Axial electron-conduction engineering of single-atom copper catalyst for kinetic-fast oxygen reduction

Abstract

Single-atom catalysts with metal-N₄ sites demonstrate good activity in the oxygen reduction reaction (ORR), yet the symmetric electronic structure limits its ability to differentially regulate oxygen-containing intermediates, resulting in sluggish kinetics. To address this, we have developed an axial chlorine-mediated strategy to break the symmetry of the copper-N₄ structure, thereby achieving superior ORR activity. Ax-Cl-Cu/NC catalyst was synthesized by coordinating an axial chlorine atom to the Cu-N₄ sites on an NC support. The as-prepared Ax-Cl-Cu/NC catalyst exhibits outstanding ORR performance, achieving nearly 99% four-electron selectivity and a large mass activity of 4,430.6 A g_metal^-1 at 0.85 V - 67.4 times higher than Pt/C (65.73 A g_metal^-1). The superior performance of the Ax-Cl-Cu/NC catalyst is further demonstrated in a lab-assembled Zinc-air battery, which achieves stable operation for over 100 h. A series of experimental characterizations confirmed that the introduction of an axial chlorine atom reduced the electron density of the Cu center, alleviating the over-stabilization of oxygen intermediates and facilitated the cleavage of the O-O bond. This work establishes a new paradigm for designing high-efficiency non-precious metal ORR catalysts.

Keywords

Axial coordination / single-atom / in situ synchronous radiation infrared spectroscopy / oxygen reduction reaction

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