Water represents a very stable compound. Decomposing water takes extraordinary conditions such as temperatures in excess of 2,000 degrees Celsius (3,632 degrees Fahrenheit) or an energy exceeding 486 kilojoules. Even in this extreme environment, only 0.02 percent of the water decomposes.
Despite these challenges, the interest in water decomposition remains strong because the transformation generates hydrogen, a form of clean energy that may eventually fuel vehicles without creating pollution. The planet earth does not have natural reservoirs of hydrogen. It finds it existence only bonded to oxygen in water.
When submitted to high levels of stress, a molecule will break down into simpler chemical compounds. When water decomposes, two molecules of water break down into two molecules of hydrogen and one molecule of oxygen. This does not represent a chemical reaction but a destruction of the water molecules.
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Industrial hydrogen production achieves water decomposition by applying electricity to two electrodes placed in water. This process, called electrolysis, barely works with pure water, and the production centers must add an electrolyte, such as salt. Because pipelines cannot handle a heat of 2,000 degrees Celsius, producers place the electrolysis in a high-pressure environment, which allows them to lower the temperature to around 800 degrees Celsius. Conversion efficiency ranges between 50 and 75 percent, according to the National Renewable Energy Laboratory.