Closer to the perfect recipe to produce solar fuels

2023-06-12 16:36:43

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MADRID, 12 Jun. (EUROPA PRESS) –

A team of researchers from China and the UK found new ways to optimize the mix of materials and methods for the production of solar fuels.

Their findings have been published in two articles, one in the journal Applied Surface Science and the other in Optical Materials.

Hydrogen is a zero-emission energy source that can be produced from water using solar energy and offers great potential to help mitigate the climate crisis. The process of producing hydrogen from water is called “water division” because it decomposes water into its two elements, hydrogen and oxygen. The splitting of water requires a semiconductor photocatalyst, a substance or compound that it absorbs sunlight and then uses its energy for the splitting process.

However, semiconductor photocatalysts for water splitting vary in their efficiency. By using novel combinations of methods and materials to create new types of photocatalysts, researchers have improved the efficiency of hydrogen production.

Dr Graham Dawson, who led the studies at Xi’an Jiaotong University-Liverpool, explains it’s a statement: “By adding materials such as gold or boron nitrate to our photocatalysts using particular mixing methods, we can increase the amount of light that is absorbed.

“The more light that is absorbed, the more adequate energy there is for water splitting, and therefore increases hydrogen production“, dice.

Modifying materials commonly used as photocatalysts helps overcome their limitations, says Yanan Zhao, first author of the Applied Surface Science paper. One of the most widely used materials is titanium dioxide. “Titanium dioxide can harness energy directly from the sun with negligible pollution and shows great potential in the development of technologies related to solar energy“, dice.

“However, it can only be activated by ultraviolet light, which represents only 7% of sunlight. Cannot absorb energy from visible light“, explains Zhao, who received his master’s degree in chemistry from XJTLU and obtained a doctoral fellowship at the University of North Dakota.

The researchers found that adding boron nitride to a form of titanium dioxide produced a photocatalyst that can absorb energy of more wavelengths than ultraviolet light. Boron nitride, a compound of boron and nitrogen, has good electrical conductivity and can withstand temperatures up to 2,000°C.

Zhao explains the process: “To prepare the composite photocatalytic material, we combine boron nitride with titanate nanotubes, which are tube-like structures with dimensions measured in nanometers: A nanometer is one billionth of a meter.

“By optimizing the ratio of boron nitride to titanate nanotubes and using chemical processes to combine the compounds, we produce a very stable composite photocatalyst. It can absorb light of a broader range of wavelengths and produce more hydrogen compared to conventional methods.” traditional physical mixing.

In the second study, published in Optical Materials, Dr. Dawson’s team found an additional option to improve photocatalytic efficiency in water splitting. They coated the surfaces of specific types of photocatalytic structures with a specific size of gold nanoparticles, thus increasing the amount of light they could absorb.

Shiqi Zhao, the first author of this study, explains: “The structure of the photocatalytic material used is very important. In this study, we used two forms of photocatalytic nanostructures: nanosheets and nanotubes. We covered them with gold particles of different sizes to see which combination produced the most hydrogen from the water.

“Our results showed that nanosheets modified with small, uniform gold particles had the best photocatalytic performance of the materials we tested. These gold-coated nanostructures showed approximately 36 times higher photocatalytic hydrogen production performance than unmodified nanotubes,” he continues. .

“This provides a new understanding of how semiconductor photocatalytic materials can be modified with gold nanoparticles and It has valuable applications in the fields of photocatalytic hydrogen production, solar cells, and optical sensors.”