RuO2 electrode surface effects in electrocatalytic oxidation of glucose

Abstract

We have studied the electrocatalytic activity of RuO2-PVC film electrodes, fabricated using RuO2 powders prepared at five different temperatures, viz., 300, 400, 500, 600 and 700 degrees C, for the oxidation of glucose in high alkaline media, 1 to 3 M NaOH. The RuO2-PVC film electrodes have been first characterized in 1 to 3 M NaOH solution by cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques in a wide potential range -1,100 to 450 mV (SCE), and three redox pairs representing Ru(IV)/Ru(III), Ru(VI)/Ru(IV) and Ru(VII)/Ru(VI) transitions have been identified. The voltammetric peaks at low sweep rates have been analyzed using surface activity theory formulated for interacting electroactive adsorption sites, and interaction terms have been evaluated. The total voltammetric surface charges have been analyzed as per Trassatti's formalism with respect to their dependence on potential sweep rate, and charges associated with less accessible and more accessible surface sites have been calculated. For glucose oxidation, the results have indicated that RuO2 (700 degrees C)-PVC electrode shows two oxidation peaks in contrast to RuO2 (300 degrees C)-PVC electrode. Also, RuO2 (700 degrees C)-PVC electrode exhibits higher intrinsic electrocatalytic activity than the 300 degrees C electrode, although the former possesses lower electrochemically active surface area. Additionally, kinetic analyses made from RDE results with reference to Michealis-Menten (MM) enzyme catalysis has shown that RuO2 (700 degrees C) electrode possesses extended glucose-sensing range in terms of MM kinetic constant, K (M) , compared to other electrodes. Possible reasons for such differences in the behavior of the electrodes of different temperatures towards glucose oxidation are identified from studies on oxidation of glucose in solutions of different pH, oxidation of different glucose derivatives, and also from physicochemical results from BET, XRD, SEM, DTGA, XPS analysis of RuO2 powder samples

Electrochemical characterization of praseodymium centers in Pr x Zr1−x O2 zirconias using electrocatalysis and photoelectrocatalysis

“…Linear E p vs. pH plots were obtained for experiments in acetate and phosphate buffers at pH values between 4.0 and 8.0. The slope of such representations for all peaks was 55±10 mV/decade, suggesting, in agreement with literature for the electrochemistry of transition metal oxides [48][49][50], that equal numbers of protons and electrons are involved. Although the standard potential for the process…”

“…(−1.45 V vs. SHE; [51]) would make it possible that a complete reduction to Zr could occur, it is more reasonable to assume a stepwise reduction of the zirconia similar to what has been observed for Ru oxide [52]. The observed rather reversible behavior denotes that the structure of the parent oxide is not seriously affected so that the reduction of zirconias can be described either as a stepwise reduction to different suboxides or the reduction to one suboxide but of differently sized particles.…”

Development of an Enzymeless/Mediatorless Glucose Sensor Using Ruthenium Oxide‐Prussian Blue Combinative Analogue

“…Finally, the catalyst was regenerated back to the active form using an applied potential of 1.06 V (vs. Ag/ AgCl), as shown in Scheme 4, at an electrochemical rate constant of k' ME . Similar kinetic studies have already demonstrated for the ethanol oxidation at mvRuOxRuCN (in acidic solution) [30], glucose oxidation at RuO 2 (in alkaline condition) [11,13], and many biological molecules using lead ruthenate pyrochlore (under wide pHs) [54] Table 3 and earlier MM kinetics results at other RuOx-based systems are also shown for comparison. The catalytic rate constant k c is very close to earlier glucose oxidation results at graphite-epoxy RuO 2 (450 8C) composite and PVC-RuO 2 (300 8C) electrodes at strong alkaline conditions [11,13].…”

“…Ag=AgCl (0.22)] was used for adjusting the potential between E Ag/AgCl and E RHE , so that the pH-dependent ruthenium oxide redox potentials can be compared to the reported standard redox potentials of ruthenium in RHE (where Figure 1A shows the CV responses using PB/SPE, RuOx/ SPE, SPE in 2 mM Ru(CN) 4À 6 , and mvRuOx-RuCN/SPE in the presence and absence of glucose in pH 2 Na 2 SO 4 [45,46], and this is indeed the case for the well-established RuOx mediation in alkaline condition [11,13]. Yet, the mediated oxidation of glucose in acidic media using the mvRuOxRuCN analogue is quite unique and thus it is suspected that different RuOx sites in the mvRuOx-RuCN network may play a role in catalysis.…”

Organic Redox Probes for the Key Oxidation States in Mixed Valence Ruthenium Oxide/Cyanometallate (Ruthenium Prussian Blue Analogue) Catalysts

“…As a result of the disproportion reaction, the oxy/hydroxy-Ru VII always transforms to lower oxidation states when pH < 12 [18 ± 20, 29]. Regarding to the specific redox oxidations, oxy/ hydroxy-Ru VI can oxidize aliphatic alcohols (e.g., ethanol) and formaldehyde in a wide pH range of 1 ± 14 [25, 28, 41 ± 43]; while the oxy-Ru VII can even mediate the carbohydrates (e.g., glucose) and aromatic alcohols (e.g., benzyl alcohol) oxidations under strong alkaline conditions [20,26,27,29,43]. The carbohydrate oxidation was chosen in his study to specific account for the presence of oxy-Ru VII since benzyl alcohol has solubility problem in aqueous solution [43].…”