Restricting Two-Electron Oxygen Reduction via Secondary Coordinated Sulfur Enabling Ultralong-Lifespan Zn-Air Batteries

Abstract

The direct four-electron oxygen reduction reaction (4e− ORR) critically governs efficiency and lifespan in metal–air batteries and fuel cells, yet selectively suppressing competitive 2e− and stepwise 2e−pathways that generate corrosive hydrogen peroxide remains a major challenge. Herein, we demonstrate the strategic incorporation of secondary coordinated sulfur atoms into transition metal-N-C electrocatalysts to effectively promote direct 4e− ORR and simultaneously suppress undesirable 2e− pathways. Density functional theory (DFT) calculations and operando spectroscopy reveal that enhanced adsorption of key intermediate *OOH facilitates efficient O─O bond cleavage, underpinning altered catalytic selectivity. Importantly, this approach is universally applicable to various carbon-based catalysts, including Co─N@C, Ni─N@C, Mn─N@C, and N@C. Specifically, a sulfur-mediated Co─N/Co@C catalyst, comprising Co─N4 sites and Co nanoparticles, dramatically lowers the 2e− O2-to-H2O2 rate constant to merely 0.05-fold of its original value at 0.78 V. Consequently, Zn-air batteries using Co─N/Co@C-S as cathode exhibits an outstanding peak power density of 220 mW cm−2, remarkable lifespan over 2500 h, and outstanding rate performance from 5 to 50 mA cm−2. This work paves a generalizable route for designing highly active and selective electrocatalysts suitable for advanced long-life energy storage devices.