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Experimental and economic study of aluminium-gallium alloys as a fuel/catalyst for hydrogen propulsion

2009-08-12, Keane, Eamon, Browne, David J., Carr, A. J. (Alun J.)

An investigation was carried out into the feasibility of using Al-Ga alloys as a renewable agent to produce hydrogen from water, following positive claims from a research group in the USA. The hypothesis was that pellets of Al-Ga would oxidise in water, resulting in hydrogen evolution which could be directly used in a fuel cell to power a vehicle. This paper reports on new experiments on the reaction of a range of compositions of binary Al-Ga pellets in contact with water. It was found that the reaction does not go to completion, resulting in only a fraction of theoretical hydrogen evolution, and that – contrary to research findings of others – gallium is not a passive catalyst and is also partially oxidised in water. A new proposal on the reaction mechanism is presented. Even if theoretical H2 output was achieved, we show that the aluminium cycle is uneconomic and impractical, and that total CO2 emissions per km travelled are significantly higher than those from an equivalent petrol engine. Guidelines for improved alloy design and optimum microstructure for renewable hydrogen production from water are suggested.