Stability of Superprotonic CsH2PO4 Hermetically Sealed in Different Environments

Using powder X-ray diffraction and AC impedance spectroscopy, we have found that the superprotonic CsH2PO4 (CDP) phase is stable at T = 250 degrees C when sealed in different volumes (15 mL and 50 mL) of dry air or inert gasses. Under these conditions, CDP's proton conductivity stays constant at 2.5 x 10(-2) S center dot cm(-)(1) for at least 10 h. On the other hand, removing the gas from the chamber leads to a sharp, two-order-of-magnitude drop in the proton conductivity. Our data show no evidence of a self-generated water vapor atmosphere in the chamber, and the gas pressure at T = 250 degrees C is several orders of magnitude below the pressures previously used to stabilize CDP's superprotonic phase. These results demonstrate that hermetically sealing CDP in small gas-filled volumes represents a new method to stabilize the superprotonic phase, which opens new paths for large-scale applications of phosphate-based solid acids as fuel cell electrolytes.

Automated summary

Using powder X-ray diffraction and AC impedance spectroscopy, it was found that the superprotonic CsH2PO4 (CDP) phase can be stabilized at 250 degrees C when sealed in dry air or inert gasses. The proton conductivity of CDP remains constant for at least 10 hours under these conditions. However, removing the gas from the chamber leads to a significant drop in proton conductivity.