LAUSR

In this work, for the first time an in situ electrochemical pretreatment approach to fabricate a highly reversible oxygen electrode with redistributed ultrafine RuO2 catalysts on a carbon nanotube (CNT) matrix is reported. The optimally pretreated RuO2/CNT oxygen electrodes demonstrate an extremely stable cycling life, 800 times with non‐Li metal anode, under a capacity‐limited protocol of 800 mAh g−1 in an ether‐based electrolyte in an O2 environment. The highly stable activity of ultrafine RuO2 catalysts in oxygen reduction and evolution processes originates from the synergetic effect of greatly reduced size of catalyst (<2 nm) and uniform redistribution of catalyst particles after the in situ electrochemical pretreatment process. The pretreatment method discovered in this work can not only significantly enhance the activity/efficiency of the catalysts used for air electrodes but can also be widely applied to other electro‐catalysis systems.