OXYGEN-STABLE FERROCENE REFERENCE ELECTRODES

Reference electrodes (RE ′ s) play an important role in electrochemistry, but standard designs suffer from limitations. Ferrocene derivatives have been reported to serve as alternative RE ′ s, but they suffer from poor stability to oxygen, water, and nonaqueous solvents. The previously described ferrocene-based RE ′ s are unstable due to the reaction of ferrocenium ion (Fc+) with dioxygen. We have found that sufficient methyl substitution of the cyclopentadienyl rings can render ferrocenium stable to 02, and ring-methylated Fc+analogues may be used to fabricate stable RE ′ s. A bis(pentamethylcyclopentadienyl)iron reference electrode is described; its potential is pH independent in aqueous buffer solutions. Unlike any other ferrocene electrodes previously reported, these electrodes are stable in aqueous solvents in air. A new reference standard for use under aerobic conditions is proposed. © 1990, American Chemical Society. All rights reserved.