A fast ceramic mixed OH<sup>-</sup>/H<sup>+</sup> ionic conductor for low temperature fuel cells.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38291342.
- Also identified by DOI 10.1038/s41467-024-45060-1 and PMC identifier 10827789.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Low temperature ionic conducting materials such as OH<sup>-</sup> and H<sup>+</sup> ionic conductors are important electrolytes for electrochemical devices. Here we show the discovery of mixed OH<sup>-</sup>/H<sup>+</sup> conduction in ceramic materials. SrZr<sub>0.8</sub>Y<sub>0.2</sub>O<sub>3-δ</sub> exhibits a high ionic conductivity of approximately 0.01 S cm<sup>-1</sup> at 90 °C in both water and wet air, which has been demonstrated by direct ammonia fuel cells. Neutron diffraction confirms the presence of OD bonds in the lattice of deuterated SrZr<sub>0.8</sub>Y<sub>0.2</sub>O<sub>3-δ</sub>. The OH<sup>-</sup> ionic conduction of CaZr<sub>0.8</sub>Y<sub>0.2</sub>O<sub>3-δ</sub> in water was demonstrated by electrolysis of both H<sub>2</sub><sup>18</sup>O and D<sub>2</sub>O. The ionic conductivity of CaZr<sub>0.8</sub>Y<sub>0.2</sub>O<sub>3-δ</sub> in 6 M KOH solution is around 0.1 S cm<sup>-1</sup> at 90 °C, 100 times higher than that in pure water, indicating increased OH<sup>-</sup> ionic conductivity with a higher concentration of feed OH<sup>-</sup> ions. Density functional theory calculations suggest the diffusion of OH<sup>-</sup> ions relies on oxygen vacancies and temporarily formed hydrogen bonds. This opens a window to discovering new ceramic ionic conducting materials for near ambient temperature fuel cells, electrolysers and other electrochemical devices.