Hydrogen and methane storage in adsorbent materials for automotive applications

A huge obstacle to replacing gasoline as the main energy carrier in automotive applications is the relatively low energy density of suitable replacements. Gaseous energy carriers must be stored at high pressure or very low temperature in order to obtain an energy density suitable for vehicular use. High pressure gas storage requires large, cylindrical containers that occupy large amounts of cargo of passenger space. On the other hand, low-temperature storage requires expensive, heavy cooling systems to keep the gas in a liquid or high-density gaseous state. Adsorbent materials are becoming an attractive option to solve the energy density problem. Porous materials with a high surface area to volume ratio are desirable because of the large number of adsorption sites per volume of adsorbent, and, to this end, much research has focused on porous carbons and metal-organic frameworks. Research into adsorbent materials has focused on increasing the specific surface area, increasing the adsorption energy, and optimizing the pore structure. Here, we review current progress in adsorbent materials' development and discuss challenges in moving from laboratory scale to full-scale implementation including material packing and compatibility. In particular, we discuss the difference between using a material's crystal density and its bulk density to characterize gas storage and give estimates for the performance of current benchmark materials in an 8 gallon gasoline equivalent storage system. Copyright (c) 2015 John Wiley & Sons, Ltd.