Record hydrogen storage capacities in advanced carbon storage materials

Abstract

Carbons can be engineered to achieve exceptional storage capacities: the ALL-CRAFT (www.all-craft.missouri.edu) nanoporous carbon achieves gravimetric excess adsorption of 0.073 kg H2/kg C, gravimetric storage capacity of 0.106 kg H2/kg C, and volumetric storage capacity of 0.040 kg H2/l C (80 K, 100 bar). The nanopores generate high storage capacity by having: high surface area (2,600 m^2/g); high H2-wall interaction; and multi-layer H2 adsorption (cryogenic). We we show how the experimental characteristics of the ALL-CRAFT carbon correlate to the observed H2 storage, with help from theoretical considerations and GCMC simulations. The ALL-CRAFT carbon is composed of a large variety of pore sizes which generates substantial heterogeneity. We explain most features observed by considering superpositions of low- and high-binding energy sites (9 kJ and 5 kJ/mol), corresponding to wide and narrow (< 1 nm) pores. We further explain: exceptional low-temperature storage (in excess of the usual Chahine's rule); and absence of an excess adsorption peak (for 0 < P < 100 bar)