A hydrogen fuel cell uses hydrogen as the fuel, and utilizes the reaction between hydrogen and oxygen to produce electricity. In order to reduce cell cost and develop hydrogen fuel cell, the key is to increase hydrogen storage sufficiently. A research team from University of Michigan chose three compounds among 500,000 materials for their usable hydrogen capacities.

This team of researchers from the University of Michigan has great expectations for metal-organic framework (MOF). They identified methods to cram more hydrogen into small storage structure (MOF), so that in the future hydrogen fuel cell can increase energy density and reach a longer cell life. In particular, MOF's porous nature is promising in carbon capture, electrode materials, and catalyst materials.

Metal organic frameworks (MOF) are materials of metal ions coupled with organic molecules. Its porous nature and high "specific surface area" can store large quantities of hydrogen efficiently. Researchers put together nearly 500,000 MOFs' data into one database, including those that were previously constructed and those that are hypothetical. The question is how to identify the ideal compounds among the numerous MOFs?

To accelerate the progress of searching for the optimal materials, the Michigan researchers used high-throughput computer simulations to screen nearly 500,000 MOFs, so as to accelerate the progress of searching for optimal materials. Then the scientists design the structure of the potential MOF.

The team uses Chahine rule to screen the H2 absorption capacities of 493,458 types of MOFs under some conditions of air pressure and temperature. Then, with Grand Canonical Monte Carlo (GCMC) method to analyze 43,777 types of MOF candidates' capacity trends.

Among the nearly 500,000 MOFs, three candidates were chosen. The researchers constructed or synthesized these materials, and tested their hydrogen storage capacity. Don Siegel, U-M associate professor of Materials Engineering, expressed that the energy density of these MOFs are higher than the past designs. Their properties allow future scientists to make smaller, lighter, and higher capacity cells.

The three MOFs are named as SNU-70, UMCM-9, and PCN-610/NU-100. This research team published their work in Nature Communications. The performance of the three exceeded the past records.

However, the Michigan researchers didn't manufacture the new type of Hydrogen fuel cells, so the specific benefits of the new materials to the fuel cells are still unknown.

The hydrogen fuel cell is at the heart of a hydrogen fuel cell vehicle, and is the major cost. When the research team successfully makes next-generation hydrogen fuel cells, costs of hydrogen fuel cell will be lowered.

(Collaborative media: TechNews; Photo credit: University of Michigan)