Researchers at Osaka University found a way to turn seawater—one of the most abundant resources on Earth—into hydrogen peroxide (H2O2) using sunlight, which can then be used to generate electricity in fuel cells. This adds to the ever growing number of existing alternative energy options as the world continues to move towards green energy.
“Utilization of solar energy as a primary energy source has been strongly demanded to reduce emissions of harmful and/or greenhouse gases produced by burning fossil fuels. However, large fluctuation of solar energy depending on the length of the daytime is a serious problem. To utilize solar energy in the night time, solar energy should be stored in the form of chemical energy and used as a fuel to produce electricity,” the researchers wrote in their paper.
As previously mentioned, the new research, instead of harvesting hydrogen from pure water, turns seawater into hydrogen peroxide. Gaseous hydrogen production from pure water has a lower solar energy conversion and is much harder to store, whereas the team notes, “H2O2 can be produced as an aqueous solution from water and O2 in the air.”
It is also much easier and safer to store and transport in higher densities, compared to highly compressed hydrogen gas.
There are other methods of producing H2O2, but they are impractical in that the processes themselves require a lot of energy, essentially defeating the purpose. This is the first time someone developed a photocatalytic method efficient enough to make H2O2 use in fuel cells viable.
The process involves a new photoelectrochemical cell developed to produce H2O2 when sunlight illuminates the photocatalyst, which then absorbs photons and initiates chemical reactions with the energy, resulting in H2O2.
A test conducted for 24 hours shows that the H2O2 concentration in seawater reached about 48mM (millimolar), compared to 2mM in pure water. Researchers found that this was made possible by seawater’s negatively charged chlorine enhancing the photocatalysis.
That said, this method isn’t yet as good as other solar power processes, but it’s a start. Researchers aim to improve efficiency with better materials and lower costs.
“In the future, we plan to work on developing a method for the low-cost, large-scale production of H2O2 from seawater,” Fukuzumi said. “This may replace the current high-cost production of H2O2 from H2 (from mainly natural gas) and O2.”