Los Alamos National Laboratory and University of Alabama researchers have come up with a new method for recycling hydrogen-containing fuel materials, which could open the door to economically viable hydrogen-based vehicles. The researchers worked within DOE’s Chemical Hydrogen Storage Center of Excellence.
Ideally, a fuel should be lightweight to maintain overall fuel efficiency, and pack a high energy content into a small volume. Unfortunately, under normal conditions, pure hydrogen has a low energy density per unit volume - presenting technical challenges for its use in vehicles capable of travelling 300 miles or more on a single fuel tank (a benchmark target set by DOE).
In order to overcome some of the energy density issues associated with pure hydrogen, work within the Chemical Hydrogen Storage Center of Excellence has focused on using a class of materials known as chemical hydrides. Hydrogen can be released from these materials and potentially used to run a fuel cell. These compounds can be thought of as “chemical fuel tanks” because of their hydrogen storage capacity.
Ammonia borane is an attractive example of a chemical hydride because its hydrogen storage capacity approaches 20 percent by weight. The main drawback of ammonia borane has been the lack of energy-efficient methods to reintroduce hydrogen back into the spent fuel once it has been released. Until recently, after hydrogen release, ammonia borane couldn’t be adequately recycled.
Los Alamos and University of Alabama researchers have been developing methods for the efficient recycling of ammonia borane. The team made a breakthrough when it discovered that a specific form of dehydrogenated fuel, called polyborazylene, could be recycled with relative ease using modest energy input. This development is a significant step toward using ammonia borane as a possible energy carrier for transportation purposes.
“This research represents a breakthrough in the field of hydrogen storage and has significant practical applications,” said Dr. Gene Peterson, leader of the Chemistry Division at Los Alamos. “The chemistry is new and innovative, and the research team is to be commended on this excellent achievement.”
The team is currently working with colleagues at The Dow Chemical Company, another Center partner, to improve overall chemical efficiencies and move toward large-scale implementation of hydrogen-based fuels within the transportation sector.