Making Hydrogen Fuel from Water

Monday, August 24, 2015 @ 05:08 PM gHale

One bottleneck of artificial photosynthesis is the efficiency of converting visible light into other energy is not efficient.

That may soon change.

There is now an efficient technique to produce hydrogen fuel, said researchers at Michigan Technological University.

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“Hydrogen is the future of cars,” said Yun Hang Hu, the Michigan Tech Charles and Carroll McArthur professor of Materials Science and Engineer, who developed the technique with his PhD student, Bing Han. “And if you want to power hydrogen cars, you have to make hydrogen fuels.”

In this new hydrogen production process, the key is to understand the interactions of a catalyst, light and a sacrificial molecule.

The method could make the sustainable production of hydrogen fuels more efficient.

The exchanges and counters between the materials used to split water look like a chemistry playbook. The players are black titanium dioxide (TiO2) and methanol (CH3OH) pitted against electron-hole recombination.

The goal is to produce hydrogen molecules. Basically, that occurs by moving an electron from one place to another. To achieve the goal, a water molecule captures an electron excited within a material.

When excited, electrons move up and down in different bands; the lower one is the valence band and the higher one is the conduction band. The valence band and the conduction band are like goal posts, and between them is the band gap, which is like the playing field. The excited electron is the ball passed around.

Solar energy, with both ultraviolet (UV) and visible light energy, gets the ball rolling. Light energy bounces off titanium dioxide, which is the material where the valence band and conduction band are in play. That excites an electron, making it a photo-excited charge that shoots up toward the conduction band. For UV light, the playing field is pretty big, and the band gap stretches 3.2 electron volts wide.

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