The problem with emission-free hydrogen fuel is that the process of making it is definitely not emission-free.
Hydrogen-powered devices-–cars, mostly -run on hydrogen made from natural gas, a fossil fuel that produces greenhouse gas emissions.
That could be a major consideration for eco-conscious American consumers as more and more cars powered by hydrogen fuel cells come to market.
Not to worry, according to a team of scientists at Stanford University. The researchers have developed a low-cost, emission-free mechanism that uses a 1.5-volt battery to split water into its constituent elements of oxygen and hydrogen.
The team, led by Hongjie Dai, a Stanford professor of chemistry, uses an AAA "penlight" battery to split hydrogen from oxygen by running an electric current through two electrodes, a process called electrolysis. The electrodes are made of inexpensive iron and nickel, not costly catalysts made of precious metals.
"This is the first time anyone has used non-precious metal catalysts to split water at a voltage that low," Dai said. "It's quite remarkable." Dai's research team reported its findings in the Aug. 22 issue of the journal Nature Communications.
What's intriguing about hydrogen fuel cell technology is that it reverses the water-splitting process. To produce the electrical energy that powers the car, the cell gradually mixes its load of hydrogen gas with atmospheric oxygen. The only waste is water vapor, not the toxic gases of a combustion engine that relies on gasoline.
Vehicles powered by hydrogen fuel cells are already available for lease in Southern California, and more are on the way. Yet most won't operate as cleanly as advertised because they'll use fuel manufactured at plants that isolate hydrogen by combining steam and natural gas, which not only emits toxic carbon dioxide into the environment, but also uses up large amounts of energy.
Splitting water through electrolysis is a clean method of generating hydrogen, but it's expensive – or at least it was until Dai's team developed a method using inexpensive metals on its electrodes and demonstrated that the process can be expanded to an industrial scale.
"It's been a constant pursuit for decades to make low-cost electrocatalysts with high activity and long durability," Dai said. "When we found out that a nickel-based catalyst is as effective as platinum, it came as a complete surprise."
Besides being inexpensive, the use of nickel and nickel oxide greatly lowers the voltage needed to split water, which could save billions of dollars in electricity costs for hydrogen producers, according to Stanford graduate student Ming Gong, who discovered the new water-splitter method.
Gong, who co-authored the report, said his next chore is to improve the durability of the water-splitter. "The electrodes are fairly stable, but they do slowly decay over time," he said. "The current device would probably run for days, but weeks or months would be preferable. That goal is achievable based on my most recent results."