This is a basic content about the types of working electrodes used for electrochemical measurement, their uses, and selection methods, for beginners in electrochemical measurement.
The topics are listed below:
- Part 1: General Remark
- Part 2: Polarizable electrode and nonpolarizable electrode
- Part 3: Metal electrodes such as gold and platinum
- Part 4: Usually used working electrodes & features
- Part 5: Structure of GC & Electrochemical features of basal/edge plane
- Part 6: Glassy carbon electrode surface state characteristics
- Part 7: Glassy carbon electrode surface impurity adsorption and countermeasures
- Part 8: Adsorption of catechol and derivatives on glassy carbon electrode and electron transfer rate
8. Adsorption of catechol and derivatives on glassy carbon electrode and electron transfer rate
Professor Noriyuki Watanabe
The electrochemistry regarding Quinone-hydroquinone including Catechol has been continuously studied for many years and it is an important theme spanning various related fields. Recently there is also an interesting report by D. H. Evans et al. 8-3). Perhaps that story might touch either, relating to carbon electrode surface treatment, this time the introduction subject is also selected from literatures of McCreery et al. (8-1 - 8-2).
As shown in Fig. 8-1, the cyclic voltammogram of 10 µM 4-methylcatechol (pH=1) micro sample has a major feature of diffusive wave on polished only GC electrode, in comparison, on the further pyridine cleaned GC electrode, CV has a major adsorbent wave with a minor diffusive wave in features, the decrease of redox peak potential difference range could be noticed. The catechol adsorption on GC electrode plays an important role in electron transfer, is the theme of this issue. The below two experimental results may support this opinion.
Fig. 8-1 Cyclic voltammograms of 1 µM 4-methylcatechol (pH=1) at polished only and further pyridine cleaned GC electrodes respectively.
For example, on the trifluoromethylphenyl group (TFMP) coated GC electrode, the electron transfer of dopamine (DA) abruptly slows corresponding to TFMP coating ratio increase (It may be found from the significant increase of the peak potential width in Fig. 8-2).
Fig. 8-2 Cyclic voltammograms of 1 mM dopamine in 0.1 M H2SO4 solution on GC electrodes with various TFMP coating ratio (0.12, 0.16, 0.25).
Such an obvious decrease of electron transfer rate may also be achieved by the adsorption of mono-molecules such as methylene blue.
On catechol analogue duroquinone monomolecular adsorbed electrode, the peak potential width of dopamine (comparing with the activated carbon cleaned electrode) has a little increase. On the other hand, the methylene blue monomolecular adsorption is notablely different (Waves at potential range from 200 mV to negative are due to the adsorption of methylene blue and duroquinone in Fig. 8-3). Thus, the adsorption of quinone including adsorption of catechol itself plays a major role in electron transfer of catechol.
Fig. 8-3 Cyclic voltammograms of 1 mM dopamine (pH = 1) on glassy carbon electrodes with different surface treatments (activated carbon cleaned, duroquinone adsorbed and methylene blue adsorbed).
8-1) S.H. DuVall and R.L. McCreery, Anal. Chem., 71, 4594, (1999)
8-2) S.H. DuVall and R.L. McCreery, J. Am. Chem. Soc.,122, 6759, (2000)
8-3) A. Rene and D,H. Evans, J. Phys. Chem. C, 116, 14454, (2012)