The Influence of Solution pH on the Kinetics of Resorcinol Electrooxidation (Degradation) on Polycrystalline Platinum

Abstract

Electrochemical oxidation of resorcinol on a polycrystalline platinum electrode was investigated in five different solutions, namely 0.5 and 0.1 M H2SO4, 0.5 M Na2SO4, 0.5 and 0.1 M NaOH. The rates of electrochemical degradation of resorcinol were determined based on the obtained reaction parameters, such as resistance, capacitance and current-density. The electrochemical analyses (cyclic voltammetry and a.c. impedance spectroscopy) were carried-out by means of a three-compartment, Pyrex glass cell. These results showed that the electrochemical oxidation of resorcinol is strongly pH-dependent. In addition, the energy dispersive X-ray (EDX) spectroscopy technique was employed for Pt electrode surface characterization. Additionally, the quantitative determination of resorcinol removal was performed by means of instrumental high-performance liquid chromatography/mass spectrometry (HPLC/MS) methodology.

The Effect of Resorcinol on the Kinetics of Underpotentially Deposited Hydrogen and the Oxygen Evolution Reaction, Studied on Polycrystalline Pt in a 0.5 M H2SO4 Solution

“…On the other hand, Figure 2 presents similar cyclic voltammograms, but reported over the potential range characteristic of the resorcinol (green plot) surface's electrooxidation/degradation (see the wide anodic feature at 1.2-1.5 V here and in [18] for the details of the process). Additionally, it is worth noting that the oxygen evolution reaction commences just beyond ~1.65 V. Most importantly, it should be observed in Figure 2 that the recorded current densities for the RC-based solution are significantly reduced compared with those derived for the corresponding electrode potentials but in the absence of resorcinol.…”

“…Thus, the results recorded in Table 1 (obtained by fitting the data using the equivalent circuit presented in Figure 3B) for the kinetics of UPD of H in pure 0.5 M H2SO4 principally followed those of other data available in the literature (see, for example, [3,22] for details). Thus, the corresponding charge transfer resistance parameter RH (proportional to the inverse of the exchange rate for the process of UPD of H) considerably increased from 0.47 (at 100 mV) to reach 2.65 Ω cm 2 at 400 mV (where H adsorption on the poly Pt surface On the other hand, Figure 2 presents similar cyclic voltammograms, but reported over the potential range characteristic of the resorcinol (green plot) surface's electrooxidation/degradation (see the wide anodic feature at 1.2-1.5 V here and in [18] for the details of the process). Additionally, it is worth noting that the oxygen evolution reaction commences just beyond ~1.65 V. Most importantly, it should be observed in Figure 2 that the recorded current densities for the RC-based solution are significantly reduced compared with those derived for the corresponding electrode potentials but in the absence of resorcinol.…”

“…impedance behaviour of a polycrystalline Pt electrode in a pure 0.5 M H 2 SO 4 solution and in the presence of 1.0 × 10 −5 M RC, examined over the potential range characteristic of the underpotential deposition of hydrogen, is shown in Figure 3A (for a selected electrode potential of 100 mV vs. RHE) and Table 1. The process of UPD of H generates a semicircle over the high and intermediate frequency range in the Nyquist impedance plot, along with a vertical line, which characterizes purely capacitive behaviour (but often deviates from a 90 • angle, due to the so-called capacitance dispersion effect [18,22], related to surface roughness and heterogeneity) at reasonably low frequencies. Thus, the results recorded in Table 1 (obtained by fitting the data using the equivalent circuit presented in Figure 3B) for the kinetics of UPD of H in pure 0.5 M H 2 SO 4 principally followed those of other data available in the literature (see, for example, [3,22] for details).…”

The Fundamental and Underrated Role of the Base Electrolyte in the Polymerization Mechanism. The Resorcinol Case Study

“… 35 , 36 The standard oxidation potential, , of the 1 / 2 redox couple has been calculated at the UB3LYP/cc-pVTZ, resulting in +1.1 V vs Ag/AgCl/KCl sat (compare the Supporting Information for the calculation details), which is a result in fair agreement with the experimental value. 37 …”

“…35,36 The standard oxidation potential, E (1)/(2) 0 , of the 1/2 redox couple has been calculated at the UB3LYP/ cc-pVTZ, resulting in +1.1 V vs Ag/AgCl/KCl sat (compare the Supporting Information for the calculation details), which is a result in fair agreement with the experimental value. 37 Path B is one possible main route for the polymerization reaction, leading to the neutral radical species 3 by the dissociation of the hydroxylic O−H proton: the formation of 3 is a crucial reactive species in the possible polymerization propagation mechanism.…”