Hydrogen is the most abundant element in the universe, so far as anyone knows. When it is used as a fuel, it has no emissions other than water vapor and heat. If it is so clean burning and there’s so much of it, why not just replace all fossil fuels with hydrogen fuel and solve the earth’s tendency to overheat in one fell swoop? Or swell foop, if you prefer.
The idea is enticing, but the devil is in the details, they say. Chemically, hydrogen is one of the most reactive elements in the periodic table, which means it loves to combine with other elements. Slap it together with two oxygen atoms and you get water. Mix it in with carbon atoms and you get oil. From oil you get gasoline, diesel fuel, and about a bazillion different plastics.
Free hydrogen does not exist in nature, and separating it from oxygen or carbon takes a tremendous amount of energy. That hasn’t stopped Japan from making a huge bet on hydrogen fuel. The Olympics will descend on Tokyo in 2020 and the island nation has vision of powering the whole spectacle with hydrogen.
Advocates like to point out the zero-emissions benefits of hydrogen fuel. Detractors — like some guy in California named Elon Musk — respond that it makes more sense to take the energy needed to free hydrogen and use it to power electric vehicles directly. But what if there were a way to make pure hydrogen using far less energy? That would be pretty cool, wouldn’t it? Scientists around the world are researching how to do exactly that.
→ Related: Hydrogen Fuel Cell Cars — #FAIL, In Depth
Nonocavities & Nanoflakes
At the University of South Florida, Professor Yang Yang and his team of researchers say they have developed a new nanomaterial that can extract hydrogen from sea water using sunlight. The key is a new photocatalyst — a material that spurs a chemical reaction using energy from light. Previously, such catalysts could only work with pure water, which takes lots of energy to make in the first place. “We’ve opened a new window to splitting real water, not just purified water in a lab,” Yang said. “This really works well in seawater.”
In the new catalyst, tiny nanocavities were etched onto the surface of an ultrathin film of titanium dioxide. Those nano-cavities are then coated with nanoflakes of molybdenum disulfide only one atom thick. Most catalysts can only use a portion of the visible light spectrum. The new material is able to use almost all of it — from ultraviolet to near infrared — by varying the amount of sulfur deposited on those nanoflakes.
“We can absorb much more solar energy from the light than the conventional material,” Yang says. “Eventually, if it is commercialized, it would be good for Florida’s economy. We have a lot of seawater around Florida and a lot of really good sunshine.” Yang is one of those people who believes hydrogen is the fuel of the future. Producing a chemical fuel using solar power is preferable to making electricity from solar panels because electricity must either be used or stored in batteries which eventually degrade. On the other hand, hydrogen gas is easily stored and transported.
Yang says his catalyst is inexpensive and easy to manufacture. Now that he can make hydrogen from seawater, his next mission is to develop a catalyst that can separate hydrogen from wastewater.
Replacing Metals With Phosphorous
Meanwhile, researchers at Osaka University in Japan say they also have created a new catalyst for making hydrogen from water that also uses a larger portion of the visible light spectrum. It does away with the need for expensive metals like platinum used in traditional catalysts and replaces them with black phosphorous, which is readily available and quite inexpensive.
“We were pleased to find a good amount of hydrogen produced from water using our new composite photocatalyst with graphitic carbon nitride and black phosphorus,” says Professor Tetsuro Majima. “But what we didn’t expect to find was that even when using low-energy light, in the near infrared, the photocatalyst continued to produce hydrogen.”
“The hydrogen economy faces a great many challenges, but our work demonstrates the potential for efficiently and cheaply producing hydrogen from water with a photocatalyst based on widely abundant elements. This is an important step toward making other hydrogen-based technologies economically and environmentally viable,” Majima says.
So there you have it. New catalysts from two different teams of researchers located on opposite sides of the planet that promise cheap, abundant hydrogen gas to power a shiny new, zero-emissions hydrogen economy.
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