EUGENE, Ore. -- With the help of a new method called "dual-electrode photoelectrochemistry," University of Oregon scientists have provided new insight into how solar water-splitting cells work. An important and overlooked parameter, they report, is the ion-permeability of electrocatalysts used in water-splitting devices.
Their discovery could help replace a trial-and-error approach to paring electrocatalysts with semiconductors with an efficient method for using sunlight to separate hydrogen and oxygen from water to generate renewable energy, says Shannon W. Boettcher, professor of chemistry and head of the Solar Materials and Electrochemistry Laboratory in the UO's Materials Science Institute.
The research is described in a paper placed online Dec. 1 in advance of regular publication in the journal Nature Materials.
Solar water-splitting cells, which mimic photosynthesis, require at least two different types of materials: a semiconductor that absorbs sunlight and generates excited electrons and an electrocatalyst, typically a very thin film of a metal oxide that contains elements such as nickel, iron and oxygen, which serves to accelerate the rate at which electrons move on and off water molecules that are getting split into hydrogen and oxygen.
"We developed a new way to study the flow of electrons at the interface between semiconductors and electrocatalysts," Boettcher said. "We fabricated devices which have separate metal contacts to the semiconductor and electrocatalyst."
To do so, lead author Fuding Lin, a postdoctoral researcher, electrically contacted a single-crystal of semiconducting titanium dioxide and coated it with various electrocatalyst films. A film of gold only 10 nanometers thick was used to electrically contact the top of the electrocatalysts. Both contacts were used as probes to independently monitor and control the voltage and current at semiconductor-electrocatalyst junctions with a de
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University of Oregon