstract

Great enthusiasm in single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) has been aroused by the discovery of M-N_X as a promising ORR catalysis center. However, the performance of SACs lags far behind that of state-of-the-art Pt due to the unsatisfactory adsorption-desorption behaviors of the reported catalytic centers. To address this issue, rational manipulation of the active site configuration toward a well-managed energy level and geometric structure is urgently desired, yet still remains a challenge. Herein, we report a novel strategy to accomplish this task through the construction of an Fe-Co dual-atom centered site. A spontaneously absorbed electron-withdrawing OH ligand was proposed to act proactively as an energy level modifier to empower easy intermediate desorption, while the triangular Fe-Co-OH coordination facilitates O-O bond scission. Benefiting from these attributes, the as-constructed FeCoN₅-OH site enables an ORR onset potential and half-wave potential of up to 1.02 and 0.86 V (vs RHE), respectively, with an intrinsic activity over 20 times higher than the single-atom FeN₄ site. Our finding not only opens up a novel strategy to tailor the electronic structure of an atomic site toward boosted activity but also provides new insights into the fundamental understanding of diatomic sites for ORR electrocatalysis.