The environmental benefits of fuel cells and electrolyzers have become increasingly recognized in recent years. Fuel cells and electrolyzers that can operate at intermediate temperatures (300–450 °C) require, in principle, neither the precious metal catalysts that are typically used in polymer-electrolyte-membrane systems nor the costly heat-resistant alloys used in balance-of-plant components of high-temperature solid oxide electrochemical cells. These devices require an electrolyte with high ionic conductivity, typically more than 0.01 S cm−1, and high chemical stability. To date, however, high ionic conductivities have been found in chemically unstable materials such as CsH2PO4, In-doped SnP2O7, BaH2, and LaH3−2xOx. Here, fast and stable proton conduction in 60-at% Sc-doped barium zirconate polycrystal, with a total conductivity of 0.01 S cm−1 at 396 °C for 200 h is demonstrated. Heavy doping of Sc in barium zirconate simultaneously enhances the proton concentration, bulk proton diffusivity, specific grain boundary conductivity, and grain growth. An accelerated stability test under a highly concentrated and humidified CO2 stream using in situ X-ray diffraction shows that the perovskite phase is stable over 240 h at 400 °C under 0.98 atm of CO2. These results show great promises as an electrolyte in solid-state electrochemical devices operated at intermediate temperatures.
!!!All Science Journal Classification (ASJC) codes