The scientists behind the project have fused the optical properties of three dimensionalphotonic crystals (inverse opals of titanium dioxide, TiO2) and 2-3 nm gold nanoparticles to develop a highly active catalyst powder. The research paper has been published in Scientific Reports, the open-access journal of Nature.
This new photocatalyst produces more hydrogen than others developed so far by harnessing the properties of both photonic crystals and nanoparticles of a metal. According to Jordi Llorca, a researcher at the UPC's Institute of Energy Technology, the process involves "tuning" the two materials to amplify the effect. "You have to choose the right photonic crystal and the right nanoparticles", he adds.
In any photocatalyst made from gold nanoparticles and titanium dioxide crystals using ultraviolet light, which is only a small part of solar radiation (less than 3%), the process is the same: light excites the TiO2 electrons and promotes them to the conduction band, leaving holes on the other side. The electrons interact with the gold nanoparticles and are captured by them. According to the scientists, the novelty in this case is the use of a 3D photonic crystal that captures the visible part of the solar spectrum, precisely at the energy level at which the gold nanoparticles "resonate". As a result, it's possible to take advantage of the visible part of the solar spectrum rather than just the ultraviolet part. This translates into a significant boost in the performance of the process.
The new catalyst has great potential for application in industrial processes. According to researcher Jordi Llorca, making the move from the laboratory to an industrial plant would mean designing a reactor to operate outdoors in the sun, and using a solar collector to capture more sunlight.
A conventional plant for the production of hydrogen from natural gas generates about 300 tons of hydrogen a day. With the new catalyst developed at the UPC, researchers have managed to produce 0.025 litres of hydrogen in one hour using one gram of catalyst. Assuming eight hours of sunlight a day, the scientists estimate that an area measuring 10 x 10 km would be needed to produce hydrogen on an industrial scale.
A conventional plant for the production of hydrogen from natural gas generates about 300 tons of hydrogen a day. With the new catalyst developed at the UPC, researchers have managed to produce 0.025 litres of hydrogen in one hour using one gram of catalyst. Assuming eight hours of sunlight a day, the scientists estimate that an area measuring 10 x 10 km would be needed to produce hydrogen on an industrial scale.
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