Electrochemical and XPS Characterization of Glassy Carbon Electrode Surface Effects on the Preparation of a Monomeric Molybdate(VI)-Modified Electrode

Abstract

Evaluation of electrochemical surface pretreatment methods on the preparation of monomeric molybdate(VI)-modified glassy carbon electrode (GCE) in H2SO4 is studied. The results show that the cathodically treated GCE is unusually highly activated toward Mo(VI) adsorption, but the anodized electrode does not respond, unlike the previous reports for the other adsorbed systems. The analyses of the voltammograms of Mo(VI) on a cathodized electrode show three pairs of reversible peaks with a surface excess on the order of ≅1 × 10-10 mol cm-2 for each of the peaks. The interaction parameters for the three processes are 1.14 × 109, 1.38 × 109, and −5.50 × 109 cm2 mol-1, respectively. Strong interaction between the Mo(VI) ion and cathodically reduced GCE surface groups is indicated by the formation of Mo(V) (detected by x-ray photoelectron spectroscopy (XPS) and electrochemical polarization measurements) during the course of Mo(VI) adsorption at open circuit conditions. The Mo(VI) adsorption via the mixed potential mechanism has been formulated involving Mo(VI) reduction to Mo(V) coupled with surface alcohol group oxidation to hydroperoxide. XPS analyses show that the cathodized surface contains higher amounts of >C−O− surface groups. The quantities of >C−O− surface groups correlate with the observed differences in the response of the pretreated GCE surfaces toward Mo(VI) adsorption.

The effect of downstream plasma treatments on graphene surfaces

“…The situation is further clarified in the XPS spectrum of the same sample shown in Fig.2c. The C1s core level spectrum, fitted in a similar fashion as before, reveals a substantial signal of sp 3 hybridization [47][48][49] along with other carbon functionalities, such as C-N [50,51], C-OH [52,53], C=O [47,52,53], COOH/R [47,52,53], CF-C/C-CF n [54][55][56] as previously reported in the literature. The asymmetry factor on the graphitic peak is increased to 0.1, considerably higher than the as grown sample.…”

Electrode Kinetics of Vanadium Flow Batteries: Contrasting Responses of VII-VIIIand VIV-VVto Electrochemical Pretreatment of Carbon

“…60,[69][70][71][72] For most couples, anodic treatment of a carbon electrode inhibits the redox reaction while cathodic treatment enhances it. Thus, the effects of electrode treatment on V IV -V V are consistent with results for other systems but the contrasting effects on V II -V III are remarkable.…”

Electrocatalytic Reduction and Determination of Dissolved Oxygen at a Preanodized Screen‐Printed Carbon Electrode Modified with Palladium Nanoparticles

“…McCreery et al reported that the N O1s / N C1s ratio can vary in the window of 0.04 to 0.15 under various GCE polishing treatments [25]. Ilangovan and Pillai reported that surface carbon density is an important factor to increase the N O1s /N C1s ratio and it can be improved to 0.51 upon anodization of the GCE surface [26]. The SPE* seems to have a smaller amount surface carbon density over that of GCE, however, the additional chloride peak on the surface can assist for the stabilization of Pd nanoparticles on the SPE*.…”