Fabrication of hierarchical porous carbon for oxygen reduction reaction by selective hydrolysis of hemicelluloses and lignin from eucalyptus wood

As a wood containing many ordered cell cavities and blood vessels, eucalyptus is an ideal precursor material in preparing hierarchical porous carbon electrodes for Zn-air batteries. However, insufficient micro-mesoporous and minor active sites inhibit the application of wood-directly derived carbon materials in Zn-air batteries. Hence, a simple and cost-effective formic acid pretreatment method was proposed to prepare nitrogen-doped bulk phase catalysts with abundant micro-mesoporous and enough high active sites from eucalyptus. Formic acid pretreatment selectively removed part of lignin and hemicelluloses, thus generating abundant nanopores and contributing to the introduction of more nitrogen active sites. Moreover, the obtained bulk carbon had high mechanical strength and wonderful electrical conductivity, containing cross-linked networks and natural ion transport channels. Benefiting from the above advantages, the bulk carbon catalyst could be directly used as self supported cathode, and the resulting Zn-air batteries achieved a long cycle life of more than 300 h. This work provides a simple and feasible method for the development of biomass-derived hierarchical bulk-phase porous carbons for energy-related applications.

Automated summary

This study proposes a simple and cost-effective formic acid pretreatment method to prepare nitrogen-doped bulk-phase carbon catalysts from eucalyptus. The pretreatment selectively removes lignin and hemicelluloses, generating abundant nanopores and introducing nitrogen active sites. The obtained bulk carbon catalyst has high mechanical strength and excellent electrical conductivity, making it suitable for use as a self-supported cathode in Zn-air batteries. The resulting batteries exhibit a long cycle life of over 300 hours.