Researchers at Michigan Technological University (MTU) have found an efficient technique to produce hydrogen fuel from water and visible light.
Mimicking photosynthesis is a difficult process. Visible light is the bottleneck of artificial photosynthesis since converting it into another form of energy is very inefficient.
The new technique was developed by Yun Hang Hu, Charles and Caroll McArthur Professor of Materials Science, and Bing Han, his Ph.D student at Michigan Tech.
“Hydrogen is the future of cars. And if you want to power hydrogen cars, you have to make hydrogen fuels,” said Hu. “With the new process, the key factor is to understand catalyst interactions, light and sacrificial molecules.”
The research team used black titanium dioxide (TiO2) and methanol (CH3OH) compounds and pitted them against electron-hole recombination. The objective of the experiment was to produce hydrogen molecules by moving electrons from one place to another. This was achieved using solar energy, both ultraviolet (UV) and visible light.
Visible light was central to the experiment since it constitutes 45% of solar energy. Hu’s team increased the yield and energy efficiency by two magnitudes than previous experiments.
Black Titanium Dioxide (1% platinum) acts as a catalyst, which attaches itself to a silicon dioxide substrate. Hu’s team produced a light-diffuse-reflected surface for silicon dioxide to make it bumpy, so that it could trap light waves and bounce them around.
The reactions between titanium dioxide, methanol and UV produced the hydrogen molecules. “It’s a two-part process. We put the catalyst on the scattered surface, and it can increase the light absorption by one hundred times,” explained Hu.
With heat and modified silicon dioxide substrate, Hu’s team designed a different set-up for the experiment. Water in the form of steam was pushed into a chamber where it collided with a roughened silicon dioxide disk studded with black titanium dioxide-platinum catalyst. Visible light excited the electrons, allowing hydrogen to be siphoned off.
The new method is a hybrid process which uses both heat and light, and has opened new pathways for visible light photosynthesis. The method is also one step closer to actually mimicking photosynthesis and making sustainable production of hydrogen fuel far more efficient.
Image Courtesy www.mtu.edu