The growing demand for energy, brought about by the rising standard of living in the developing world and global population growth, has made it imperative that new energy sources beyond fossil fuels be found to sustain and grow the current economy. The limited supply of fossil fuels and its adverse effect on the environment also makes it necessary that these sources should be abundant, renewable, secure, clean, safe, and cost-effective. In this regard hydrogen, the most abundant element in the universe and third most abundant element on the earth, has the potential to meet this growing energy need. In addition, hydrogen offers many advantages over other fuels: it is non-toxic, clean to use, and packs more energy per unit mass than any other fuel. However, hydrogen is not an energy source but an energy carrier. Since it does not occur freely in nature and is gaseous at room temperature and pressure, it needs to be produced and stored.
