Triple-phase oxygen electrocatalysis of hollow spherical structures for rechargeable Zn-Air batteries

The high-efficient and low-cost oxygen electrocatalysts are of significant importance but challenge in energy storage and conversion devices. The oxygen electrocatalysis involves triple-phase interfaces of solid catalyst, liquid electrolyte and gaseous oxygen. The reaction microenvironment in which the ample transmission pathway sufficiently feeds the highly active sites and expulses product rapidly is typically desired. Herein, the reaction interface microenvironment of hollow spherical bimetallic electrocatalyst (CoFe-SNC) is regulated via structural architecture engineering, achieving the ample triple-phase contact points of O2 (gas), electrolyte (liquid) and electrocatalyst (solid). Sufficient O2 supply and unimpeded mass transfer afforded by triple-phase interface flourish catalytic efficiency and enhance oxygen electrocatalysis. Simultaneously the incorporation of sulfur dopant improves the intrinsic catalytic activity, giving rise to highly active sites in reaction interface of CoFe-SNC. With such well-constructed triple-phase interface microenvironment, the CoFe-SNC shows outstanding oxygen reduction reaction activity (E1/2 = 0.86 V vs RHE) and stability in basic media, and a low charging–discharging voltage gap (1.19 V) with excellent durability is realized in rechargeable Zn–air batteries.