“And this could dramatically lower the cost of hydrogen cars,” said Kaner, senior author of the study published in the journal Energy Storage Materials. The technology could be especially useful in rural areas, or to military units serving in remote locations.
“People need fuel to run their vehicles and electricity to run their devices. Now you can make both electricity and fuel with a single device,” Kaner said. It could also be part of a solution for large cities that need ways to store surplus electricity from their electrical grids, researchers said. “If you could convert electricity to hydrogen, you could store it indefinitely,” said Kaner.
Traditional hydrogen fuel cells and supercapacitors have two electrodes: one positive and one negative. The device has a third electrode that acts as both a supercapacitor, which stores energy, and as a device for splitting water into hydrogen and oxygen, a process called water electrolysis.
All three electrodes connect to a single solar cell that serves as the device’s power source, and the electrical energy harvested by the solar cell can be stored in one of two ways: electrochemically in the supercapacitor or chemically as hydrogen.
The device also is a step forward because it produces hydrogen fuel in an environmentally friendly way. Currently, about 95 per cent of hydrogen production worldwide comes from converting fossil fuels such as natural gas into hydrogen – a process that releases large quantities of carbon dioxide into the air, said Maher El-Kady, a UCLA postdoctoral researcher and a co-author of the research.
“Hydrogen energy is not ‘green’ unless it is produced from renewable sources,” El-Kady said. He added that using solar cells and abundantly available elements to split water into hydrogen and oxygen has enormous potential for reducing the cost of hydrogen production and that the approach could eventually replace the current method, which relies on fossil fuels.