Zr(HPO4)2 based organic/inorganic nanohybrids as new proton conductors

In this study, sulfanilic acid was intercalated into an α-Zr(HPO4)2 with the aim to enhance the proton conductivity via the acidic –SO3H groups. TGA results suggest that intercalation really takes place and a four-day reaction leads to the intercalation of 0.72 guest molecules (sulfanilic acids) per α-Zr(HPO4)2. We find that the hybrid material undergoes three-step decomposition pathways: dehydration (40–150 °C), decomposition of benzene ring (150–470 °C), and finally de-SOx (470–1000 °C). The sulfanilic acid/α-Zr(HPO4)2 hybrid shows a proton conductivity of 2.80 × 10− 3 S/cm, one order higher than the original α-Zr(HPO4)2 (2.04 × 10− 4 S cm− 1) measured at a relative humidity of 100% and 22 °C. The conductivity is strongly dependent on the relative humidity, and sharply increases at over 80% relative humidity. The activation energy for the proton transport in the hybrid is 0.33 and 0.15 eV at 60% and 100% relative humidity, respectively, in the temperature range of 22–100 °C, further reflecting the influence of humidity on the proton conduction.