TY - JOUR
T1 - Identification of Mechanistic Subtleties that Apply to Voltammetric Studies at Boron-Doped Diamond Electrodes
AU - Rahman, Md Anisur
AU - Macpherson, Julie V.
AU - Bond, Alan M.
AU - Zhang, Jie
PY - 2020/10/22
Y1 - 2020/10/22
N2 - The α-[S2W18O62]4-/5-and α-[S2W18O62]5-/6-polyoxometalate (POM) reduction processes at boron-doped diamond (BDD) disk electrodes in acetonitrile (0.50 M [n-Bu4N][PF6]) have been investigated using large-amplitude Fourier transformed alternating current (FTAC) voltammetry. The origins of subtle differences in experimental data and simulated data modeled assuming the Butler-Volmer relationship with ion-paring implicitly included, planar diffusion and a uniform surface are considered. Parameters estimated are the apparent heterogeneous electron-transfer kinetics (kapp0′), apparent formal reversible potential (Eapp0′), and apparent charge transfer coefficient (αapp′). The electrode kinetic parameters, in contrast to theoretical predictions of the model employed, are dependent on frequency, POM concentration, and the data analysis method. Reasons for nonconformance to the model include the adsorption of POM on graphite-like sp2-bonded carbon impurities, limitations in the availability of charge carriers in BDD, and the method of incorporating ion pairing when slow electrode kinetics apply. Masking of the sp2 carbon-rich (edge) region of the BDD disk provided FTAC voltammetric data that complied much more closely with the simulated data. Nevertheless, data analysis still produces a concentration dependence in the estimated kapp0′ values, which is considered in terms of the assumption of an infinite number of charge carriers. Conclusions derived from this study are likely to be generally applicable to electrode kinetic investigations at BDD electrodes.
AB - The α-[S2W18O62]4-/5-and α-[S2W18O62]5-/6-polyoxometalate (POM) reduction processes at boron-doped diamond (BDD) disk electrodes in acetonitrile (0.50 M [n-Bu4N][PF6]) have been investigated using large-amplitude Fourier transformed alternating current (FTAC) voltammetry. The origins of subtle differences in experimental data and simulated data modeled assuming the Butler-Volmer relationship with ion-paring implicitly included, planar diffusion and a uniform surface are considered. Parameters estimated are the apparent heterogeneous electron-transfer kinetics (kapp0′), apparent formal reversible potential (Eapp0′), and apparent charge transfer coefficient (αapp′). The electrode kinetic parameters, in contrast to theoretical predictions of the model employed, are dependent on frequency, POM concentration, and the data analysis method. Reasons for nonconformance to the model include the adsorption of POM on graphite-like sp2-bonded carbon impurities, limitations in the availability of charge carriers in BDD, and the method of incorporating ion pairing when slow electrode kinetics apply. Masking of the sp2 carbon-rich (edge) region of the BDD disk provided FTAC voltammetric data that complied much more closely with the simulated data. Nevertheless, data analysis still produces a concentration dependence in the estimated kapp0′ values, which is considered in terms of the assumption of an infinite number of charge carriers. Conclusions derived from this study are likely to be generally applicable to electrode kinetic investigations at BDD electrodes.
UR - http://www.scopus.com/inward/record.url?scp=85096071587&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.0c07431
DO - 10.1021/acs.jpcc.0c07431
M3 - Article
AN - SCOPUS:85096071587
SN - 1932-7447
VL - 124
SP - 24232
EP - 24244
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 44
ER -