INDICATOR AND REFERENCE PLATINUM SOLID POLYMER ELECTROLYTE ELECTRODESFOR A SIMPLE SOLID-STATE AMPEROMETRIC HYDROGEN SENSOR

Factors that influence the open-circuit potential of a platinum/solid polymer electrolyte (SPE) electrode in air containing low concentratio ns of hydrogen were investigated. The electrodes were prepared from pl atinum in the form of a wire or a grid mechanically pressed, or a Pt l ayer chemically deposited, onto a Nafion(R) 117 membrane. The paramete r underlying the behaviour of the Pt\SPE electrodes is the ratio of th e rate of reduction of the platinum oxides to the hydrogen transport t hrough a layer adjacent to the electrode surface, which can be control led by, for example, the roughness factor of the platinum electrode. T he lower is this ratio, the more sensitive is the electrode potential to the changes in the hydrogen concentration in the gas phase. Dependi ng on the value of the roughness factor, the Pt\SPE electrode can be e mployed as either an indicator or a reference electrode. The design of a simple amperometric hydrogen sensor, which combines the Pt wire as an indicator electrode and the chemically deposited Pt as a reference electrode, is outlined.