Synopsis of Factors Affecting Hydrogen Storage in Biomass-Derived Activated Carbons

Hydrogen (H 2 ) is largely regarded as a potential cost-efficient clean fuel primarily due to its beneficial properties, such as its high energy content and sustainability. With the rising demand for H 2 in the past decades and its favorable characteristics as an energy carrier, the escalating USA consumption of pure H 2 can be projected to reach 63 million tons by 2050. Despite the tremendous potential of H 2 generation and its widespread application, transportation and storage of H 2 have remained the major challenges of a sustainable H 2 economy. Various efforts have been undertaken by storing H 2 in activated carbons, metal organic frameworks (MOFs), covalent organic frameworks (COFs), etc. Recently, the literature has been stressing the need to develop biomass-based activated carbons as an effective H 2 storage material, as these are inexpensive adsorbents with tunable chemical, mechanical, and morphological properties. This article reviews the current research trends and perspectives on the role of various properties of biomass-based activated carbons on its H 2 uptake capacity. The critical aspects of the governing factors of H 2 storage, namely, the surface morphology (specific surface area, pore volume, and pore size distribution), surface functionality (heteroatom and functional groups), physical condition of H 2 storage (temperature and pressure), and thermodynamic properties (heat of adsorption and desorption), are discussed. A comprehensive survey of the literature showed that an “ideal” biomass-based activated carbon sorbent with a micropore size typically below 10 Å, micropore volume greater than 1.5 cm 3 /g, and high surface area of 4000 m 2 /g or more may help in substantial gravimetric H 2 uptake of >10 wt% at cryogenic conditions (−196 °C), as smaller pores benefit by stronger physisorption due to the high heat of adsorption.