Hierarchical porous carbon toward effective cathode in advanced zinc-cerium redox flow battery

Advanced zinc-cerium redox flow battery（ZCRFB） is a large-scale energy storage system which plays a significant role in the application of new energy sources. The requirement of superior cathode with high acitivity and fast ion diffusion is a hierarchical porous structure, which was synthesized in this work by a method in which both hard template and soft template were used. The structure and the performance of the cathode prepared here were characterized and evaluated by a variety of techniques such as scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, X-ray photoelectron spectroscopy（XPS）, cyclic voltammetry（CV）, linear sweep voltammetry（LSV）, and chronoamperometry（CA）. There were mainly three types of pore size within the hierarchical porous carbon： 2 μm, 80 nm, and 10 nm. The charge capacity of the cell using hierarchical porous carbon（HPC） as positive electrode was obviously larger than that using carbon felt; the former was 665.5 mAh with a coulombic efficiency of 89.0% and an energy efficiency of 79.0%, whereas the latter was 611.1 mAh with a coulombic efficiency of 81.5% and an energy efficiency of 68.6%. In addition, performance of the ZCRFB using HPC as positive electrode showed a good stability over 50 cycles.These results showed that the hierarchical porous carbon was superior over the carbon felt for application in ZCRFB.