Abstract.A survey is presented of the storage capacities of a large number of different adsorbents for hydrogen at 77 K and 1 bar. Results are evaluated to examine the feasibility and perspectives of transportable and reversible storage systems based on physisorption of hydrogen on adsorbents. It is concluded that microporous adsorbents, e.g. zeolites and activated carbons, display appreciable sorption capacities. Based on their micropore volume (∼ 1 ml/g) carbonbased sorbents display the largest adsorption, viz. 238 ml (STP)/g, at the prevailing conditions. Optimization of sorbent and adsorption conditions is expected to lead to adsorption of ∼ 560 ml (STP)/g, close to targets set for mobile applications. In the last two decades there has been an increasing interest in the development of (transportable) reversible systems for hydrogen storage with a high capacity, which is critical to the large-scale application of hydrogen fuel cells, in particular for mobile applications [1]. Up to now focus has mostly been on liquid-hydrogen and metal-hydride systems, which both have low energy efficiencies [2]. A higher energy efficiency is attainable with systems in which hydrogen is concentrated by physical adsorption above 70 K using a suitable adsorbent [3][4][5]. Such an absorbent should be safe, light and cheap and of course have a high adsorption capacity. In order to obtain a suitable driving range for automotive applications the United States Department of Energy (DOE) target has been set to 6.5 wt %, which equals 720 ml (STP)/g adsorbent . Schwarz and co-workers [6-8] studied the applicability of molecularly engineered activated carbons and came up with promising results. Much excitement has arisen on recent reports on the use of carbon nanofibers [9] and carbon nanotubes [10,11] In this paper we present a survey of the storage capacity for hydrogen at 77 K and 1 bar of a large number of different types of adsorbents -silicas, aluminas, zeolites, graphite, activated carbons and carbon nanofibers -in a wide range of specific surface areas and of different textures, in order to give further direction to our research on the development of a suitable storage system. PACS

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