Electrochemical Oxidation Of Oxalic Acid Research Articles

Anode material for oxidation of organic acids

It has been proposed to use electrochemical oxidation of oxalic acid to create gas mixtures for calibrating carbon dioxide gas analyzers. The electrocatalytic properties of nickel and tin oxides obtained by thermal oxidation have been investigated. It has been established that the thermally produced tin oxides are of poor quality due to insufficient uniformity. The advantage of the titanium base to the aluminum one has been shown, which is associated with its greater tendency to passivation and stronger adhesion to electrolytic coatings. By the methods of voltammetry, the range of potentials, formed during galvanostatic polarization of oxide-metal electrodes, has been determined. The developed nickel oxide electrodes, formed by thermal oxidation of the titanium-based nickel layer, allow oxalic acid to be oxidized to CO2 with a high current efficiency in the range of current densities of 0.05 … 0.2 A/cm2.

Reduced graphene oxide supported palladium nano-shapes for electro-oxidation of oxalic acid

Size & shape controlled synthesis of metal nanoparticles are of high importance in catalysis. Colloidal techniques offer fine tunings in synthesis process as it involve multiple steps and reaction parameters. An efficient way of producing morphology controlled palladium nanostructures viz. palladium nanocubes (Pd-nc), palladium nanoicosahedrons (Pd-nico) supported on reduced graphene oxide (rGO) and its application in electro-catalysis is reported here. These Pd nano-shapes were achieved via sequential chemical reduction of Pd metal precursor and graphene oxide in the presence of reductant, ethylene glycol (EG) and stabilizer (capping agent), polyvinylpyrrolidone (PVP). Potassium bromide (KBr) and ascorbic acid (AA) were used as structure directing and secondary reducing agents respectively, to tune the geometry of Pd nanoparticles (Pd NPs). The preparation steps were optimized to yield cube shaped Pd nanoparticles (Pd-nc) with mean diameter of 4nm in the presence of KBr/AA; while in their absence, icosahedron shaped Pd nanoparticles (Pd-nico) with mean diameter of 3.1nm were formed and then homogeneously distributed over rGO sheets as evidenced by SEM-EDX and TEM. Further, Pd-nc/rGO and Pd-nico/rGO hybrid composite materials were used to investigate the electrochemical oxidation of oxalic acid (OA) in acidic medium. The results reveal that, these optimal size ranged nanostructures exhibit enhanced electro-catalytic activity when compared to bare glassy carbon electrode (GCE), towards OA oxidation. Among the two, Pd-nico/rGO showed enhanced activity than Pd-nc/rGO. The activity difference was justified based on the particle size distribution and no of surface exposed sites. The synthesis approach provides a versatile route for morphology (shape and size) controlled synthesis of metal nanostructures immobilized on support materials aiming towards fabrication of low cost composites in electro-catalysis and potential sensor applications.

Modified Carbon Paste Electrode In2S3/CPE Nanoparticles for Electrochemical Determination of Oxalic Acid by Cyclic Voltammetry

Abstract Indium sulfide (In2S3) nanoparticles with an average size of ca. 20 nm have been successfully prepared by microwave irradiation. Carbon paste electrode (CPE) was modified with In2S3 and used for the electrochemical oxidation of oxalic acid. Cyclic voltammetry study of the modified electrode indicated that the oxidation potential shifted towards a lower potential by approximately 90 mV and the peak current was enhanced by 2.5-fold in comparison to the bare CPE. The electrochemical behavior was further described by characterization studies of scan rate, pH and concentration of oxalic acid. Using the modified electrode, the calibration curve for oxalic acid was linear in the concentration range from 5.0 × 10−5 to 1.0 × 10−2 mol L−1 with a detection limit of 2.4 × 10−5 mol L−1. Finally, with modified electrode, the content of oxalic acid in spinach was determined.

Biocompatible laponite ionogels based non-enzymatic oxalic acid sensor

An enzyme-free oxalic acid (OA) electrochemical sensor was assembled on indium tin oxide (ITO) plate on which a film of laponite ionogel was coated that resulted in an L/IL/ITO electrode. This ionogel electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectroscopy techniques. Electrochemical oxidation of OA on the electrode surface was investigated by cyclic voltammetry. Further this electrode exhibited high electrochemical activity that yielded well-defined peaks of OA oxidation, and a notably suppressed over-potential compared to the laponite–ITO (L/ITO) electrode. Under optimized conditions, a good linear response (anodic current) was observed for the OA concentration in the 1–20mM range with a detection limit of 3μM. Furthermore, this electrochemical strip sensor presented good characteristics in terms of stability, and reproducibility offering promise of applicability of this green sensor platform.

Hybrid Biotic/Abiotic Catalysts for Oxidation of Complex Biofuels

The electrochemical oxidation of oxalic acid on platinum is one of the main methods explored so far in the design of amperometric sensors for quantitative determination of oxalate and a commonly used approach for wastewater purification and energy production. Apart from that, herein we report the application of various platinum alloys and platinum nanoclusters as catalyst for oxidation of oxalic acid as a final step in the multistep oxidation of various organic compounds, such as fructose, glycerol, glyceric acid, glyceraldehyde, etc. This multistep oxidation processes can involve purely biotic or abiotic catalysts or a hybrid organo/metalo/enzyme catalysts, where the latter along with traditional electrocatalysis takes advantage of bioelectrocatalysis as well. Various PtSn and PtRu alloys were electrochemically evaluated towards the oxidation of oxalic acid in neutral and acidic media (Fig. 1). The onset potential of oxalate oxidation was significantly shifted towards lower potentials for all platinum alloys tested indicating decreased activation energy for the rate-limiting step especially at low pH. Along with the improved thermodynamics of the process, the kinetic of oxalate oxidation was also enhanced when PtSn (1:1) was employed. Density Functional Theory (DFT) calculations were explored to gain a better understanding of the reactivity of the platinum alloys [1]. The mechanism in which two electrons are transferred directly from oxalic acid molecule to the catalyst surface was considered: C2O4H2→*C2O4H + H+ + e-→*CO2H+CO2+H++e-→2CO2+2H++2e- where * represents the active site on the catalyst’s surface. Other mechanisms were also considered, which involve participation of adsorbed species such as OH or O. The free energy diagrams for the oxidation of oxalic acid on Pt based on these mechanisms were calculated using Perdew-Burke-Ernzerhof functional [1]. The results indicate that the adsorption of oxalic acid, which is accompanied by the release of H+and transfer of one electron to the electrode, requires the largest change in the free energy and can be considered as thermodynamically limiting step. Since the adsorption of oxalic acid is the potential-limiting step, an increase in the adsorption energy of oxalic acid on the different platinum alloys can explain the differences in the overpotential observed during the electrochemical evaluation. Based on the DFT calculations it was established that the presence of Sn and/or Ru increases oxalate adsorption and leads to decrease in the overpotential of oxalate oxidation in accordance to the experimentally observed results. DFT also predicted that oxalate oxidation is highly sensitive to the size of the Pt clusters used as a catalyst, imposing the conclusion that decreasing the size of Pt would provide higher activity. Thus, platinum nanoclusters were synthesized using DNA as a template that provides improved cluster stability and were evaluated towards oxidation of oxalic acid. These nanoclusters could be further assembled with aldehyde dehydrogenase to provide multistep catalysis of glyoxalic acid to CO2. In addition, Pt alloys were explored in combination with TEMPO for the subsequent and complete oxidation of glycerol. [1] I. Matanovic, S. Babanova, A. Perry III, A. Serov, K. Artyushkova and P. Atanassov, Bio-inspired design of electrcatalysis for oxalate oxidation: a combined experimental and computational study of Mn-N-C catalyst, Phys. Chem. Chem. Phys., 2015, DOI: 10.1039/C5CP00676G Figure 1

Graphene-supported PtPd Bimetallic Gathered Nanocrystals for Non-enzymatic Sensing of Oxalic Acid.

A novel non-enzymatic oxalic acid (OA) sensor was developed using a nanocrystal PtPd loaded reduced graphene nanosheets (PtPdNCs/RGO)-modified electrode. PtPdNCs/RGO were successfully achieved by a facile, one-step and template-free method, in which PtPd nanoparticles with 100 nm-scale were assembled from polyhedral PtPd nanocrystals of various shapes and dispersed on the graphene nanosheets. Resulting PtPdNCs/RGO were characterized and used for PtPdNCs/RGO-modified electrodes. Electrochemical oxidation of OA on the modified electrode was investigated by cyclic voltammetry and differential pulse voltammetry (DPV). Well-defined peaks of OA oxidation could be obtained using an electrode that indicated its high electrochemical activity. The concentration of OA and the current responses could be obtained in the ranges of 0.5 - 10 and 10 - 35 mM with correlation coefficients of 0.9994 and 0.9952; the detection limit (S/N = 3) was found to be 0.05 mM. The modified electrode presented good characteristics in terms of both stability and reproducibility, promising its applicability in practical analysis.

Tungsten carbide nanotubes supported platinum nanoparticles as a potential sensing platform for oxalic acid.

Supported tungsten carbide is an efficient and vital nanomaterial for the development of high-performance, sensitive, and selective electrochemical sensors. In this work, tungsten carbide with tube-like nanostructures (WC NTs) supported platinum nanoparticles (PtNPs) are synthesized and explored as an efficient catalyst toward electrochemical oxidation of oxalic acid for the first the time. The WC NTs supported PtNPs modified glassy carbon (GC) electrode is highly sensitive toward the electrochemical oxidation of oxalic acid. A large decrease in the oxidation overpotential (220 mV) and significant enhancement in the peak current compared to unmodified and Pt/C modified GC electrodes have been observed without using any redox mediator. Moreover, WC NTs supported PtNPs modified electrode possessed wide linear concentration ranges from 0 to 125 nM and a higher sensitivity toward the oxidation of oxalic acid (80 nA/nM) achieved by the amperometry method. The present modified electrode showed an experimentally determined lowest detection limit (LOD) of 12 nM (S/N = 3). Further, WC NTs supported PtNPs electrode can be demonstrated to have an excellent selectivity toward the detection of oxalic acid in the presence of a 200-fold excess of major important interferents. The practical application of WC NTs supported PtNPs has also been demonstrated in the detection of oxalic acid in tomato fruit sample, by differential pulse voltammetry under optimized conditions.

Non-enzymatic oxalic acid sensor using platinum nanoparticles modified on graphene nanosheets

An enzyme-free oxalic acid (OA) electrochemical sensor was assembled using a platinum nanoparticle-loaded graphene nanosheets (PtNPGNs)-modified electrode. The PtNPGNs, with a high yield of PtNPs dispersed on the graphene nanosheets, were successfully achieved by a green, rapid, one-step and template-free method. The resulting PtNPGNs were characterized by transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and an X-ray diffraction technique. Electrochemical oxidation of OA on the PtNPGNs-modified electrode was investigated by cyclic voltammetry and differential pulse voltammetry methods. Based on the results, the modified electrode exhibited high electrochemical activity with well-defined peaks of OA oxidation and a notably decreased overpotential compared to the bare or even the GNs-modified electrode. Under optimized conditions, a good linear response was observed for the concentration of OA and its current response was in the range of 0.1-15 mM and 15-50 mM with a detection limit (S/N = 3) of 10 μM. Furthermore, the electrochemical sensor presented good characteristics in terms of stability and reproducibility, promising the applicability of the sensor in practical analysis.

Electrochemical oxidation of Methyl Red using Ti/Ru0.3Ti0.7O2 and Ti/Pt anodes

The present study was motivated by a report by Martínez-Huitle et al. in 2005, on the electrochemical oxidation of oxalic acid at a Pt anode in the presence of halide ions in alkaline medium. Addition of halide salts increased the mineralization rate in the order: control<NaCl<NaBr<NaF. Therefore, in this work, the direct and indirect oxidations of an organic model substrate (Methyl Red, MR) using Ti/Ru0.3Ti0.7O2 and Ti/Pt anodes were investigated. Galvanostatic electrolyses of dye solutions led to complete decoloration and total organic carbon (TOC) removal at different operating conditions (current density (j) and temperature). The influence of these parameters was examined, in order to compare the effect of active chlorine and addition of different NaCl concentrations to the dyes solutions during the mediated electrochemical oxidation of MR. Byproducts generated during the direct and indirect MR electrochemical oxidation were identified on the basis of GC–MS results. Chlorinated compounds were produced during mediated electrochemical oxidation, but these were completely eliminated in the final of the process; confirming that this treatment processes can be a suitable alternative for depuration effluents. The findings presented herein are described and discussed in the light of the existing literature data.

Electrochemical Oxidation of Oxalic Acid at Different Anode Materials: Applicability of Electroanalysis for Monitoring OA Degradation

The electrochemical oxidation (EO) of oxalic acid (OA) has been studied, in acidic media at Ti/PbO2, highly boron-doped diamond (BDD), Pt and graphite electrodes by applying 60 mAcm−2 of current density. Generally, EO is monitored by chromatography techniques; but the aim of this work is to show the applicability of electroanalysis for detection of OA concentration during its oxidation; by differential pulse voltammetry (DPV) using two different analytical procedures (by analytical curve and by successive addition standard). The results obtained by DPV analysis showed that OA was oxidized at several substrates to CO2 with different results, showing that the performances of the process dramatically depend on the anodic material. Higher removal efficiencies were obtained at Ti/PbO2, graphite and BDD anodes. Finally, DPV analyses were compared with classic titration method achieving a good fit, confidence intervals and limits. The results are described and discussed in the light of the existing literature.

Electrochemical oxidation of oxalic acid and hydrazinium nitrate on platinum in nitric acid media

Several studies in the literature have investigated the electrochemical effects of oxalic acid and hydrazine on various materials in neutral (pH buffered to 7), basic or weakly acidic media (pH 6). The present work proposes electrochemical techniques that allow for the study of the electrochemical behavior, on a Pt electrode, of oxalic acid and hydrazinium nitrate to better understand their oxidation mechanisms in a nitric acid medium at a pH below 1; in addition, some experiments were carried out to define an electrochemical method that would allow for the simultaneous detection of these species when present within process effluent in very acidic solutions. Some physical data regarding oxalic acid and hydrazinium nitrate were also determined: anodic oxidation of hydrazinium nitrate and oxalic acid were observed at 0.2V and 0.7V (vs. Ag/AgCl), respectively. The diffusion coefficients of hydrazinium nitrate and oxalic acid were found to be 5.2×10−6 and 2.9×10−7cm2s−1, respectively. An experimental design approach demonstrated the influence of nitric acid concentrations on the diffusion coefficients of these species.

Anodic abatement of organic pollutants in water in micro reactors

The electrochemical oxidation of oxalic acid (OA) was performed in a micro flow cell equipped with a boron doped diamond (BDD) anode. This preliminary study demonstrates that a flow cell with a micrometric distance between the cathode and the anode can be used to perform the electrochemical treatment of waters contaminated by organic pollutants in the absence of added supporting electrolytes with high abatements. The effect of the distance between the cathode and the anode, the flow rate and the current density on the abatement of oxalic acid and on the current efficiency was in particular studied.

Electrochemical oxidation of organics in water: Role of operative parameters in the absence and in the presence of NaCl

The electrochemical oxidation of organics in water was investigated theoretically and experimentally to determine the role of several operative parameters on the performances of the process in the presence and in the absence of sodium chloride. Theoretical considerations were used to design the experimental investigation and were confirmed by the results of the electrochemical oxidation of oxalic acid (OA) at boron doped diamond (BDD) or IrO 2–Ta 2O 5 (DSA-O 2) anodes in a continuous batch recirculation reaction system equipped with a parallel plate undivided electrochemical cell. Polarization curves and chronoamperometric measurements indicated that, in the presence of chlorides, the anodic oxidation of OA is partially replaced by an indirect oxidation process. This result was confirmed by electrolyses experiments that show that, in the presence of suitable amount of chlorides, oxidation of OA takes place mainly by a homogeneous process. Interestingly, a very different influence of the nature of the anodic material, the flow rate and the current density on the performances of the process arises in the absence and in the presence of chlorides so that optimization of the two processes requires very different operative conditions. In the absence of chlorides, high current efficiency ( CE) is obtained at BDD when most part of the process is under charge transfer controlled kinetics, i.e. when low current densities and high flow rates are imposed. On the other hand, in the presence of NaCl, higher CE are generally obtained at DSA anode when high current densities and low flow rates are imposed, i.e. when a high concentration of chemical oxidants is obtained as a result of the chloride oxidation. The effect of other operative parameters such as the OA concentration and the pH were further investigated.

Electrochemical oxidation of oxalic acid in the presence of halides at boron doped diamond electrode

Aim of this work is to discuss the electrochemical oxidation of oxalic acid (OA), analyzing the influence of NaCl and NaBr. Experiments were carried out at boron-doped diamond (BDD) electrodes, in alkaline media. BDD electrodes have a poor superficial adsorptivity so their great stability toward oxidation allows the reaction to take place with reactants and intermediates in a non-adsorbed state. The process is significantly accelerated by the presence of a halogen salt in solution; interestingly, the mediated process does not depend on applied current density. Based on the results, bromide was selected as a suitable mediator during OA oxidation at BDD. Br- primarily acts in the volume of the solution, with the formation of strong oxidants; while Cl- action has shown lower improvements in the OA oxidation rate at BDD respect to the results reported using Pt electrode. Finally, the parameters of removal efficiency and energy consumption for the electrochemical incineration of OA were calculated.

Electrochemical oxidation of oxalic acid by Rh octaethylporphyrin adsorbed on carbon black at low overpotential

Abstract We have demonstrated the electrocatalytic oxidation of oxalic acid by carbon-supported Rh octaethylporphyrin at low overpotential in acidic solutions. As a result of C–C bond cleavage, CO2 generation from oxalic acid was clearly verified. The onset potential of oxalic acid oxidation was much lower than those for noble-metals and Co macrocycles. Repeated scans in cyclic voltammetry indicated that oxalic acid oxidation by Rh porphyrins is a stable reaction. Oxalic acid oxidation was suppressed by the presence of halides. The suppression effect of halides increases with increasing the atomic number in order: Br− > Cl− > F−. The reaction rates drastically decreased with an increase in pH of the test solutions. The suppression effect of halides and pH dependence are best explained on the basis of the competitive adsorption of oxalic acid and other anions on Rh(III) octaethylporphyrin.

Electrochemical Oxidation of Oxalic Acid at Highly Boron-Doped Diamond Electrodes

Electrochemical oxidation of oxalic acid has been investigated at bare, highly boron-doped diamond electrodes. Cyclic voltammetry and flow injection analysis with amperometric detection were used to study the electrochemical reaction. Hydrogen-terminated diamonds exhibited well-defined peaks of oxalic acid oxidation in a wide pH range. A good linear response was observed for a concentration range from 50 nM to 10 microM, with an estimated detection limit of approximately 0.5 nM (S/N = 3). In contrast, oxygen-terminated diamonds showed no response for oxalic acid oxidation inside the potential window, indicating that surface termination contributed highly to the control of the oxidation reaction. An investigation with glassy carbon electrodes was conducted to confirm the surface termination effect on oxalic acid oxidation. Although a hydrogen-terminated glassy carbon electrode showed an enhancement of signal-to-background ratio in comparison with untreated glassy carbon, less stability of the current responses was observed than that at hydrogen-terminated diamond.

Gold-nanoparticle-dispersed Boron-doped Diamond Electrodes for Electrochemical Oxidation of Oxalic Acid

Abstract Electrochemical behavior of gold-nanoparticle-dispersed diamond electrodes have been studied for the oxidation of oxalic acid in phosphate buffer solution. Comparison is made with gold, as-deposited diamond and gold-implanted diamond. The electrodes combine the high catalytic activity of gold and the low background current of diamond electrodes. Moreover, the electrodes can overcome the problem of stability as it is found when using other electrodes.

In situ preparation of Co phthalocyanine on a porous silica gel surface and the study of the electrochemical oxidation of oxalic acid

In situ preparation of Co phthalocyanine on a porous silica gel surface and the study of the electrochemical oxidation of oxalic acid

Electrochemical incineration of oxalic acid: Role of electrode material

The electrochemical oxidation of oxalic acid (OA) has been studied, in acidic media, at Ti/PbO 2, highly boron-doped diamond (BDD), Pt, Au and Ti/IrO 2–Ta 2O 5 electrodes, by both cyclic voltammetry and bulk electrolysis. The anodic oxidation of OA has clearly shown that the electrode material is an important parameter when optimizing such processes, since the mechanism and the products of several anodic reactions are known to depend on the anode material. OA was oxidized at several substrates to CO 2 with different results; however, higher current efficiencies were obtained at Ti/PbO 2, Pt and BDD. At Ti/PbO 2, the carboxylic groups are expected to strongly interact with the Pb (IV) sites and the hydroxyl radical formed on/at the electrode surface. In some cases, complex interactions exist between the organic substrate and the electrode surface, as confirmed by the oxidative behavior of OA at the Pt electrode.

Size effects on the electrochemical oxidation of oxalic acid on nanocrystalline platinum

Abstract The electrocatalytic activity of platinised platinum (Pt ∣ Pt) electrodes in the electrooxidation of oxalic acid was found to be dependent on the degree of ageing. Pt ∣ Pt electrodes prepared by electrodeposition were aged by cycling the potential with an upper positive potential limit corresponding to Pt surface oxidation. This procedure results in surface reconstruction with an increase of mean particle size. The changes of surface area and roughness of Pt ∣ Pt during ageing have been discussed in terms of sintering processes for supported catalysts or ceramic materials. An increase of mean particle size is accompanied by a decrease in oxygen adsorption, e.g. through changes in the surface concentration of defects on the particle surface. Two possible mechanisms for the electrooxidation of oxalic acid involving either an oxygen adsorbate species (CE mechanism) or direct electrode transfer can be distinguished. Changes of oxidation rate are related to changes of oxygen coverage with ageing.