Chemical fuel tanks

A new method for hydrogen storage using materials known as chemical hydrides could make fuel-cell vehicles more economically viable.

The technique is currently being researched by scientists at Los Alamos National Laboratory, the University of Alabama and the US Department of Energy’s Chemical Hydrogen Storage Center of Excellence.

The team believes chemical hydrides can be used as ‘chemical fuel tanks’ to store hydrogen. These compounds could then release hydrogen that could be used to run a fuel cell.

The researchers also believe these chemical hydrides could overcome some of the energy density issues associated with pure hydrogen.

Under normal conditions, pure hydrogen has a low energy density per unit volume. This means it cannot currently be used in vehicles capable of travelling 300 miles or more on a single fuel tank - a benchmark target set by the US Department of Energy.

The researchers found that ammonia borane is an attractive example of a chemical hydride because its hydrogen storage capacity is close to 20 per cent by weight. The chief drawback of ammonia borane, however, has been the lack of energy-efficient methods to reintroduce hydrogen back into the spent fuel once it has been released.

Los Alamos and University of Alabama researchers believe they might have solved the problem with a new method for efficiently recycling ammonia borane. The team discovered that a specific form of dehydrogenated fuel, called polyborazylene, could be recycled with relative ease using modest energy input.

Gene Peterson, leader of the chemistry division at Los Alamos, said this development is a significant step toward using ammonia borane as a possible energy carrier for transportation purposes.

The research team is currently working with colleagues at The Dow Chemical Company to improve overall chemical efficiencies and move toward large-scale implementation of hydrogen-based fuels within the transportation sector.