Hydrogen production is attracting a lot of interest from the research and science community due to hydrogen’s properties as a clean energy source that can replace fossil fuels. There is also a push towards green hydrogen. Most hydrogen is produced from steam reforming, partial oxidation of methane, or coal gasification.
Green hydrogen, however, is made through the electrolysis of water – a process where an electric current splits water into hydrogen and oxygen. When using renewable energy for this method, it creates no emissions so it is considered the most environmentally friendly way of hydrogen production.
For decades, though, scientists have been trying to perform this process in a low cost and efficient way which is the big challenge and most attempts have failed. Splitting water into molecules is either more expensive than other methods or when tried to do cheaper it loses efficiency.
Sunlight For Hydrogen Production
Researchers from The University of Texas at Austin, however, may have found the answer to this puzzle. They use sunlight to efficiently split off oxygen molecules from water. This finding is groundbreaking and it is a step forward towards greater adoption of hydrogen as a key part of the future of energy.
The method of using sunlight to split the water is familiar to scientists since the 1970s, however, the reaction requires special materials that are equally efficient at staying stable during the reaction without degrading and absorbing light.
“It turns out materials that are good at absorbing sunlight tend to be unstable under the conditions required for the water-splitting reaction, while the materials that are stable tend to be poor absorbers of sunlight,” said Edward Yu, a professor in the Cockrell School’s Department of Electrical and Computer Engineering at the University of Texas.
Scientists have found that one material – silicon, efficiently absorbs sunlight, and combined it into a single device with another material – silicon dioxide that provides good stability.
However, a challenge appears – the electrons and holes created by the absorption of sunlight in silicon must be able to move easily across the silicon dioxide layer. That means the silicon dioxide layer should be no more than a few nanometers thick, which reduces its effectiveness in protecting the silicon absorber from degradation.
What Can Be Done?
Professor Yu and his team have used a technique that could solve this controversy. They coated the silicon dioxide layer with a thin film of aluminum and then heated the entire structure. As a result, arrays of nanoscale “spikes” of aluminum that completely bridge the silicon dioxide layer are formed. If they are replaced by nickel or other materials, it could help catalyze the water-splitting reactions.
When sunlight illuminates the device, it is capable of efficiently oxidizing water to form oxygen molecules while also generating hydrogen at a separate electrode and exhibit outstanding stability under extended operation. The technique employed to create these devices is already known in manufacturing semiconductor electronics, so it could be scaled for mass production.
The team will now aim to improve the efficiency of the oxygen forming from the water-splitting by increasing the reaction rate. The next major challenge is to completely split the water molecule to form hydrogen – the other part of the equation. That part is also deemed to be the easy one.
The evolution of green hydrogen production via electrolysis is getting traction as researchers around the world are working to improve the economics and efficiency of the process. With its ability to become one of the major energy sources in the future, hydrogen production from water is benefiting from research interest and thus increasing innovation.