Novel Highly Dispersed Additive for Proton-Conducting Composites

Abstract

The proton conductivity and structural properties of (1–x)CsH2PO4–xZnSnO3 composites with compositions of x = 0.2–0.8 were studied. Zinc stannate ZnSnO3 was prepared by the thermal decomposition of zinc hydroxostannate ZnSn(OH)6, which was synthesized by hydrolytic codeposition. To optimize the microstructure of ZnSnO3, thermal decomposition products of ZnSn(OH)6 were characterized by thermal analysis and X-ray diffraction, Fourier transform infrared spectroscopy, low-temperature nitrogen adsorption, and electron microscopy. The study reveals that the thermolysis of ZnSn(OH)6 at temperatures of 300–520 °C formed an X-ray amorphous zinc stannate with a high surface area of 85 m2/g possessing increased water retention, which was used as a matrix for the formation of the composite electrolytes CsH2PO4–ZnSnO3. The CsH2PO4 crystal structure remained in the composite systems, but dispersion and partial salt amorphization were observed due to the interface interaction with the ZnSnO3 matrix. It was shown that the proton conductivity of composites in the low-temperature region increased up to 2.5 orders of magnitude, went through a smooth maximum at x = 0.2, and then decreased due to the percolation effect. The measurement of the proton conductivity of the ZnSnO3–CsH2PO4 composites revealed that zinc stannate can be used as a heterogeneous additive in other composite solid electrolytes. Therefore, such materials can be applied in hydrogen production membrane reactors.