A fast ceramic mixed OH−/H+ ionic conductor for low temperature fuel cells
Peimiao Zou, Dinu Iuga, Sanliang Ling, Alex Brown, Shigang Chen, Mengfei Zhang, Yisong Han, A. Dominic Fortes, Christopher Howard, Shanwen Tao
Abstract
Abstract Low temperature ionic conducting materials such as OH − and H + ionic conductors are important electrolytes for electrochemical devices. Here we show the discovery of mixed OH − /H + conduction in ceramic materials. SrZr 0.8 Y 0.2 O 3- δ exhibits a high ionic conductivity of approximately 0.01 S cm −1 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 0.8 Y 0.2 O 3- δ . The OH − ionic conduction of CaZr 0.8 Y 0.2 O 3- δ in water was demonstrated by electrolysis of both H 2 18 O and D 2 O. The ionic conductivity of CaZr 0.8 Y 0.2 O 3- δ in 6 M KOH solution is around 0.1 S cm −1 at 90 °C, 100 times higher than that in pure water, indicating increased OH − ionic conductivity with a higher concentration of feed OH − ions. Density functional theory calculations suggest the diffusion of OH − 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.