Amperometric Hydrogen Sensor Using Proton Conductor (Antimonic Acid) Thick Film

Abstract

An amperometric solid-state sensor using a proton conductor (antimonic acid) thick film was developed for detecting small amounts of hydrogen in air at room temperature. The thick film (ca.10 μm) was formed on a porous alumina substrate by a spin-coating method (Fig.1). The sensor element had a laminated-type structure in which the thick film was sandwiched by an inner and outer electrodes (sputtered platinum) (Fig.2). The short-circuit current of the sensor was in direct proportion to the hydrogen concentration in the range from 200 ppm to 6000 ppm (Fig.4). The 90% response time to 1000 ppm H2 was as short as 10 s at 30°C (Fig.3). The direction of the current was reversed when the outer electrode was changed from sputterd platinum to platinum black (Figs.3, 7) and this was ascribable to the difference in activity of the electrodes for the electrochemical reduction of oxygen (Fig.5). The large humidity dependence of the current response could be mitigated when the circuitry was modified to include resistance (in series) with the sensor element (Fig.8). The current response in the modified circuitry was also proportional to the hydrogen concentration (Fig.9).