Dual-regulated cascade catalysis via spatial synergy and electronic coupling for efficient oxygen reduction reaction

Abstract

Fe-NC materials have emerged as promising alternatives to platinum-based catalysts for oxygen reduction reaction (ORR). Yet, their performance remains constrained by the intrinsic linear scaling relationship of single-active-site configuration, leading to sluggish kinetics. Herein, a feasible dual-site cascade electrocatalyst was synthesized via a simple one-step pyrolysis, featuring in-situ formed uniformly dispersed ZnS nanoparticles synergistically integrated with FeN₄-enriched N, S-codoped carbon matrices (denoted as ZnS-Fe-NSC). Comprehensive experimental and theoretical investigations reveal a sophisticated cascade mechanism: The activation of oxygen preferentially occur at the ZnS sites, facilitating rapid generation and migration of the *OOH intermediate, while adjacent FeN₄ centers with optimized electronic structures effectively reduce energy barriers for subsequent electron transfer steps. This spatial-electronic dual regulation successfully reconstructs the conventional single-site reaction pathway, achieving remarkable performance enhancements. The optimized catalyst demonstrates an exceptional half-wave potential of 0.96 V (120 mV improvement over single-site counterparts) with near-theoretical four-electron selectivity. And the kinetic current density at 0.8 V reaches 44.52 mA cm⁻², 5.6 times that of commercial Pt/C. When applied in zinc-air batteries, the ZnS-Fe-NSC-based air cathode achieves a peak power density of 193 mW cm⁻² and sustains stable operation for over 200 h. this work not only overcomes the performance limitations of Fe-NC catalysts but also establishes a universal framework for designing multi-component ORR catalysts through spatial synergy and electronic coupling effects, providing critical insights for developing high-efficiency non-precious metal electrocatalysts