New method can generate electricity from seawater

Scientists have used sunlight to efficiently turn seawater into hydrogen peroxide, which can then be used in fuel cells to generate electricity.
It is the first photocatalytic method of hydrogen peroxide (H2O2) production that achieves a high enough efficiency so that the H2O2 can be used in a fuel cell, researchers said.
"The most earth-abundant resource, seawater, is utilised to produce a solar fuel that is H2O2," said Shunichi Fukuzumi from Osaka University in Japan, who led the research.
Researchers developed a new photoelectrochemical cell, which is basically a solar cell that produces H2O2.
When sunlight illuminates the photocatalyst, it absorbs photons and uses the energy to initiate chemical reactions - seawater oxidation and the reduction of O2 - in a way that ultimately produces H2O2.

After illuminating the cell for 24 hours, the concentration of H2O2 in the seawater reached about 48 Millimolar (mM), which greatly exceeds previous reported values of about 2 mM in pure water, 'Phys.Org' reported.

Researchers found that the negatively charged chlorine in seawater is mainly responsible for enhancing the photocatalytic activity and yielding the higher concentration.
Overall, the system has a total solar-to-electricity efficiency of 0.28 per cent.
Although the total efficiency compares favourably to that of some other solar-to-electricity sources, such as switchgrass (0.2 per cent), it is still much lower than the efficiency of conventional solar cells.
The researchers expect that the efficiency can be improved in the future by using better materials in the photoelectrochemical cell, and they also plan to find methods to reduce the cost of production.

The research was published in the journal Nature Communications.