Canada scientists split water into hydrogen using nanowires, diffuse sunlight, urea

University of Alberta (U of A) researchers have discovered a method to harness sunlight and specialized materials to cleanly and efficiently split water into hydrogen and oxygen. If scaled, this could prove to be a game-changer for providing portable, clean, and energy-dense fuel for the future.

Hydrogen promises to provide a clean and sustainable alternative to fossil fuels and could, it is hoped, become a major player in future energy mixes for many nations. However, at present, it is usually only made using solar panels to generate electricity, followed by electrolysis of water, which is very expensive and inefficient.

Led by Karthik Shankar, the U of A team’s method uses sunlight directly to split water, which wastes less energy and could be much cheaper. This is achieved, they explain, through novel use of urea (a common, cheap chemical often found in fertilizers and urine) and turning it into a material called carbon nitride using heat (this is called thermal condensation polymerization).

This carbon nitride, the team explains, readily absorbs sunlight. This gives its electrons extra energy and knocks them loose, leaving behind “holes” where electrons used to be.

Hydrogen from pee

In physics, we call these moving pieces electron-hole pairs — basically, tiny bundles of energy. Typically, these electrons and holes would quickly recombine and cancel each other out.

But when titanium dioxide (another cheap material) is added, it forms a junction with carbon nitride. This keeps the energized electrons and holes separated long enough to be useful.

In turn, thjese electrons react with protons (from water) and make hydrogen gas (H₂). The holes, on the other hand, react with hydroxyl ions (also from water) and make oxygen gas (O₂).

One of the main benefits of the U of A’s new method is that is can work on cloudy days as well as sunny days. This is achieved through the use of nanowires that can grab sunlight from many different angles.

The sytem doesn’t require big storage batteries, as the hydrogen gas produced itself stores the energy for transport.

The process is also theoretically more environmentally friendly as making silicon solar panels (the dominant tech today) is dirty and energy-intensive. Shankar’s process uses low-cost, abundant materials without extreme heating or lots of pollution.

Could be ready within three to five years

“You use a solar panel to generate electricity, and then use that electricity to do what’s called dry water splitting through electrolysis,” Shankar explained. “That involves a lot of energy loss, whereas using sunlight directly to generate hydrogen is far more efficient,” he added.

It could also open doors for improved energy independence as, right now, much of the world’s silicon comes from China and Russia. Shankar’s method could help other countries make clean energy with their own resources.

Moving forward, the team note that they are exploring the use of use melamine (another common material) instead of urea for the process. They also note that it could be modified to produce hydrogen from methanol too.

While not as clean as water, but still useful in certain situations. They hope this could be ready for big, commercial use in 3 to 5 years.

You can view the study for yourself in the Journal of the American Chemical Society.