Researchers from Stanford have found a way to split water into oxygen and hydrogen using very little energy; the hydrogen they obtain could be used to power fuel cells in zero-emissions vehicles.
I’m quite excited for cars that run on hydrogen, which are set to hit the market in 2015; but while they are always presented as “zero emission cars”, many of the hydrogen cars will actually use hydrogen obtained with natural gas – which is still a fossil fuel and still has considerable emissions. Hopefully, that will only be a temporary stage, and pretty soon, manufacturers will move on to greener, more sustainable solutions – like this project from Stanford University.
A team working there found a way to separate hydrogen from water cheaply and efficiently, producing water electrolysis only powered by a battery. The battery sends an electric current through two electrodes that split liquid water into hydrogen and oxygen gas. Unlike other water splitters that use precious-metal catalysts, the electrodes in the Stanford device are made of inexpensive and abundant nickel and iron.
“Using nickel and iron, which are cheap materials, we were able to make the electrocatalysts active enough to split water at room temperature with a single 1.5-volt battery,” said Hongjie Dai, a professor of chemistry at Stanford. “This is the first time anyone has used non-precious metal catalysts to split water at a voltage that low. It’s quite remarkable, because normally you need expensive metals, like platinum or iridium, to achieve that voltage.”
In addition to producing hydrogen, the same technique could be used to obtain chlorine gas and sodium hydroxide, an important industrial chemical.
Hydrogen cars and carbon emissions
The auto industry has considered developing hydrogen fuel cell as a promising alternative to the gasoline engine for decades, using fuel cell technology. Fuel cell technology is basically water splitting in reverse – it’s like creating water, and getting energy in the process. Basically, the fuel cell stores hydrogen which reacts with the oxygen from the air to create electricity which powers the car. The only by-product is water – no emissions whatsoever.
Earlier this year, Hyundai began leasing fuel cell vehicles in Southern California, but it’s still a local thing. In 2015, Toyota and Honda will hit the market, selling fuel cell cars. The only problem with this technology is a cheap way of obtaining hydrogen – something for which the Stanford team proposes a simple yet surprising solution.
“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.”
This could save time and a lot of money, potentially taking gas guzzling cars out of the streets in the long run. The discovery wouldn’t have been possible without Stanford graduate student Ming Gong, co-lead author of the study.
“Ming discovered a nickel-metal/nickel-oxide structure that turns out to be more active than pure nickel metal or pure nickel oxide alone,” Dai said. “This novel structure favors hydrogen electrocatalysis, but we still don’t fully understand the science behind it.”
Water electrolysis was, of course is not a new thing. The novely comes with the nickel/nickel-oxide catalyst, which significantly reduces the voltage necessary for electrolysis.
“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”
The next step in their research is to make the entire process fully sustainable – that is, obtain the energy for the batteries through solar panels – and there’s no reason why they shouldn’t be successful in their attempts.
“Hydrogen is an ideal fuel for powering vehicles, buildings and storing renewable energy on the grid,” said Dai. “We’re very glad that we were able to make a catalyst that’s very active and low cost. This shows that through nanoscale engineering of materials we can really make a difference in how we make fuels and consume energy.”
Journal Reference: Ming Gong,Wu Zhou,Mon-Che Tsai,Jigang Zhou,Mingyun Guan,Meng-Chang Lin,Bo Zhang,Yongfeng Hu,Di-Yan Wang,Jiang Yang,Stephen J. Pennycook,Bing-Joe Hwang& Hongjie Dai. Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis. Nature Communications 5, Article number: 4695 doi:10.1038/ncomms5695
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