Using energy from the sun, researchers converted seawater into hydrogen peroxide (H2O2) — a fuel that can be used in fuel cells, instead of elemental hydrogen.
The hydrogen economy — the idea of using hydrogen as an alternative fuel — was seen as very promising during the Bush administration, but its limitations quickly showed and progress put on hold.
For one, there’s an infrastructure problem in supplying cheap hydrogen. Most hydrogen today is made from reforming methane fuel using energy-intensive processes — energy which comes from fossil fuels. Secondly, hydrogen is very capricious. Being the smallest molecule, it readily leaches out of containers. For a hydrogen car equipped with fuel cells, this means that it needs to store the hydrogen in high-pressure tanks or, alternatively, in a liquid state under cryogenic temperatures. Again, this means a lot of energy.
The team led by Shunichi Fukuzumi at Osaka University provides an interesting solution to both problems. On one hand, the hydrogen peroxide fuel can be generated efficiently from seawater (H2O), “the most earth-abundant resource”, solely using energy from the sun. On the other hand, the fuel can be stored in ambient conditions at high densities.
To generate the hydrogen peroxide, a photoelectrochemical cell is bathed in sunlight. The photons are absorbed by a photocatalyst which becomes activated and triggers the oxidation and reduction of oxygen from the seawater. A full 24-hours later, the hydrogen peroxide concentration in the seawater reaches 48 mM, or 24 times more than that reported with previous methods.
“In the future, we plan to work on developing a method for the low-cost, large-scale production of H2O2 from seawater,” Fukuzumi said for Phys.org. “This may replace the current high-cost production of H2O2 from H2 (from mainly natural gas) and O2.”
Responsible for this massive boost in efficiency, which measures 0.55 percent, seems to be the chlorine naturally found in seawater. Overall, the system is still lacking. Right now, making H2O2 using conventional methods and energy from solar panels is a lot more efficient, but there’s room to grow. One day, this process might be refined so the fuel is produced cheaply, efficiently and fast. Oh, and another thing. Hydrogen peroxide is one the most reactive chemicals out there and will explode if heated to boiling. If a hydrogen peroxide tank is ever fitted to a car, engineers should better make it damn safe.
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