Synthesis of ordered mesoporous NiCo 2 O 4 via hard template and its application as bifunctional electrocatalyst for Li-O 2 batteries

Ordered mesoporous NiCo2O4 (OM NiCo2O4) materials have been synthesized via KIT-6 template and used as bifunctional electrocatalyst for rechargeable Li-O2 batteries. Characterization of the catalyst by X-ray diffractometry and transmission electron microscopy confirms the formation of a single-phase, 3-dimensional, ordered mesoporous NiCo2O4 structure. The as-prepared OM NiCo2O4 exhibits a specific surface area of 95.5 m2g−1 with mesoporous peaks between 3 and 5nm. Linear scanning voltammetric measurements reveal that OM NiCo2O4 exhibits slightly higher catalytic activity for the oxygen reduction reaction but much higher activity for the oxygen evolution reaction than Ketjen black (KB) carbon. The Li-O2 battery utilizing OM NiCo2O4 shows a slightly higher discharge voltage plateau and a higher specific capacity of 4120 mAh g−1 than that with pure KB, and the subsequent charge voltage is much lower than that with KB. Moreover, an enhanced cyclability of Li-O2 battery with OM NiCo2O4 cathode is observed with a capacity retention ratio of 65.4% after 5 cycles. When restricting the discharge capacity at 1000 mAh g−1, Li-O2 battery with OM NiCo2O4 cathode shows an improved cyclability and the cut-off voltage is as high as 2.4V after 20 cycles, suggesting that OM NiCo2O4 could be as a promising catalyst for Li-O2 batteries.