From left, Jeffrey Long, Christopher Chang and Hemamala Karunadasa have discovered an inexpensive metal that can generate hydrogen from neutral water, even if it is dirty, and can operate in sea water. (Photo by Roy Kaltschmidt, Berkeley Lab Public Affairs)

A new catalyst may pave the way for cheaper and more efficient production of hydrogen gas from water. The cost of harvesting hydrogen is one of the major stumbling blocks keeping the gas from widespread use as an alternative fuel.

Discovered by researchers at Lawrence Berkeley National Laboratory and University of California at Berkeley, the catalyst uses a combination of oxygen, electricity and a metal called molybdenum to split a water molecule into its component parts, oxygen and hydrogen gas. With a very high melting point, molybdenum is typically used as a catalyst by single-cell organisms and is extremely effective in this combination.

Today, hydrogen gas is usually generated using a platinum catalyst about 70 times more expensive than Karunadasa’s new catalyst or by reacting water and natural gas at high temperatures, a process that still relies on fossil fuels.  In addition to being very expensive, the surface of the platinum catalyst gets coated by impurities in water becoming ineffective over time.

While this new molecule is certainly a big step in the right direction, Karunadasa and her colleagues noted that a significant amount of energy is still required to jump-start the chemical reaction.

“One problem is that we still have to apply a potential to generate water from hydrogen. That’s the one thing that is not cheap,” Karunadasa said. A potential is the base amount of energy required to initiate a reaction.  Karunadasa and her co-authors Christopher Chang and Jeffrey Long at Berkeley are now tweaking their catalyst to decrease the size of the initial energy input by changing the structure of the bond between the molybdenum atom and its surrounding atoms.

Another major break-through is that most catalysts require purified water or other chemicals, like organic solvents and acids, to harvest hydrogen from water, creating additional costs that can lead to large amounts of left over waste.  This catalyst works in plain water, dirty water and seawater.  “It’s already cheap to use water, but the fact that we can use seawater makes this extremely cheap,” said lead author Hemamala Karunadasa.

The researchers are also considering other metals similar to molybdenum that can accept large numbers of electrons in order to create other potential catalysts.  Hydrogen is a valued source of alternative energy because it burns so cleanly. Water vapor and energy are the only byproducts when hydrogen is used as fuel.  But the gas does not occur naturally, so a cheap, efficient method of producing the fuel is crucial to developing hydrogen as a viable alternative energy source.