Researchers split water into hydrogen and oxygen using solar energy

Researchers at the Technion-Israel’s Institute of Technology have developed an innovative prototype system for the efficient and safe production of hydrogen using only solar energy. According to the Technion, this innovative system contains a two-layer solar cell, known as a Tandem cell, “which enables a more efficient use of the light spectrum.” This means that “a part of the Sun’s radiation is absorbed into the upper layer of the solar cell, which is made of semi-transparent iron oxide,” the Technion explained in a statement. “The radiation that is not absorbed in this layer passes through it and is subsequently absorbed by a photovoltaic cell, which is a specialized solar cell that converts the energy of light directly into electricity. “Together, the two layers of the system provide the energy needed to deconstruct the water,” it added.

The research was led by doctoral student Avigail Landman and masters student Rawan Halabi. The research was facilitated jointly by Prof. Avner Rothschild of the Technion’s Department of Materials Science and Engineering and Prof. Gideon Grader of the Faculty of Chemical Engineering. Dr. Paula Dias and Prof. Adelio Mendes of the University of Porto also contributed to the research.
Rothschild explained to The Jerusalem Post that being able to split water into hydrogen and oxygen using solar energy “provides a way to produce hydrogen fuel in a clean process that takes only water and solar energy and converts them to clean hydrogen fuel with no other byproducts, except for oxygen.

“The oxygen can be released to the atmosphere, there is absolutely no harm in this,” he said, adding that “it can also be used for chemical processes.”

Rothschild listed several ways in which the hydrogen produced by this process could replace fossil fuels like coal, oil, and natural gas. This could include heating residential and/or industrial areas; “fueling electric vehicles that run on hydrogen gas and produce water in the exhaust pipeline instead of toxic gases in oil or diesel engines; and producing ammonia that is necessary for fertilizers for food production,” among other uses.

Rothschild also stressed that the hydrogen produced can be used for power to gas conversion “for storing excess power produced during peak production times when power production is higher than the demand, by converting the excess power to hydrogen fuel via water splitting, storing the hydrogen and using it when and where the power is needed.”

This can be most useful for solar or wind farms that produce plenty of power during peak hours, “but produce nothing at night (solar farms) or when there is no wind (wind farms). “You cannot rely on these power sources to supply the demand, unless you can store excess energy produced during peak production hours and convert it back to power when needed,” he explained. “This is the major obstacle for increasing the use of solar farms and wind farms and making these renewable power sources our main source of electricity.” According to Rothschild, solar water splitting is also “an attractive way of storing solar energy in clean hydrogen fuel.”

He explained that this technology would give rise to an increased utilization of solar energy that can “replace conventional power stations such as coal or natural gas power stations, and would ultimately enable the transition from fossil fuel power production so solar power production.
“This would eliminate about a third of man-made CO2 emissions,” Rothschild added. However, he warned that one has to keep in mind that even when the technology becomes available, “the investment in building new infrastructure for replacing fossil fuels by hydrogen fuel would be enormous.“So it will take many years to get there,” he stressed.

Asked about how this new research changes the way hydrogen and oxygen is split, Rothschild said that it outlines a new path for solving one of the most critical challenges in water splitting, which is separating the hydrogen and oxygen gases. “In conventional water splitting the hydrogen and oxygen gases are produced [as] two electrodes [are] immersed in water in very close proximity to each other in order to minimize losses,” he explained. “You must separate the hydrogen produced on one of these electrodes from the oxygen produced on the other electrode. Otherwise they will recombine [to form water] or even worse – they could ignite fire spontaneously because the hydrogen and oxygen mixture is extremely flammable.”

To make sure they don’t remix, a membrane or diaphragm is then placed to separate the one electrode from the other. Rothschild stressed that these membrane or diaphragm separators are expensive, “and the cell assembly becomes very complicated because you need to make sure there are no leaks.” Moreover, in broad-field solar fields hydrogen is very difficult to produce in this configuration and that’s why this current breakthrough is so important.