Papyrus-derived cathode materials for quasi-solid aluminum–air batteries

The production of sustainable materials to be used in electrochemical energy conversion and storage devices based on oxygen reduction reaction (ORR), such as fuel cells, electrolysers and metal-air batteries, is a key topic in many strategic sectors. To date, the cathode materials used for these devices typically include expensive catalysts made from noble metal nanoparticles. Therefore, much research is being devoted to producing cheaper and, if possible, environmentally friendly cathode materials. Here we report the production of biomass-derived carbonaceous materials that can be used as effective cathode material in metal-air cells. In particular, the carbonaceous materials were obtained by proper treatments of raw papyrus biomass (pyrolysis and N-doping). Papyrus is a marsh plant, invasive in many regions of the world. Thus, it could produce large amounts of readily available biomass that could be used for various applications. The cheap papyrus-derived cathodes were tested under practical conditions in aluminum-air cells using solid biopolymer as electrolytes (xanthan hydrogels) and showed superior electrochemical performances in ORR compared to commercial platinum-based cathodes. The results obtained on papyrus carbonaceous materials demonstrate the possibility to realize aluminum-air batteries made with natural raw materials (xanthan hydrogels as electrolytes and biomass-derived cathodes), as a very promising solution for eco-sustainable energy conversion and storage devices.