New recipes for better solar fuel production

Recently, a team of researchers from China and the United Kingdom found new ways to improve the recipe for making solar fuel.

Hydrogen is an emission-free energy resource that can be extracted from water using solar energy and offers great potential to reduce the climate crisis.

The process of making hydrogen from water is called “water separation” because it breaks water into two elements, hydrogen and oxygen. Splitting water requires a semiconductor photocatalyst, which is a material or compound that absorbs sunlight and then uses its energy in the splitting process.

However, semiconductor photocatalysts for water splitting have different efficiencies.

By using new combinations of methods and materials to create new photocatalysts, the researchers have improved the efficiency of hydrogen production.

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

“The more light that is absorbed, the more energy is available to split the water, so that more hydrogen is produced,” he explains.

Find the perfect recipe

Yan’an Gao, first author of one of the team’s recent studies, explains that modifying materials commonly used as photocatalysts helps overcome their limitations. Titanium dioxide is one of the most widely used materials.

“Titanium dioxide can harness energy directly from the sun with little pollution and has great potential for developing solar energy technologies,” she says.

explains Zhao, who received a master’s degree in chemistry from XJTLU and a full scholarship for her Ph.D. from the University of North Dakota.

The researchers found that adding boron nitride to a form of titanium dioxide creates a photocatalyst that can absorb the energy of more wavelengths than ultraviolet light. Boron nitride, a compound of boron and nitrogen, has good electrical conductivity and can withstand temperatures of up to 2000 degrees Celsius.

Zhao explains the process: “To produce the photonic composite material, we combined boron nitride with titanium nanotubes, which are tubular structures with dimensions in nanometers — one nanometer is one-billionth of a meter.

“By optimizing the ratio of boron nitride to titanium nanotubes and using chemical methods to combine the compounds, we have produced a highly stable composite photocatalyst. It can absorb light from a wider wavelength range and generate more hydrogen than conventional physical mixing methods.”

gold rush

In a second study, the team led by Dr. Dawson identified another way to improve the efficiency of photocatalysis in water splitting.

They found that coating the surfaces of certain types of photocatalytic structures with a certain size of gold nanoparticles increased the amount of light they could absorb.

“The structure of the photocatalytic material used is very important,” says Shiqi Gao, first author of this study. In this study, we used two forms of photocatalytic nanostructures – nanosheets and nanotubes.

“We coated them with different sized gold particles to see which combination produced the most hydrogen from the water.

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

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