Stanford researchers have developed an inexpensive device that uses light to split water into oxygen and clean-burning hydrogen. It will be useful to supplement solar cells with hydrogen-powered fuel cells that can generate electricity when the sun isn’t shining or demand is high.
The silicon semiconductor coated in an ultrathin layer of nickel could help pave the way for large-scale production of clean hydrogen fuel from sunlight.
To produce clean hydrogen for fuel cells, scientists have turned to an emerging technology called water splitting. Two semiconducting electrodes are connected and placed in water. The electrodes absorb light and use the energy to split the water into its basic components, oxygen and hydrogen. The oxygen is released into the atmosphere, and the hydrogen is stored as fuel.
When energy is needed, the process is reversed. The stored hydrogen and atmospheric oxygen are combined in a fuel cell to generate electricity and pure water.
The entire process is sustainable and emits no greenhouse gases. But finding a cheap way to split water has been a major challenge.
The Standford team applied a 2-nanometer-thick layer of nickel onto a silicon electrode, paired it with another electrode and placed both in a solution of water and potassium borate. When light and electricity were applied, the electrodes began splitting the water into oxygen and hydrogen, a process that continued for about 24 hours with no sign of corrosion.
To improve performance, the researchers mixed lithium into the water-based solution. Remarkably, adding lithium imparted superior stability to the electrodes. They generated hydrogen and oxygen continuously for 80 hours – more than three days – with no sign of surface corrosion.