PERFLUOROSULFONATE IONOMER PHOSPHORUS PENTOXIDE COMPOSITE THIN-FILMS AS AMPEROMETRIC SENSORS FOR WATER

Incorporating H3PO4 in solutions of perfluorosulfonate ionomers (PFSI) significantly improves the sensitivity of electrolytic thin-film PFSI moisture sensors. Stable films are formed with PFSI:H3PO4 ratios greater-than-or-equal-to 5:1, and sensors based on such films have been successfully used to measure moisture levels as low as 2 ppm (dew point -70-degrees-C) with an operating voltage of 15 V. The sensors exhibit fast response times to moisture surge, have no significant hysteresis or flow rate dependence, and are immune to prolonged exposure to very high humidity levels. At high humidities, the sensors also exhibit unusual current-voltage characteristics. In terms of overall cost and performance, such sensors are not only competitive with existing alternatives for low-level moisture measurement but are also the first such devices capable of measuring moisture from low-ppm to saturation levels.