Modulating Zr single-atom electronic structure via axial S-induced distortion for enhanced oxygen reduction

Asymmetric Zr single-atom sites with axial S atom are constructed. • Efficient oxygen reduction reaches 0.913 V with 110 h stability. • Electronic structure is tuned to optimize intermediate adsorption. • Breaking the scaling relationship enables improved ORR kinetics. Asymmetry engineering in single-atom catalysts (SACs) has emerged as a powerful approach to modulate electrocatalytic performance. However, Zr-based SACs have been rarely investigated for the oxygen reduction reaction (ORR) due to limited synthetic precedents and unclear coordination-activity relationships. Here, we report a novel A -S-Zr-N 2 O 2 @NC catalyst in which axial sulfur incorporation creates an asymmetric Zr-N/O/S coordination environment, inducing electronic redistribution and generating highly active catalytic sites. The catalyst exhibits a half-wave potential (E 1/2 ) of 0.913 V, surpassing commercial Pt/C and most state-of-the-art non-noble-metal nanomaterials, while maintaining excellent Zn-air battery (ZAB) durability over 28 days and high methanol tolerance. Mechanistic studies confirm that S atom enhances *OOH adsorption on Zr sites, breaks the scaling relationship, and lowers the O-O bond cleavage barrier, enabling an efficient four-electron reaction pathway. Our findings highlight the immense potential of the Zr-based SACs platform for electrocatalysis, elucidate the mechanistic role of asymmetric ligand engineering, and provide a rational design framework for high-performance catalytic materials. Download: Download high-res image (166KB) Download: Download full-size image