Highly porous carbons from hydrochar by means of a controlled physical activation process and their hydrogen storage performance

Highly porous carbons with surface areas approaching 3300 m 2 g −1 have been synthesized from eucalyptus sawdust and pistachio shells through controlled CO 2 activation. The implementation of hydrothermal carbonization increases the global yield of the synthesis process and decreases the reactivity toward CO 2 by decreasing the density of structural defects and removing virtually all the mineral matter contained in the residues. The last feature is a determining factor in porosity generation efficiency. Thereby, activation proceeds under chemical control, ensuring the uniform generation of porosity inside the particles, which leads to materials with relatively narrow pore size distributions in the micro-to small mesopore region (<3.5 nm). These materials store significant amounts of H 2 at −196 °C/100 bar, reaching up to 9.8 wt%. Theoretical calculations show that the most energy-efficient way of storing H 2 is using a TPSA system, which allows the working capacities to be substantially enhanced up to 9.7 wt%.