Acta’s catalyst synthesis by polymer templation. Click to enlarge.

Acta uses a patented approach to producing its catalysts, involving a templating polymer that organizes the catalyst metals during application to the substrate. The polymer structure prevents agglomeration of the very small particle sizes used, resulting in a large active area. Any metal combination can be used in the process, according to Acta.

Acta is targeting its catalysts at a range of applications, including fuel cells, water and ammonia electrolysis, fuel reforming, and process catalysts.

In a 2005 paper in the Journal of Power Sources, Dr. Gerardine Botte, associate professor of Chemical and Bio-Molecular Engineering at the Russ College of Engineering and Technology at Ohio University and her colleagues laid out an argument for using ammonia electrolysis for hydrogen production. (Earlier post.)They subsequently licensed their catalytic ammonia electrolyzer technology to American Hydrogen Corporation for commercialization.

In many ways, ammonia is an excellent hydrogen carrier; liquid ammonia represents a convenient way of storing supplies of hydrogen, boasting a specific energy density(kWhL^-1) 50%higher than liquefied hydrogen. Ammonia is also easily condensed at ambient temperature (under 8 bar of pressure), which makes it a good choice for transportation and storage. Even though ammonia is flammable within defined limits (16.25% by volume in the air) and toxic (above 25 ppm), its presence can be detected by its characteristic odor (above 5 ppm). Ammonia is produced worldwide in large quantities (more than 100 million ton year^-1), which allows the effect of economy of scale on the cost of production. Its decomposition by electrooxidation in alkaline media at low overpotentials is NO_x and CO_x free with nitrogen and water as products of reaction.

—Vitse et al. (2005)

Ammonia electrolysis couples the ammonia electro-oxidation reaction with the hydrogen evolution reaction for the production of high-purity hydrogen in an alkaline electrolytic cell. The reactions are as follows:

2NH₃(aq) + 6OH^-→N₂(g) + 6H₂O + 6e^- (1)

6H₂O + 6e^-→3H₂(g) + 6OH^- (2)

The overall reaction is:

2NH₃(aq)→N₂(g) + 3H₂(g) (3)

An ammonia cylinder at 10 bar contains more hydrogen per kg or per liter than any current hydrogen storage system—hydrogen stored in a 700 bar compressed gas cylinder, in a liquid hydrogen tank, or in a metal hydride tank.

The results of [our] study indicate that the production of hydrogen by the electrolysis of ammonia is a promising technology as the thermodynamics is in favor of the reaction; however, the commercialization of the technology depends on the development of effective electrodes for the electro-oxidation of ammonia. Therefore, future work on this area should be focus on the development of electrodes to decrease the overpotential of this reaction.

—Vitse et al. (2005)

Acta said that it has a number of customers now sampling its ammonia reforming technology and sees growing interest in the use of ammonia as a fuel.

Resources

• Frédéric Vitse, Matt Cooper, Gerardine G. Botte (2005) On the use of ammonia electrolysis for hydrogen production, Journal of Power Sources 142 (2005) 18–26 doi: 10.1016/j.jpowsour.2005.07.004

• Acta and HYPERMEC: A Breakthrough Catalyst Technology (2006)