New porous material can make renewable energy from water
Producing hydrogen from water using sunlight is a possible source of renewable energy in the future. Researchers at Linköping University have developed a material, so-called nanoporous cubic silicon carbide, which has promising properties for capturing solar energy and splitting water for such hydrogen production.
- We need to develop new sustainable energy systems to meet both the world’s energy needs and environmental problems, such as increasing carbon dioxide emissions and global warming, says Jianwu Sun, senior lecturer at the Department of Physics, Chemistry and Biology (IFM) at Linköping University, who has led the current study.
Hydrogen has three times the energy density of gasoline. With the help of a fuel cell, hydrogen can be used to generate electricity and today hydrogen-powered cars are available for purchase. When hydrogen is used to generate energy, nothing but pure water is formed. On the other hand, carbon dioxide emissions are created during the production of hydrogen, as the most common technology today uses fossil fuels to produce hydrogen gas. Production of one tonne of hydrogen in this way simultaneously produces 9-12 tonnes of carbon dioxide.
Renewable energy source without carbon dioxide emissions
Instead, producing hydrogen by dividing water molecules using solar energy is a sustainable alternative, which could provide hydrogen from renewable sources without causing carbon dioxide emissions. A major advantage would be that this approach makes it possible to convert solar energy into fuel that can be stored.
- Conventional solar cells can only generate energy during the day, and the energy must either be used directly, or saved in batteries, for example. Hydrogen is a promising source of energy that can be stored and transported in a similar way to traditional fuels such as gasoline and diesel, says Jianwu Sun.
Effectively dividing water into hydrogen using the energy in sunlight is not easy. To succeed, researchers need to find cost-effective materials that have the right properties to facilitate the reaction where water (H2O) can be decomposed into hydrogen (H2) and oxygen (O2) by photoelectrolysis. The energy required to split water comes mainly from the ultraviolet radiation and the visible light in the sunlight.
Therefore, the material must be able to absorb such radiation efficiently and use the captured energy to create charges that can be separated and have a sufficiently high energy to be able to split water molecules into hydrogen and oxygen. Most materials that have been studied so far are either not good enough to use the energy in visible sunlight (eg titanium dioxide, TiO2, which only absorbs ultraviolet radiation), or the material does not have the properties required to divide water into hydrogen (eg silicon , Si).
Porous material makes water splitting more efficient
Jianwu Sun’s research team has investigated whether the material cubic silicon carbide, 3C-SiC, could be used. They have now produced a form of cubic silicon carbide which has a variety of extremely small pores. The material, which they call nanoporous 3C-SiC, has promising properties for use in extracting hydrogen from water with sunlight. In the current study, published in the journal ACS Nano, the researchers show that the new porous material can effectively capture ultraviolet and a large part of the visible light. The porous structure favors the separation of charges with sufficiently high energy. In addition, the small pores provide a larger active surface that strengthens the charge transfer and increases the reaction surface, so that water splitting takes place even more efficiently.
“Above all, we show that nanoporous cubic silicon carbide strengthens the charge separation, which means that the cleavage of water into hydrogen is significantly better compared to flat silicon carbide,” says Jianwu Sun.
Article source: forskning.se
Member read also next article