Efficiently enhance the proton conductivity of YSZ-based electrolyte for low temperature solid oxide fuel cell

Yttrium stabilized zirconia (YSZ) as a typical oxygen ionic conductor has been widely used as the electrolyte for solid oxide fuel cell (SOFC) at the temperature higher than 1000 degrees C, but its poor ionic conductivity at lower temperature (500-800 degrees C) limits SOFC commercialization. Compared with oxide ionic transport, protons con-duction are more transportable at low temperatures due to lower activation energy, which delivered enormous potential in the low-temperature SOFC application. In order to increase the proton conductivity of YSZ-based electrolyte, we introduced semiconductor ZnO into YSZ electrolyte layer to construct heterointerface between semiconductor and ionic conductor. Study results revealed that the heterointerface between ZnO and YSZ pro-vided a large number of oxygen vacancies. When the mass ratio of YSZ to ZnO was 5:5, the fuel cell achieved the best performance. The maximum power density (Pmax) of this fuel cell achieved 721 mW cm-2 at 550 degrees C, whereas the Pmax of the fuel cell with pure YSZ electrolyte was only 290 mW cm-2. Further investigation revealed that this composite electrolyte possessed poor O2-conductivity but good proton conductivity of 0.047 S cm-1 at 550 degrees C. The ionic conduction activation energy of 5YSZ-5ZnO composite in fuel cell atmosphere was only 0.62 eV. This work provides an alternative way to improve the ionic conductivity of YSZ-based electrolytes at low operating temperatures.