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

Abstract

[3 }(J,l ') ferrocenophane, [S}(J, J ') ferrocenophane, BSFc (II), 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 oxidation/reduction. The anodic and cathodic peak potentials are found to be independent of the acid concentration in the range IntroductionThe ferrocene/ferricinium (Fc/Fc +) couple is a well known reference electrode for electrochemical studies [1, 2]. It is based upon the fact that ferrocene undergoes a reversible redox reaction according to Eq 1 which, does not involve H+ ions.Hence the redox potential of the FcfFc+ couple is independent of H+ concentration. However the ferricenium cation is soluble in aqueous solutions and is susceptible to various decomposition reactions. This instability limits the use of FcfFc+ couple in electrochemical sensors and other devices for use in aqueous media. We reported earlier [3] that the solubility and instability of FclFc+ in aqueous media could be overcome by using ferrocene derivatives in which the two cyclopentadienyl rings are bridged by hydrocarbon chains consisting of methylene groups fCH2fn where n=3 or 5. We found that such bridged ferrocenes (BFc), were chemically stable but could not be efficiently retained at the surface of an inert substrate [3]. Thus such ferrocene derivatives were not suitable for making appropriate surface modified electrodes (SME's).With the view to improving the retainability of the BFc at electrode surface, we have considered incorporation of alkanethiol [fCH2fllSH] groups into the bridged ferrocene molecule (BSFc). The sulphur atom in the -SH group of BSFc is expected to have a strong interaction with metals like gold [4]. Hence coating gold with BSFc could be the way to construct a robust SME for use in aqueous media. This paper describes the results of a systematic study of the electrochemistry, and chemical stability of BSFc in concentrated (1-5 M) aqueous H2S04 media. The underlying objective of the work was to investigate whether the BSFcfBSFc+ couple could be used as a SME for monitoring changes in H 2 S04 concentration which in turn could be used for determining state of charge of Lead-acid batteries. 140 ExperimentalAll solutions were prepared by dissolving commercially available analytical grade chemicals in high purity water obtained from a Millipore Milli-Q system. All the chemicals were used as received. The ferrocene derivatives ( Figure 1) were synthesized in our laboratory by using standard techniques as reported in the literature [5][6][7][8]. A polycrystalline gold electrode (99.99% fine gold; Australian Gold Refineries, Perth.) was used as a substrate. BSFc coated on gold SME's were prepared by adopting a procedUre similar to that reported in the literature [9]. The gold surface was cleaned by polishing with silicon carbide waterproof papers grades 800, 1200, followed by dipping into aqua regia for 1 minute. The cleaned electrode was then potentio...

Redox-Stable SAMs in Water (pH 0–12) from 1,1′-Biferrocenylene-Terminated Thiols on Gold

“…In conclusion, we confirm the rapid decomposition of Fc-SAMs in aqueous solution, as documented several times in the literature. ,− In all previous publications, the decomposition of the surface-confined Fc was attributed to an irreversible reaction of the ferrocenium cation with nucleophiles: e.g., hydroxide or chloride. Even the mild nucleophilic perchlorate ion was observed to decompose ferrocene SAMs after oxidation.…”

“…The ferrocene unit not only serves as a redox probe to explore fundamental properties of SAMs but also increasingly is utilized in various biomedical and technical applications operating under physiological conditions. In principle, though, the extensive utilization of ferrocene is contraindicated by the notorious instability of the ferrocenium cation (Fc + ) in aqueous solutions, even at acidic pH and under surface-confined conditions. ,, The fundamental instability of the ferrocenium redox stage in aqueous media limits its relevance for many biological and medical redox applications, because any reliable and quantitative data acquisition under physiological conditions with high ion content will require full stability, especially toward ubiquitous nucleophiles, such as hydroxide and/or chloride.…”

Polydivinylferrocene surface modified electrode for measuring state-of-charge of lead–acid battery

“…Accordingly, we are exploring the possibility of using organic redox couples with the view to developing a miniaturised device capable of monitoring H 2 SO 4 concentration as a function of state-of-charge of a lead-acid battery. In continuation of our previous work, [2][3][4][5][6][7][8][9][10][11][12], where we investigated several ferrocene derivatives, we report in this paper the results of our findings on polydivinylferrocene (PDVF). In the past, we have examined the following polymeric ferrocenes:…”