Hierarchical Ru- and RuO2-foams as high performance electrocatalysts for rechargeable lithium–oxygen batteries
The structural design and synthesis of cathode materials with superior catalytic activity is still a major challenge for rechargeable lithium–oxygen batteries. Here we prepared hierarchical Ru- and RuO2-foams as binder- and carbon-free electrocatalysts via an electrodeposition process using a hydrogen bubble template. The as-prepared Ru- and RuO2-foams were grown vertically on stainless steel mesh, with a dendritic bracken-like structure and highly divided thin branches. These freestanding Ru- and RuO2-foams provide high catalytic activity, large space to accommodate the discharge products, short ion diffusion lengths and channels for rapid transport of oxygen and electrolytes. The hierarchically dendritic cathodes without carbon and binders present low charge/discharge overpotential, remarkable cyclability, good oxygen efficiency and reduced irreversible formation/decomposition. The excellent performance of these foams, as characterized by systematic analysis and the facile fabrication approach provide an alternative method to develop advanced cathodes for Li–O2 batteries.