Oxygen-rich microporous carbons with exceptional hydrogen storage capacity

Abstract

Porous carbons have been extensively investigated for hydrogen storage but, to date, appear to have an upper limit to their storage capacity. Here, in an effort to circumvent this upper limit, we explore the potential of oxygen-rich activated carbons. We describe cellulose acetate-derived carbons that combine high surface area (3800 m ² g ⁻¹) and pore volume (1.8 cm ³ g ⁻¹) that arise almost entirely (>90%) from micropores, with an oxygen-rich nature. The carbons exhibit enhanced gravimetric hydrogen uptake (8.1 wt% total and 7.0 wt% excess) at −196 °C and 20 bar, rising to a total uptake of 8.9 wt% at 30 bar, and exceptional volumetric uptake of 44 g l ⁻¹ at 20 bar, and 48 g l ⁻¹ at 30 bar. At room temperature they store up to 0.8 wt% (excess) and 1.2 wt% (total) hydrogen at only 30 bar, and their isosteric heat of hydrogen adsorption is above 10 kJ mol ⁻¹.

Abstract

Hydrogen is attractive as a clean fuel for motor vehicles and porous carbons represent promising hydrogen storage materials. Here, Mokaya and colleagues incorporate oxygen-rich functional groups into porous carbons with high microporosity, showing that such materials exhibit significantly enhanced H ₂ storage capacity.