Ultrafine IrO2 nanoparticle-decorated carbon as an electrocatalyst for rechargeable Li-O2 batteries with enhanced charge performance and cyclability

Ultrafine iridium (IV) oxide (IrO2) nanoparticles are homogeneously distributed on the surface of porous Ketjenblack (KB) carbon (IrO2/KB) via one-step hydrothermal approach, and the resulting nanocomposite is investigated as an electrocatalyst for nonaqueous Li-O-2 batteries. Transmission electron microscopy confirms the high dispersion of ultrafine IrO2 particles with an average particle size of 1.47 nm. The IrO2/KB electrode exhibits remarkable catalytic activity towards oxygen evolution reaction (OER) as indicated by the voltammetric measurements. And, the IrO2/KB electrode decreases the recharge overpotential by ca. 400 and 200 mV compared to the electrodes with pure KB and a mechanical mixture of KB and pre-synthesized IrO2, respectively. Li-O-2 battery with IrO2/KB achieves high-capacity retention and stable cyclability, maintaining a long cycle life for 70 cycles without sharp decay under a limited discharge-charge depth of 500 mAh g(-1) (ca. 1100 mAh g(C) (-1)). X-ray diffraction and scanning electron microscope analysis reveal that this excellent rechargeability is based on the reversible formation and decomposition of toroid-shaped lithium peroxide. Therefore, the uniform distribution of ultrafine IrO2 particles, with extraordinary OER catalytic activity, on KB carbon enables the IrO2/KB to be a promising electrocatalyst for Li-O-2 batteries.