Scientists observe water molecules flipping before they separate, pointing out how to produce more affordable hydrogen fuel
Scientists have observed water molecules splitting in real time to form hydrogen and oxygen. Just before they split, the molecules did something entirely unexpected: They flipped 180 degrees.
This micro acrobatic stunt requires energy, which explains why splitting water demands more energy than theoretical calculations indicated.
The researchers suggest that further study could provide vital insights into enhancing the efficiency of splitting water molecules—paving the way for more affordable, clean hydrogen fuel.
Hydrogen possesses several key properties that render it an attractive source of green energy. This energy-rich fuel can power trucks and even cargo ships, and it stands as the sole alternative to fossil fuels in industries such as steel and fertiliser manufacturing. When burned, the fuel emits water instead of carbon dioxide.
However, the steep energy requirements for hydrogen production significantly limit the scale at which the fuel can be produced. According to the International Energy Authority, 322 million tonnes of hydrogen fuel must be generated annually to satisfy global energy needs. Yet, in 2023, only 97 million tonnes were produced at a monetary cost 1.5 to six times higher than fossil fuel production—and the vast majority of it was also made using fossil fuels.
Hydrogen fuel is produced by adding water to an electrode and then splitting the water with an applied voltage into hydrogen and oxygen. This process is most efficient when the chemical element iridium is used as a catalyst for the oxygen evolution reaction, which cleaves oxygen from water molecules. However, iridium only arrives on our planet through meteorite impacts, making it expensive and rare.
However, even when using iridium, the process is less efficient than scientists believe it ought to be. “It ultimately consumes more energy than what is theoretically calculated. If you do the sums, it should require 1.23 volts. However, in practice, it needs closer to 1.5 or 1.6 volts,” noted study lead author Franz Geiger, a professor of chemistry at Northwestern University. “Covering that extra voltage incurs a cost, and that’s why water splitting hasn’t been done on a large scale.”
To better understand the energy requirements of this process and why it is less efficient than theory suggests, the researchers placed water on an electrode inside a container and measured the positions of the molecules using the amplitude and phase of laser light directed at them.
When the scientists applied a voltage across the electrode, they observed that the molecules flipped and rotated rapidly so that their two hydrogen atoms in contact with the electrode faced upwards while the oxygen atom faced downwards.