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.