A low-cost water splitter that runs on an ordinary AAA battery
August 22, 2014
A cheap, emissions-free device that uses a 1.5-volt AAA battery to split water into hydrogen and oxygen by electrolysis has been developed by scientists at Stanford University.
Unlike other water splitters that use precious-metal catalysts, the electrodes in the Stanford device are made of inexpensive, abundant nickel and iron.
“This is the first time anyone has used non-precious metal catalysts to split water at a voltage that low,” said Hongjie Dai, a professor of chemistry at Stanford. “It’s quite remarkable, because normally you need expensive metals, like platinum or iridium, to achieve that voltage.”
He and his colleagues describe the new device in a study published in the Aug. 22 issue of the journal Nature Communications.
The promise of hydrogen
Fuel cell technology is essentially water splitting in reverse. A fuel cell combines stored hydrogen gas with oxygen from the air to produce electricity, which powers the car.
The only byproduct is water — unlike gasoline combustion, which emits carbon dioxide, a greenhouse gas.
In 2015, American consumers will finally be able to purchase fuel cell cars from Toyota and other manufacturers. Although touted as zero-emissions vehicles, most of the cars will run on hydrogen made from natural gas, a fossil fuel that contributes to global warming.
Most of these vehicles will run on fuel manufactured at large industrial plants that produce hydrogen by combining very hot steam and natural gas, an energy-intensive process that releases carbon dioxide as a byproduct.
Splitting water to make hydrogen requires no fossil fuels* and emits no greenhouse gases. But scientists have yet to develop an affordable, active water splitter with catalysts capable of working at industrial scales.
Saving energy and money
The discovery was made by 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.”
The nickel/nickel-oxide catalyst significantly lowers the voltage required to split water, which could eventually save hydrogen producers billions of dollars in electricity costs, according to Gong. His next goal is to improve the durability of the device.
“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 researchers also plan to develop a water splitter than runs on electricity produced by solar energy.
“Hydrogen is an ideal fuel for powering vehicles, buildings and storing renewable energy on the grid,” said Dai. “This shows that through nanoscale engineering of materials we can really make a difference in how we make fuels and consume energy.”
“Another major use of the nickel oxide/nickel hydrogen evolution catalyst is the cathode for the chloroalkali industry [to produce chlorine and sodium hydroxide (caustic soda), which are commodity chemicals required by industry],” Dai told KurzweilAI in an email interview. “The improved activity by the catalyst might potentially save the electricity cost of the chloroalkali industry by 10–20 %, which is on the scale of billions of dollars, as the U.S. uses about 8–10% of its electrical energy on chloroalkali electrolysis.”
So when can we expect this innovation to be available commercially? “The catalysts can be produced at very large scale for industrial purposes,” he said. “Currently, the device could work for days, but we are still working on improving the stability of the catalysts. Once the stability is further improved to more than weeks, the device can be easily produced for commercialization, which may take several years.”
Other authors of the study include scientists at Oak Ridge National Laboratory, National Taiwan University of Science and Technology, and University of Tennessee. Principal funding was provided by the Global Climate and Energy Project (GCEP), the Precourt Institute for Energy at Stanford, and the U.S. Department of Energy.
Stanford Precourt Institute for Energy | Stanford University Professor Hongjie Dai has developed an emissions-free electrolytic device that splits water into hydrogen and oxygen at room temperature.
* Except for the relatively small amount of fuel used in providing a voltage source.
- Ming Gong et al., Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis, Nature Communications, 2014, DOI: 10.1038/ncomms5695