RuO2 nanoparticles supported on MnO2 nanorods as high efficient bifunctional electrocatalyst of lithium-oxygen battery

• Published in: Nano energy 2016-10, Vol.28 (C), p.63-70
• Main Authors: Xu, Yue-Feng, Chen, Yuan, Xu, Gui-Liang, Zhang, Xiao-Ru, Chen, Zonghai, Li, Jun-Tao, Huang, Ling, Amine, Khalil, Sun, Shi-Gang
• Format: Article
• Language: English
• Subjects: Bifunctional electrocatalysts; Lithium-oxygen battery; OER; ORR; RuO2 nanoparticles on MnO2 nanorods
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2016.08.009

RuO2 nanoparticles supported on MnO2 nanorods (denoted as np-RuO2/nr-MnO2) were synthesized via a two-step hydrothermal reaction. SEM and TEM images both illustrated that RuO2 nanoparticles are well dispersed on the surface of MnO2 nanorods in the as-prepared np-RuO2/nr-MnO2 material. Electrochemical results demonstrated that the np-RuO2/nr-MnO2 as oxygen cathode of Li–O2 batteries could maintain a reversible capacity of 500mAhg−1 within 75 cycles at a rate of 50mAg−1, and a higher capacity of 4000mAhg−1 within 20 cycles at a rate as high as 200mAg−1. Moreover, the cell with the np-RuO2/nr-MnO2 catalyst presented much lower voltage polarization (about 0.58V at a rate of 50mAg−1) than that measured with only MnO2 nanorods during charge/discharge processes. The catalytic property of the np-RuO2/nr-MnO2 and MnO2 nanorods were further compared by conducting studies of using rotating disk electrode (RDE), chronoamperommetry and linear sweep voltammetry. The results illustrated that the np-RuO2/nr-MnO2 exhibited excellent bifunctional electrocatalytic activities towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Furthermore, in-situ high-energy X-ray diffraction was employed to trace evolution of species on the np-RuO2/nr-MnO2 cathode during the discharge processes. In-situ XRD patterns demonstrated the formation process of the discharge products that consisted of mainly Li2O2. Ex-situ SEM images were recorded to investigate the morphology and decomposition of the sphere-like Li2O2, which could be observed clearly after discharge process, while are decomposed almost after charge process. The excellent electrochemical performances of the np-RuO2/nr-MnO2 as cathode of Li–O2 battery could be contributed to the excellent bifunctional electrocatalytic activities for both the ORR and OER, and to the one-dimensional structure which would benefit the diffusion of oxygen and the storage of Li2O2 in the discharge process of Li–O2 battery. [Display omitted] •The np-RuO2/nr-MnO2 were firstly synthesized via a two-step hydrothermal reaction.•The np-RuO2/nr-MnO2 as cathode of Li–O2 battery exhibits high bifunctional electrocatalytic activity.•In-situ synchrotron HEXRD illustrated the formation process of Li2O2.