Cool Fuel Cells
A new electrolyte works at room temperature.
Source: “Colossal Ionic Conductivity at Interfaces of Epitaxial ZrO2:Y2O3/SrTiO3 Heterostructures”
Jacobo Santamaria et al.
Science 321: 676-680
Results: A new electrolyte developed for use in solid-oxide fuel cells has 100 million times the ionic conductivity of conventional electrolytes at room temperature.
Why it matters: Solid-oxide fuel cells show promise for power generation because they convert a wide variety of fuels–including gasoline, hydrogen, and natural gas–into electricity more efficiently than conventional generators do. But they have been very expensive, and limited in their applications, because they require electrolytes that function only at temperatures above 600 °C. The new electrolyte works at temperatures hundreds of degrees cooler.
Methods: A solid-oxide fuel cell consists of two electrodes separated by an electrolyte. Fuel is fed to one electrode and oxygen to the other. The electrolyte transfers oxygen ions from one electrode to the other, where they combine with the fuel in a chemical reaction that releases electrons, producing an electric current. Conventional electrolytes require high temperatures because they don’t conduct ions well at room temperature.
To make the new material, the researchers combined nanometer-thick layers of the electrolyte, an yttria-stabilized zirconia, with 10-nanometer-thick layers of strontium titanate. The difference between the crystal structures of these two materials leads to gaps in the electrolyte that allow oxygen ions to move freely at relatively low temperatures.
Next steps: Ionic conductivity is difficult to measure in extremely thin films like the one tested, so the improvement requires verification. What’s more, creating low-temperature fuel cells will also require new electrodes that operate at low temperatures.