Tailoring three dimensional α–MnO2/RuO2 hybrid nanostructure as prospective bifunctional catalyst for Li–O2 batteries

Abstract We have synthesized three dimensional architectural α–MnO 2 /RuO 2 hybrid nanostructures with three different compositions of (75:25), (69:31) and (50:50) by hydrothermal approach and evaluated their bifunctional electrocatalytic activity for Li–O 2 battery applications. The morphology of the α–MnO 2 /RuO 2 nanostructures changed from sharp sea urchins to solid nanospheres with increasing RuO 2 content in the composition. The variations observed in physical, structural, morphological and electrochemical properties were characterized with respect to the MnO 2 /RuO 2 concentrations by step by step analyses. MnO 2 exhibited better ORR catalytic activity, while RuO 2 revealed superior OER catalytic activity. Among the concentrations investigated, α–MnO 2 :RuO 2 (75:25) exhibited superior catalytic activity for oxygen reduction and evolution reactions in aqueous media. This excellent catalytic activity logically led us to apply it as air-cathode catalyst in Li–O 2 cell, which produced a maximum capacity of >8100 mAh g −1 with high columbic efficiency and cyclability. The superior performance of the hybrid nanostructure is mainly attributed to its structural and compositional design which favors the electrochemical activity. Based on a careful investigation on the structural characterizations, the growth mechanism of the 3D nanostructured α–MnO 2 /RuO 2 mixed oxides is discussed in detail.