Preparation of nanocellulose-based nitrogen-doped carbon aerogel electrocatalysts through hydrothermal pretreatment for zinc-air batteries

Cellulose nanofiber (CNF) is an environmentally friendly material with a high specific surface area, which is an ideal candidate for cathode catalysts in zinc-air batteries (ZABs). However, untreated CNF-based carbon materials suffer from low intrinsic activity and fewer micro-mesopores. Herein, we developed an N-doped porous carbon aerogel from CNF and graphite phase carbon nitride (g-C3N4) via hydrothermal pretreatment and the carbonization process. The CNF can serve as the skeleton of the aerogel that leads to an interconnected porous structure, while g-C3N4 guarantees the in situ N doping and the formation of more nanopores. Therefore, the as-prepared carbon aerogel exhibits excellent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performances owing to the successful N doping with sufficient graphite-N and pyridine-N active sites (69.1%) and high specific surface areas (785.4 m2 g-1). The assembled ZABs with a carbon aerogel deliver a specific capacity of 790 mA h g-1 and an energy density of 945.6 W h kg-1 with a long-term stability over 100 h. This work opens a new avenue for the effective conversion of abundant biomass into bifunctional air cathodes for energy-related applications. A cellulose-based nitrogen-doped carbon aerogel with abundant micro-mesopores for zinc-air batteries with high open-circuit voltage and long cycle stability was prepared by hydrothermal pretreatment and simple carbonization.