Fabrication of a Palladium Hydride pH Microelectrode with an Extended Lifetime

Abstract

Stable miniaturized pH microelectrodes are crucial in exploring localized pH changes, but most suffer from instability and short lifetimes. Palladium hydride in a mixer phase has been reported to measure the solution pH taking advantage of the interaction between the alloyed hydrogen atoms and hydrogen ions in the solution. However, with the escape of the hydrogen atoms from the palladium lattice, the palladium hydride will transition to single phase and become invalid for pH measurement. The duration of the mixer-phase palladium hydride is even shorter as the sensor is made small. A method to stabilize the mixer-phase is needed for the development of palladium hydride sensors.A method of synthesizing the mixer-phase palladium hydride in dimethylformamide at an elevated temperature has been reported. The synthesized palladium hydride can be stable under aerobic conditions. We used the stable palladium hydride to fabricate a pH microelectrode. In contrast to electrochemically generated palladium hydride microelectrodes, chemically generated palladium hydride microelectrodes are longer lasting and importantly have good an analytical performance under aerobic conditions. Chemically generated palladium hydride microelectrodes perform best in acid to neutral electrolytes devoid of Cl-. They can readily be produced on 10 µm diameter disk platinum microelectrodes, which makes them attractive candidates for future localized electrochemical studies.