A research team led by Northwestern University has designed and synthesized new materials with ultra-high porosity and surface area for the storage of hydrogen and natural gas for vehicles.
The designer materials, a type of a metal-organic framework (MOF), can store significantly more gas than conventional adsorbent materials at much safer pressures and at much lower costs.
“We’ve developed a better onboard storage method for hydrogen and methane gas for next-generation clean energy vehicles,” says Omar K. Farha, who led the research.
“To do this, we used chemical principles to design porous materials with precise atomic arrangement, thereby achieving ultra-high porosity,” he adds.
Adsorbents are porous solids that bind liquid or gaseous molecules to their surface. Thanks to its nanoscopic pores, a one-gram sample of the Northwestern material (with a volume of six M&Ms) has a surface area that would cover 1.3 football fields.
The new materials also could be a breakthrough for the gas storage industry at large, Farha says, because many industries and applications require the use of compressed gases such as oxygen, hydrogen, methane and others. The ultra-porous MOFs, named NU-1501, are built from organic molecules and metal ions or clusters that self-assemble to form multidimensional, highly crystalline, porous frameworks.
Hydrogen- and natural gas-powered vehicles currently require high-pressure compression to operate. The pressure of a hydrogen tank is 300 times greater than the pressure in car tires. Because of hydrogen’s low density, it is expensive to accomplish this pressure, and it also can be unsafe because the gas is highly flammable.
Developing new adsorbent materials that can store gas onboard vehicles at much lower pressures can help scientists and engineers reach U.S. Department of Energy targets for developing the next generation of clean energy automobiles.
To meet these goals, both the size and weight of the onboard fuel tank need to be optimized. The highly porous materials in this study balance both the volumetric (size) and gravimetric (mass) deliverable capacities of gas, bringing researchers one step closer to attaining these targets.
Photo: The molecular structure of the NU-1501 material