Potentiometric measurement of state-of-charge of lead-acid battery by using a bridged ferrocene surface modified electrode

Alkanethiol bridged, 3-(11-mercaptoundecyl)[3](1,1′) ferrocenophane and 3-(11-mercaptoundecyl)[5](1,1′) ferrocenophane were synthesized and their electrochemical behaviour in aqueous sulphuric acid electrolyte investigated. It is found that these compounds, chemisorbed on a gold substrate, undergo reversible electrochemical oxidation/reduction. The anodic and cathodic peak potentials are independent of the acid concentration in the range 1.0 × 10−2 to 1.0 × 10−7 M but change linearly with the acid concentration in the range 1–5 M. While this behaviour is similar to that for other ferrocenes like [3](1,1′) ferrocenophane and [5](1,1′) ferrocenophane the materials are much more chemically stable in aqueous sulphuric acid media. The presence of thiol group enhances the retainability of the bridged ferrocene while maintaining its chemical stability. The possibility of applying this observation for determining state-of-charge of lead-acid battery is discussed.