Encapsulation of hydrogen in nanoporous carbon after high-pressure loading

Abstract

High hydrogen storage in the matrix has always been regarded as the goal for energy applications. However, the exploration of the hydrogen storage material should concentrate on not only the maximum of the hydrogen storage but also the residual apart of the hydrogen under the ambient conditions after the benefit conditions. Herein, the center of this research is the releasing ability of the solid matrix under ambient conditions, aimed at further the utilization in various situations. Nanoporous carbon (NPC) fabricated via alkali-activation from rice husk was chosen as an adsorbent, considered a promising, safer, convenient hydrogen gas delivery technology. Their textural properties, such as porosity and specific surface area, were evaluated to connect with the amount of hydrogen released in water. These carbon materials possess a high specific surface area of up to 3000 m²/g and large pore volumes of up to 3.03 cm³/g, with a typical hysteresis exhibited between the adsorption and desorption isotherms after the activation. Furthermore, NPC holds an excellent hydrogen storage ability of 2.96–3.12 wt % at 0.1 MPa, 77 K. 0.89 % of the residual hydrogen was entrapped in NPC after being loaded at the pressure of 12 MPa, with the maximum amount released of 6500 ppm (1.4 × 10⁻³ wt %). A close relationship between hydrogen releasing ability and these textural properties was exhibited. The development of porosity and specific surface area caused by activation appears to optimize the entrapment of hydrogen not only under the pressurization but also after pressure off-loaded.