Headwaters Technology Innovation Shows Hydrogen Storage Using Porous Carbon Nanospheres

FIG. 1 is a high resolution TEM image of a carbon nanomaterial for storing hydrogen  

 Headwaters Technology Innovation, LLC (Lawrenceville, NJ) received U.S. Patent 7,670,588 for a method of hydrogen storage using porous carbon nanospheres

Hydrogen is stored by adsorbing the hydrogen to a carbon nanomaterial that includes carbon nanospheres. The carbon nanospheres are multi-walled, hollow carbon nanostructures with a maximum diameter in a range from about 10 nm to about 200 nm. The nanospheres have an irregular outer surface and an aspect ratio of less than 3:1. The carbon nanospheres can store hydrogen in quantities of at least 1.0% by weight, according to inventors Bing Zhou and Cheng Zhang

The physical and chemical properties of the carbon nanospheres provide advantages for storing hydrogen as compared to carbon nanotubes and other carbon based materials that have been used to store hydrogen.

The carbon nanospheres are typically multi-walled, hollow carbon nanostructures with a maximum diameter in a range from about 10 nm to about 200 nm. Typically the nanospheres have an aspect ratio of less than about 3:1 (i.e., width to height is less than 3:1), preferably less than about 2:1, more preferably less than about 1.75:1, and most preferably less than about 1.5:1. In one embodiment, the carbon nanospheres have an irregular surface. The irregular surface has graphitic defects that cause the nanospheres to have a shape that is not perfectly spherical. The graphitic defects are believed to contribute to the ability to store hydrogen and/or to achieve a desired surface functionalization, which can also contribute to hydrogen storage. The carbon nanospheres are highly graphitic, which gives the carbon nanomaterial excellent electrical and thermal conductivity. The highly graphitic nature is also very beneficial for hydrogen storage.

The size and shape of the carbon nanospheres is particularly advantageous for storing hydrogen. The carbon nanospheres of the invention have a large surface area available for adsorbing hydrogen. In one embodiment, the surface area is in a range from about 80 m.sup.2/g to about 400 m²/g, more preferably about 120 m²/g to about 300 m²/g, and most preferably about 150 m²/g about 250 m²/g. The closed structure is also partially responsible for the high surface area. The hollowness of the nanospheres can be advantageous because the hollow portion reduces the weight of the carbon nanomaterial while having a comparatively less deliterious effect on hydrogen storage compared to the open hollow center of carbon nanotubes.

The multi-walled nature of the graphitic structure provides multiple layers for storing hydrogen and provides narrow spacing between the individual graphite sheets or layers for storing hydrogen. Because the nanospheres are a closed structure, the carbon nanospheres do not have macro pores for hydrogen to flow through, which can improve hydrogen storage. The spheroidal shape and multi-walled nature of the carbon nanospheres also provides strength that makes the carbon nanospheres less likely to be crushed or broken into undesired shapes or non-shaped graphite. Maintaining the shape of the carbon nanospheres can be important for maintaining performance characteristics over time (e.g. adsorption and reversibility of adsorption). The multi-walled nature of the nanospheres also allows the surface to be functionalized while maintaining the beneficial thermal and electrical conductivity via the interior graphite layers. 

FIG. 2A is a high resolution SEM image of an intermediate carbon material, which includes a plurality of nanosphere clusters;

FIG. 2C is a high resolution TEM image of the carbon nanomaterial of FIG. 2A showing a plurality of carbon nanostructures agglomerated together and revealing the multi-walled and hollow nature of the carbon nanostructures that form a cluster;

FIG. 4 is a high resolution TEM image showing a close up of a carbon nanostructure that has a catalytic templating nanoparticle in its center.