3D honeycomb microstructure morphology of porous PbO₂-graphite tablet towards catalyzing the [VO]²⁺/[VO₂]⁺ reaction for vanadium redox flow battery

A novel and low-cost porous graphite tablet deposited with lead oxide (porous PbO₂-graphite tablet) was investigated as an appropriate positive electrode for catalyzing the [VO]²⁺/[VO₂]⁺ reaction in vanadium redox flow battery. Porous PbO₂-graphite tablet was fabricated using uniform mixing of zinc-metal powder with graphite powder, pressing of previously mixed powder under optimized pressure followed by treatment in H₂SO₄ solution for leaching out of zinc from graphite bulk and finally electrodeposition of PbO₂ onto previously porous graphite tablet. Micrographs from the scanning electron microscopy showed morphology of 3D Honeycomb nanostructure with high surface area. Electrochemical studies exhibited the optimized porous PbO₂-graphite tablet possesses an acceptable electrochemical performance in terms of peak current densities, Ohmic resistance, kinetic reversibility, and appropriate stability after repetitive 50-cycle testing towards the [VO]²⁺/[VO₂]⁺ redox reaction. These results can be attributed to the synergistic effect between graphite and PbO₂ with appropriate electrocatalytic nature, highly accessible surface area of the tablet, and good electrical conductivity which enhances electron transfer rate.