Zr(HPO4)(2) based organic/inorganic nanohybrids as new proton conductors
In this study, sulfanilic acid was intercalated into an alpha-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 alpha-Zr(HPO4)(2). We find that the hybrid material undergoes three-step decomposition pathways: dehydration (40-150 degrees C), decomposition of benzene ring (150-470 degrees C), and finally de-SOx (470-1000 degrees C). The sulfanilic acid/alpha-Zr(HPO4)(2) hybrid shows a proton conductivity of 2.80 x 10(-3) S/cm, one order higher than the original alpha-Zr(HPO4)(2) (2.04 x 10(-4) S cm(-1)) measured at a relative humidity of 100% and 22 degrees 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 degrees C, further reflecting the influence of humidity on the proton conduction.