Solar supercapacitor creates electricity and hydrogen fuel on the cheap

Hydrogen-powered vehicles are slowly hitting the streets, but although it's a clean and plentiful fuel source, a lack of infrastructure for mass producing, distributing and storing hydrogen is still a major roadblock. But new work out of the University of California, Los Angeles (UCLA) could help lower the barrier to entry for consumers, with a device that uses sunlight to produce both hydrogen and electricity.

The UCLA device is a hybrid unit that combines a supercapacitor with a hydrogen fuel cell, and runs the whole shebang on solar power. Along with the usual positive and negative electrodes, the device has a third electrode that can either store energy electrically or use it to split water into its constituent hydrogen and oxygen atoms – a process called water electrolysis.

To make the electrodes as efficient as possible, the team maximized the amount of surface area that comes into contact with water, right down to the nanoscale. That increases the amount of hydrogen the system can produce, as well as how much energy the supercapacitor can store.

"People need fuel to run their vehicles and electricity to run their devices," says Richard Kaner, senior author of the study. "Now you can make both fuel and electricity with a single device."

Hydrogen itself may be clean, but producing it on a commercial scale might not be. It's often created by converting natural gas, which not only results in a lot of carbon dioxide emissions but can be costly. Using renewable sources like solar can help solve both of those problems at once. And it helps that the UCLA device uses materials like nickel, iron and cobalt, which are much more abundant than the precious metals like platinum that are currently used to produce hydrogen.

"Hydrogen is a great fuel for vehicles: It is the cleanest fuel known, it's cheap and it puts no pollutants into the air – just water," says Kaner. "And this could dramatically lower the cost of hydrogen cars."

The new system could also help solve some of the infrastructure woes as well. Hydrogen vehicles can't really take off until consumers can easily find places to fill up, and while strides are being made in that department, with the UCLA device users can hook into the sun almost anywhere to produce their own fuel, which could be particularly handy for those living in rural or remote areas.

As an added bonus, the supercapacitor part of the system can chemically store the harvested solar energy as hydrogen. Doing so could help bolster energy storage for the grid. Although the current device is palm-sized, the researchers say that it should be relatively easy to scale up for those applications.

The research was published in the journal Energy Storage Materials.

Source: UCLA