Researchers have developed a new photoelectrode that could help to make the dream of producing cheap hydrogen fuel from sunlight and water into reality.
Although still at the experimental stage, the “revolutionary” device could be mass-produced inexpensively, say the researchers that developed it at the University of Exeter in the United Kingdom.
Like photosynthesis in plants, the new photoelectrode captures and stores solar energy in chemical bonds except that the bonds are in molecules of hydrogen and not plant sugars. Image: pixabay-1552088
They describe their pioneering work in in a paper that was recently published in the journal Scientific Reports.
Hydrogen is everywhere
Hydrogen is attracting renewed attention because it is a clean fuel; when you “burn” it in a fuel cell using oxygen from the air, it produces no carbon emissions.
However, although it is present in abundance on our planet, hydrogen is almost always married tightly to at least one other element. To make hydrogen fuel you have to separate it from its partner element(s).
The most common natural compound containing hydrogen is water (H2O), in which two hydrogens (H) are bound to one oxygen(O).
One of the barriers to achieving a hydrogen fuel economy is the prohibitive cost of separating hydrogen on a commercial scale.
There are currently several ways to produce hydrogen.
Photoelectrochemical water splitting
Photoelectrochemical (PEC), the technology behind the new photoelectrode, is very much at the development stage as a way to make hydrogen from water.
Using PEC water splitting to make hydrogen “has long been considered as the Holy Grail to a carbon-free hydrogen economy,” note the researchers.
PEC systems contain special semiconductors that allow them to use energy from the sun rather like plants harness solar energy using photosynthesis.
The first step of the process, which is called photoelectrolysis, occurs when the photoelectrode converts the sunlight that falls on it into electricity.
In the next step, the electricity splits water molecules into molecules of hydrogen and oxygen.
Solar fuel
The oxygen can be released harmlessly into the air and the hydrogen can be stored for later use.
The process is often referred to as a “solar fuel” technology because it locks solar energy in the hydrogen bonds.
A big attraction is that unlike solar panels, where you have to either use the electricity as soon as it is produced or store it in a battery, is that you get a storable fuel straight away.
PEC development is still in its infancy, and developers are looking for ways not only to bring down the cost but also to increase the efficiency so that the energy produced far exceeds the energy consumed to make it worth doing.
New photoelectrode is stable and cheap
A key challenge that the University of Exeter team believes it has overcome with its new photoelectrode is that it is stable and cheap and meets “the thermodynamic and kinetic criteria for photoelectrolysis.”
In their study paper, they describe how they made the photoelectrode out of “nanostructured” lanthanum iron oxide (LaFeO3) and then tested its ability to “spontaneously produce hydrogen from water using sunlight.”
They conclude that their results show that their “low cost” LaFeO3 photoelectrode is a “strong future candidate for renewable hydrogen generation.”
“Hydrogen is a promising alternative fuel source capable of replacing fossil fuels,” says the paper’s lead author Govinder Pawar, a postgraduate researcher at Exeter University’s Environment and Sustainability Institute, “as it has a higher energy density than fossil fuels (more than double), zero carbon emissions, and the only by-product is water.”
