Innovative methods to couple earth-abundant biomass waste with air batteries

Metal–air batteries are promising candidates to provide green and sustainable energy sources with low cost and high energy density. However, the commercialization of metal–air batteries is mainly hampered by the expensive precious metal catalysts, which are necessarily used for oxygen reduction and evolution reactions within the air cathodes. Biomass waste, the earth-abundant renewable energy source, can play an intriguing role in generating high-performance and low-cost carbon-based electrocatalysts for air batteries. This mini review presents the latest advances on innovative processing strategies of diverse biomass waste sources into various carbon-based electrocatalysts, whose performance are comparable with or even can beat that of the noble metal catalysts. Furthermore, how the composition and structure of the biomass waste is related to the electrochemical performances of the resultant electrocatalysts for air batteries is discussed. This mini review offers the rational principles and strategies to upcycle biomass waste into value-added materials for energy storage and conversion application.