Just as a good meal requires appropriate, well-prepared ingredients, developing better green fuel alternatives necessitates the combination of the right materials and methods.
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Image Credit: Xi’an Jiaotong-Liverpool University
A group of experts from China and the United Kingdom has discovered new techniques to refine the recipe for the manufacturing of solar fuels.
Hydrogen is a zero-emission energy source that can be generated from water using solar energy and has enormous promise for assisting in the mitigation of the climate crisis.
The method of producing hydrogen from water is named “water splitting” since it breaks water into its two elements, hydrogen and oxygen. A semiconductor photocatalyst, a substance or compound that absorbs sunlight and then utilizes its energy to split water, is required.
However, the efficacy of semiconductor photocatalysts for water splitting varies.
The researchers discovered strategies to boost hydrogen production efficiency by combining unique technologies and materials to develop new types of photocatalysts.
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 suitable energy there is for water splitting, and so hydrogen production is increased.
Dr. Graham Dawson, Study Lead, Xi’an Jiaotong-Liverpool University
Finding the Perfect Recipe
According to Yanan Zhao, the first author of one of the team’s latest investigations, modifying the materials usually used as photocatalysts helps to overcome their limits. Titanium dioxide is one of the most commonly utilized materials.
Titanium dioxide can harness energy directly from the sun with negligible pollution and shows great potential in the development of solar-related technologies. However, it can only be activated by UV light, which accounts for only 7% of sunlight. It cannot absorb the energy of visible light.
Yanan Zhao Study First Author, Xi’an Jiaotong-Liverpool University
Zhao received her master’s degree in chemistry from XJTLU and was awarded a full scholarship to pursue her Ph.D. at the University of North Dakota.
The scientists found that combining boron nitride with a type of titanium dioxide developed a photocatalyst that can absorb energy from wavelengths other than UV light. Boron nitride, a boron-nitrogen combination, has high electrical conductivity and can tolerate temperatures up to 2000 ºC.
To prepare the composite photocatalytic material, we combined boron nitride with titanate nanotubes, which are tube-like structures with dimensions measured in nanometres – one nanometre 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 produced a very stable composite photocatalyst. It can absorb light from a wider range of wavelengths and produce more hydrogen compared to traditional physical mixing methods.
Yanan Zhao Study First Author, Xi’an Jiaotong-Liverpool University
A Gold Rush
Dr. Dawson’s team discovered an additional approach for enhancing photocatalytic effectiveness in water splitting in a second investigation.
They discovered that coating the surfaces of some types of photocatalytic devices with gold nanoparticles of a specified size boosted the amount of light they could absorb.
“The structure of the photocatalytic material used is very important. In this study, we used two forms of photocatalytic nanostructures—nanosheets and nanotubes. We coated them with differently sized gold particles to see which combination produced the highest amount of hydrogen from water,” Shiqi Zhao, this study’s first author.
“Our results showed that the nanosheets modified with small, uniform gold particles had the best photocatalytic performance out of the materials we tested. These gold-coated nanostructures showed approximately 36 times more photocatalytic hydrogen production performance than unmodified nanotubes,” he notes.
Shiqi Zhao concludes, “This provides a new understanding of how semiconductor photocatalytic materials can be modified with gold nanoparticles and has valuable applications in the fields of photocatalytic hydrogen production, solar cells, and optical sensors.”
Journal References:
- Zhao, Y., et al. (2023). Enhanced photocatalytic hydrogen production by the formation of TiNT-BN bonds. Applied Surface Science. doi.org/10.1016/j.apsusc.2023.157005.
- Zhao, S., et al. (2023). Enhanced photocatalytic activity through anchoring and size effects of Au nanoparticles on niobate nanotubes and nanosheets for water splitting. Optical Materials. doi.org/10.1016/j.optmat.2023.113753.