Optimization of biomass-based carbon materials for hydrogen storage

Abstract Hydrogen is considered as the most promising future fuel, as its combustion generates only water vapor besides energy. However, finding efficient, safe and low cost storage methods is the basic impediment for the adoption of hydrogen as fuel. For this purpose, five biomass-based carbon samples have been successfully prepared through KOH activation procedure. The microstructure of the prepared materials was tuned by varying KOH/precursor weight ratio from 1:1 to 5:1, in order to optimize their hydrogen storage behavior and to clarify the storage mechanism. A careful textural and morphological characterization of the prepared samples (N 2 and CO 2 adsorption, X-ray diffraction, electron microscopy observations) showed that by increasing the activation ratio the nature of the carbons changes from microporous to micro-mesoporous. Thus, an increase in the surface area was observed which enhanced H 2 sorption capacity when high H 2 pressures were adopted. At subatmospheric pressure, the role of active sites for H 2 adsorption, located in the oriented graphene sheets, was clearly elaborated. Finally, the optimal carbon sample has shown a capacity of 6 wt% and 1.22 wt% at −196 °C and 25 °C respectively, and 200 bar. These results make biomass-based carbons promising materials for H 2 storage application.