Hydrogen Production for Fuel Cells

Only small amounts of hydrogen occur naturally on Earth, yet the US Department of Energy estimates that the USA uses about 9 million tons per year, and, that this is set to grow if the "hydrogen economy" ever eventuates.

About 95% of the hydrogen in use is produced through steam reforming of natural gas, a catalytic process in which steam reacts with methane to yield carbon monoxide and hydrogen. This mixture is known as synthesis gas, or syngas, and is an intermediate in production processes for synthetic fuels, ammonia, methanol and other compounds.

Hydrogen is a high energy density fuel that is being considered as a cleaner source of future energy, particularly for low-temperature fuel-cell powered devices including vehicles. Fuel cells use electrochemical process to convert hydrogen and oxygen into water, producing current that powers a motor. Fuel cell vehicles require highly purified hydrogen such as is produced in the water-gas-shift reaction. This reaction strips residual carbon monoxide from the hydrogen generated through steam reforming of fossil fuels. Water-gas-shift catalysts decrease the amount of carbon monoxide in hydrogen and increase the hydrogen content by harvesting hydrogen from water molecules.

Currently, copper-based catalysts supported on zinc oxide and alumina are in use. Copper is pyrophoric, it can spontaneously ignite when exposed to air, so researchers have been looking for other more stable catalysts.

Platinum supported on cerium oxide is known to work, but platinum is expensive and cerium occurs in only a few places around the world. Scientists have discovered that sodium improves the platinum activity in the water-gas-shift reaction, which can now take place at low temperatures, even on inert materials such as silica. Less platinum is required, so the cost of hydrogen production should decrease.

Reference:
Yanping Zhai, Danny Pierre, Rui Si, Weiling Deng, Peter Ferrin, Anand U. Nilekar, Guowen Peng, Jeffrey A. Herron, David C. Bell, Howard Saltsburg, Manos Mavrikakis, and Maria Flytzani-Stephanopoulos. Alkali-Stabilized Pt-OHx Species Catalyze Low-Temperature Water-Gas Shift Reactions. Science, 24 September 2010: Vol. 329. no. 5999, pp. 1633 - 1636 DOI: 10.1126/science.1192449

Further Reading
Reaction Rates
Batteries and Fuel Cells

Study Questions

1. What are the 6 most abundant elements on Earth?
2. Natural Gas is the name given to a hydrocarbon. Give the IUPAC name and formula for this compound.
3. Write a balanced chemical reaction for the reaction between steam and natural gas to yield carbon monoxide and hydrogen.
4. Write equations to represent the electrochemical process to convert hydrogen and oxygen into water in a hydrogen fuel cell.
5. Cerium oxide is also known as ceria. Write a possible chemical formula for ceria.
6. Give the systematic name for alumina, and write its formula.
7. Give the systematic name for silica, and write its formula.