Making Hydrogen Fuel from Water and Visible Light Highly Efficient

By Allison Mills | Published

Yun Hang Hu and his doctoral student Bing Han have developed an efficient method to split water into hydrogen molecules using visible light.



“Hydrogen is the future of cars,” says Hu. “And if you want to power hydrogen cars, you have to make hydrogen fuels.”

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

Playbook of Black Titanium Dioxide, Methanol and Light






Playing in the Visible Light Spectrum


“It’s a two-part process,” Hu says, explaining that the catalyst is black titanium dioxide (with 1 percent platinum), which attaches to a silicon dioxide substrate in their set-up. Hu’s team first generated a “light-diffuse-reflected surface” for the silicon dioxide, making it bumpy, which traps light waves and bounces them around. “We put the catalyst on the scattered surface, and it can increase the light absorption by one hundred times,” he explains.

Light absorption is an important step that generates photo-excited electrons, but it’s only part of what’s needed. Using visible light shortens the playing field, altering the band gap to only 1.3 electron volts in black titanium oxide. Specifically, that’s because an electron is excited to conduction band from Ti3+ energy level instead of the valence band, which is like starting at the 10-yard line instead of the 50-yard line.

The photo-excited electron has less distance to travel to the conduction band, but methanol doesn’t like to play along. The shortened distance from methanol to Ti3+ energy level greatly reduces methanol’s oxidation reaction, giving it less motivation to fill the leftover hole in the Ti3+ energy level. So, it needed a little heat in the second step of the process to get that reaction going again.

“We used temperature to increase the energy for methanol oxidation to donate electrons,” Hu says, adding that in the experiment they found 280 degrees Celsius to be the sweet spot.


“The set-up is not complicated,” Hu says. “It’s actually convenient for scaling up commercially.”

