Ring-disk Electrode Technique Research Articles

A Chronoamperometric Differential Electrochemical Mass Spectroscopy Study on the Growth of Li2O2 and Its Effect on the Mechanism of Oxygen Reduction in Dimethylsulfoxide Based Electrolytes

We report on potential step experiments into the oxygen reduction region in combination with differential mass spectroscopy (DEMS) and the rotating ring disc electrode technique (RRDE). We can thus distinguish between the one electron reduction path leading to superoxide and the 2 electron process leading to lithium peroxide. The evolution of the mass spectroscopic response in the DEMS experiments and evolution of the current at the ring electrode discloses that the deposition of lithiumperoxide hampers the capacity of the electrode for the consecutive transition of two electrons. The latter is required to form Li2O2 on a direct electrochemical pathway. Instead, superoxide becomes the main product of oxygen reduction. A proportionality between coverage with Li2O2 and the share of oxygen reduced to superoxide is observed at platinum. The effect of the Li2O2-deposit is less severe at large overpotentials. However, completion of a single monolayer of Li2O2 on platinum and two monolayers on gold inhibit further oxygen reduction. We suggest that growth of larger Li2O2 structures observed by other authors is caused by a chemical rout to Li2O2 via superoxide disproportionation. Experimental evidence for the latter reaction is provided.In addition, we observe a non-monotonic faradaic current transient typical for nucleation after steps to certain potentials at the gold electrode and ascribe this to the formation of 2D Li2O2. This implies that nuclei of Li2O2 have to form before the solid phase can grow uninhibited. Evidently the involved surface energies cause a crystallisation overpotential and therefore impair the formation of solid Li2O2.

Formation of NiCo2O4 rods over Co3O4 nanosheets as efficient catalyst for Li–O2 batteries and water splitting

A 3D structured NiCo2O4@Co3O4 hybrid was prepared by a two-step hydrothermal approach and subsequently employed as a highly efficient catalyst in oxygen reduction reactions (ORRs)/oxygen evolution reactions (OERs) and from a Li–O2 battery perspective. The Co-NC possesses interconnected NiCo2O4 nanorods grown over a Co3O4 nanosheet structure, which facilitates charge transfer and enhances the electrical conductivity. Moreover, the 3D structured hybrids are directly used as a cathode catalyst for the Li–O2 system and displayed a maximum in-depth-specific discharge capacity of 4386mAhg−1. In addition, significantly improved and stable cycling performance up to 60 cycles is observed compared with Co3O4 nanosheets at the limited capacity range of 500mAhg−1. The excellent electrochemical performance of the NiCo2O4@Co3O4 hybrid is mainly associated with the oxygen-deficient 3D architecture providing more catalytic active sites and can accommodate more discharge products. Further, ORR/OER activities of NiCo2O4@Co3O4 hybrid in aqueous media are also evaluated in 0.1M KOH solution using the rotating ring disk electrode technique. For instance, the OER activity of NiCo2O4@Co3O4 hybrid (apex current is 4.18mAcm−2) is an approximately 2.25 times higher than that of commercial RuO2 catalyst (1.84mAcm−2). Since the catalytic activity in aqueous and organic medium is not necessarily the same, but of NiCo2O4@Co3O4 hybrid exhibiting excellent ORR/OER characteristics in both cases is worth mentioning.

Elucidating the Oxygen Reduction Reaction Kinetics and the Origins of the Anomalous Tafel Behavior at the Lithium–Oxygen Cell Cathode

Development of Li–O2 cells, potentially providing ∼3 times the capacity of Li-ion cells, depends on a fundamental understanding of the oxygen reduction reaction (ORR) at the cathode. The present study investigates the mechanism and kinetics of the oxygen reduction reaction (ORR) on a glassy carbon (GC) electrode in an oxygen saturated solution of 0.1 M lithium bis-trifluoromethanesulfonimidate (LiTFSI) in 1,2-dimethoxyethane (DME) using cyclic voltammetery (CV) and the rotating ring-disk electrode (RRDE) technique. A reaction scheme considering disproportionation of LiO2 on both the cathode surface and the electrolyte bulk to form Li2O2 was proposed, and the RRDE measurements, in conjunction with an electrochemical kinetics model, were used to calculate the corresponding rate constants. The surface disproportionation reaction was found to dominate the kinetics of the ORR, and the model could explain experimental observations regarding the cell discharge products. Further, the widely reported anomalous Taf...

W@Au Nanostructures Modifying Carbon as Materials for Hydrogen Peroxide Electrogeneration

In this work, materials based on core-shell W@Au type structures were found to have promise for use as electrocatalysts on the in-situ production of H2O2 by means of the oxygen reduction reaction (ORR). We describe herein the synthesis and characterization of these materials and then present a study of electrocatalytic activity towards ORR by the electrogeneration of H2O2 employing these materials supported on Vulcan XC-72R carbon corresponding to 1 and 2wt% loading. The use of W@Au/C materials led to higher activity compared to pure carbon and commercial Pt/C, and the optimal load is 1%, which presented the highest ring current for the ORR using the rotating ring-disk electrode technique. Exhaustive electrolysis using a W@Au/C 1% gas diffusion electrode (GDE) was employed to verify the real amount of H2O2 electrogenerated comparing with a Vulcan XC-72R GDE. We verified that the W@Au/C 1% material is able to generate 50% more H2O2 than carbon. These results can be explained based on synergistic interactions presented by the W@Au/C 1% material and also by both conductivity and hydrophilicity differences provided by the nanostructures supported on carbon.

Temperature-dependence of oxygen reduction activity on Pt/C and PtCr/C electrocatalysts synthesized from microwave-heated diethylene glycol method

This work reports first the synthesis of carbon supported Pt and Pt-Cr electrode materials from microwave-heated diethylene glycol (DEG) without additional protective agents. The prepared electrocatalysts have superior electrochemical activity and stability than those previously reported in acidic medium. Transmission electron microscopy (TEM) characterizations of these materials reveal uniformly dispersed particles with a mean size of ca. 1.20nm. The morphological changes of these two materials were investigated by identical location-transmission electron microscopy (IL-TEM) after classical durability test. The electrocatalytic activity towards the oxygen reduction reaction (ORR) was investigated using rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) techniques in 0.1molL−1 HClO4. The kinetic parameters were assessed through the Koutecký-Levich equation at 20, 30 and 40°C. Electrochemical measurements demonstrate that significantly higher catalytic activity was observed on the Pt-Cr/C electrocatalyst than on Pt/C. The RRDE analysis shows that the ORR mainly involves a four-electron reduction mechanism to water with the formation of a very low H2O2 amount as reaction intermediate.

Palladium–nickel materials as cathode electrocatalysts for alkaline fuel cells

In this work, Pd–Ni catalysts supported on carbon nanofibers were synthesized, with metal contents and Pd:Ni atomic ratios close to 25 wt.% and 1:2, respectively. Previously, the carbon nanofibers were chemically treated, in order to create surface oxygen and/or nitrogen groups. The synthesized catalysts displayed low crystallinity degree and high dispersion on carbon supports, especially in those with surface functional groups. Oxygen reduction reaction (ORR) was studied by rotating ring-disk electrode (RRDE) techniques. When the kinetic current is normalized by the mass of Pd present in the electrode, higher activities were obtained for the synthesized materials in comparison with the activity observed for a commercial Pd/C E-TEK catalyst. Some differences are reported for the different materials under study, mainly dependent on the presence of oxygen surface groups on the carbon support. In light of the results, we can propose the synthesized catalysts as possible candidates for cathodes in alkaline direct methanol fuel cells.

A simple strategy to form hollow Pt3Co alloy nanosphere with ultrathin Pt shell with significant enhanced oxygen reduction reaction activity

Pt alloy catalysts, especially alloyed with Fe, Co, Ni, show greatly improved activities for oxygen reduction reaction (ORR) compared with Pt/C. In this work, Co (core)@PtCo (shell) is successfully synthesized based on the successful synthesis of the Co core by wet chemical way. Pt alloy shell is directly formed on Co core by the spontaneous galvanic displacement reaction in acid. The hollow Pt3Co alloy nanospheres are formed when Co@PtCo nanoparticles are treated in 1 mol l−1 sulfuric acid for 8 h. It is thought that the integral and contiguous PtCo alloy shell is important to form the hollow Pt3Co alloy nanospheres. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive X-ray spectroscopy (EDX), are used to characterize crystallite morphology and composition. The ORR activities of the nanoparticles are measured with a rotating ring disk electrode (RRDE) technique. The hollow Pt3Co alloy nanospheres with the size of about 10 nm show approximately 8 times in specific surface area activity and over 4 times in specific mass activity than that of the state-of-the art Pt/C. The electrochemical tests for duration of 5000 cycles at the sweep rate of 100 mVs−1 between 0.6 and 1.0 V (vs. RHE) in O2 saturated electrolyte show that the hollow Pt3Co alloy nanospheres have a remarkable stability. These render the synthesized hollow Pt3Co alloy nanospheres as a promising candidate for the ORR electrocatalyst in Proton Exchange Membrane Fuel Cells (PEMFCs).

Development of a Software to Analyze the Dispersion State of Particles on a Flat Substrate

Functional particles such as TiO2 and Pt/C are often fixed on a flat substrate for practical uses. rotating ring disk electrode (RRDE) technique, in which Pt/C nanoparticles were dispersed on a glassy-carbon (GC) disk electrode, is known as a method capable of evaluating a catalyst activity. The technique was often applied to the evaluation of oxygen reduction catalysts used in fuel cells or metal-air batteries, because the reaction intermediates such as hydrogen peroxide can be detected by the ring electrode. However, the accuracy of the technique was significantly affected by the dispersivity of the catalyst particles on the electrode. Thus, the catalysts on the disk electrode are required to be uniformly dispersed and many researchers have sought the best dispersion method. Although microscope photographic images were used for the estimation of dispersivity on the electrode, no quantitative analyses were performed by using the images. In this study, we have developed a program called “Roughness Analyzer” which can quantitatively analyze the dispersiveness of particles on a flat substrate. This software can load a three dimensional data of particles fixed on a substrate measured by a surface roughness meter (SV-C4500 CNC, Mitutoyo) and display a 2D contour map of the loaded data. It should be noted that, the height of each point is expressed by the brightness of each dot. If necessary, a user can change the range of height represented by the brightness and the number of level. This software is equipped with an auxiliary function to estimate only a substrate surface from a three-dimensional data of the particles fixed on a substrate. This function can automatically determine the points of each cross-section of the 2D contour map that is likely to be surface of the substrate itself, and curves connecting these points was obtained by a spline interpolation method. Thus, only particle-derived height data are calculated by subtracting the height of only the substrate surface data from that of experimental raw data. Analytical functions are “Cluster Analysis” and “Distribution Analysis.” The Cluster Analysis can detect each secondary particle agglomerated on the substrate from the height data. Each secondary particle is filled with a different color and the area, the volume, and the average height of each particle are calculated respectively. The Distribution Analysis can divide the substrate surface in any number from the center of the substrate surface in a radial direction and an angular direction. Further, it can automatically calculate the area, the volume and the percentages of area occupancy of particles in each section. For example, the dispersiveness of a modified GC electrode was evaluated by the software. The electrode was prepared as follows: A 2.0 mg of Pt/MWCNTs was suspended in 1 mL of 0.1 wt% Nafion-EtOH by ultrasonication for 10 min. Then, 10 μL of the suspension was cast onto a glassy-carbon disk (6 mm φ, 0.283 cm2) – Pt ring electrode (Nikko Keisoku) and dried for 1 h at 60°C by using an infrared lamp. Fig. 1 shows the percentage of the area occupancy for the secondary particles in each section. Each cumulative bar represents the percentage of area occupancy in the same radial range, thus, it means good dispersivity of the particles when each cumulative bar has similar height, namely, the standard deviation of the heights is small. Moreover, each element in each cumulative bar means the percentage of area occupancy for the particles at a different angular direction in the same radial range. The desirable dispersivity can be achieved when the standard deviation of the height of the bars is small. However, the small standard deviations are not a sufficient condition for good dispersivity. Criteria for dispersivity are the average height of the particles as well as the standard deviations. Figure 1

A Rotating Ring Disk Electrode Study of the Stability in Different Electrolytes for Lithium-Oxygen Batteries

The electrolyte formula (especially, the composition of organic solvent) is well-known to influence the electrochemical performance of Li-O2 batteries. The electrolyte instability in the battery can be attributed to its reaction with the superoxide radical (O2 • −) produced at the battery’s cathode during discharge. In this work, we have employed the rotating ring disk electrode (RRDE) technique to study the stability of various organic solvents against O2 • − by the quantification of the electrolyte decomposition rate constant (k) for the reaction between various electrolytes and O2 • −. Moreover, RRDE transients are also applied to estimate O2 solubility and diffusion rates of O2 and O2 • − coefficients ( and ) at different electrolytes.

A primary study of the carbon oxidation and oxygen evolution reactions of several carbon materials in a KOH aqueous solution using a rotating ring disk electrode technique

A primary study of the carbon oxidation and oxygen evolution reactions of several carbon materials in a KOH aqueous solution using a rotating ring disk electrode technique

Rudimentary simple, single step fabrication of nano-flakes like AgCd alloy electro-catalyst for oxygen reduction reaction in alkaline fuel cell

In this work, for the first time, we report rudimentary simple, single step fabrication of an electro-catalyst based on AgCd alloy nanoparticles with flakes like geometry which shows highly efficient activity towards oxygen reduction reaction (ORR). A simple potentiostatic deposition method has been employed for co-depositing AgCd alloy nanostructures with flakes like shapes along with dendrites on the surface of carbon fibre paper. The chemico-physical properties of the catalyst are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDXS). Electro-catalytic activity of AgCd alloy based electro-catalyst towards ORR is studied in alkaline medium by cyclic voltammetry and rotating ring disk electrode (RRDE) technique. Electrochemical in-situ FTIR measurements are also performed to identify the species generated during ORR process. Based on the results from electro-catalysis experiment, it is concluded that nano-alloyed AgCd electrodeposited on carbon paper shows excellent activity for ORR, following four electron pathways with H2O2 yield less than 15%. The combination of low cost of Ag and Cd, fast and facile method of its fabrication and higher activity towards ORR makes the AgCd electro-catalyst an attractive catalyst of choice for alkaline fuel cell.

Graphene supported Pt–Ni nanoparticles for oxygen reduction reaction in acidic electrolyte

The design of high performance oxygen reduction reaction (ORR) electrocatalysts play an important role in the commercialization of polymer electrolyte membrane fuel cells. The morphology, structure, and composition of the support material significantly affect the catalytic activity of the fuel cell catalyst. In this work, we report a systematic and comparative study of the effects of the support morphology for Pt–Ni nanoparticles for the ORR. The effect of the support morphology on the electrocatalytic oxygen reduction reaction was investigated. Pt–Ni alloy catalysts were characterized using various physico-chemical techniques, such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Pt–Ni alloy nanoparticles were deposited uniformly on a graphene support and their oxygen reduction activities were evaluated in an acid electrolyte. The ORR activity of Pt–Ni supported on graphene was also compared with Pt–Ni supported on Vulcan carbon XC-72 and carbon nanotubes. The electrocatalytic activity and stability of Pt–Ni alloy catalysts were studied using cyclic voltammetry, linear sweep voltammetry, rotating disk electrode, and rotating ring disk electrode techniques. The results demonstrate that the graphene supported Pt–Ni catalyst showed the highest ORR activity among the three evaluated catalysts.

Ni-doped CoFe2O4 Hollow Nanospheres as Efficient Bi-functional Catalysts

Ni-doped spinel oxides NixCo1-xFe2O4 (x=0, 0.25, 0.5, 0.75) hollow nanospheres electrocatalysts are synthesized with a simple hydrothermal approach. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results reveal that the morphology, hollow and spinel structures of the cobalt ferrites remain unchanged with doping. The electrocatalytic activity of the Ni-doped CoFe2O4 with different doping contents has been studied and compared with the pure CoFe2O4 hollow nanospheres in alkaline solution by using rotating ring-disk electrode (RRDE) technique. For ORR, the Ni0.5Co0.5Fe2O4 (x=0.5) exhibits as the most active catalyst with the highest diffusion limited current density and more positive onset potential. Whereas, the Ni0.75Co0.25Fe2O4 (x=0.75) shows the best catalytic activity for OER with more negative onset potential (0.27V vs. Ag/AgCl) and maximum current density (36.0mA/cm2 at 1.0V). X-ray photoelectron spectra (XPS) measurements reveal that the oxygen vacancy on the oxide surfaces increases, while the cations occupied ratio on octahedral/tetrahedral sites in spinel structures decreases along with the increasing of the Ni doping content. Combining with the charge transfer resistance measured by electrochemical impedance spectroscopy (EIS), these three factors work synergistically on the catalytic activities of the Ni-doped CoFe2O4 hollow nanospheres.

(Invited) Efficient Electrocatalysis of Oxygen Reduction with Metallo-Corroles

The most active non-precious metal catalysts (NPMCs) for oxygen reduction (ORR) to date are the pyrolyzed catalysts, inspired from Heme-like complexes. These are usually composed of iron and/or cobalt coordinated by nitrogens, claimed to resemble the structure of porphyrins and phthalocynines, on the surface of a carbon support. Unfortunately, the exact structure of the catalytic sites remains a mystery and the solution for this conundrum seems be almost impossible. The advantages of using such catalysts are: (1) their high activity and (2) low price, which is derived from the cost of their precursors. The disadvantages are: (1) low durability compared to precious metal catalysts, and (2) their unknown structure, which limits their further improvement in order to obtain both the activity and durability benchmarks needed to become good alternatives for precious metals. One of the most promising options to resolve these issues is to find non-pyrolyzed molecular non-precious metal catalysts for ORR that could be tuned to match the necessary requirements. Recently, Metallo-corroles, a relatively new family of molecular catalysts was reported to have very good potential as non-precious metal catalysts for ORR. The electro-reduction of oxygen was investigated, using a series of first row transition metal β-pyrrole-brominated 5,10,15-tris(pentafluorophenyl)-corroles [M(tpfcBr8), M=Mn, Fe, Co, Ni and Cu] as catalysts in alkaline solutions. The kinetics of the oxygen reduction reaction (ORR) on these catalysts was evaluated using the rotating disk electrode method in a solution of 0.1M KOH. These corroles were adsorbed on a high surface area carbon powder (BP2000) prior to electrochemical measurements, to create a unique composite material. The comparison between the corroles with different metal centers showed a favorable catalytic performance of the ORR in the case of Fe and Co Corroles. The mechanism by which these corroles catalyze the ORR was studied by the rotating ring disk electrode (RRDE) technique, showing that in the case of alkaline solutions, there is a favorable 4 electron transfer mechanism. When comparing the performance of these catalysts in alkaline solutions, to their performance in acidic media, it was clear that the former was substantially higher, both in the onset potentials of the ORR and in the overall kinetic parameters.

Controlling Solution-Mediated Reaction Mechanisms of Oxygen Reduction Using Potential and Solvent for Aprotic Lithium-Oxygen Batteries.

Fundamental understanding of growth mechanisms of Li2O2 in Li-O2 cells is critical for implementing batteries with high gravimetric energies. Li2O2 growth can occur first by 1e(-) transfer to O2, forming Li(+)-O2(-) and then either chemical disproportionation of Li(+)-O2(-), or a second electron transfer to Li(+)-O2(-). We demonstrate that Li2O2 growth is governed primarily by disproportionation of Li(+)-O2(-) at low overpotential, and surface-mediated electron transfer at high overpotential. We obtain evidence supporting this trend using the rotating ring disk electrode (RRDE) technique, which shows that the fraction of oxygen reduction reaction charge attributable to soluble Li(+)-O2(-)-based intermediates increases as the discharge overpotential reduces. Electrochemical quartz crystal microbalance (EQCM) measurements of oxygen reduction support this picture, and show that the dependence of the reaction mechanism on the applied potential explains the difference in Li2O2 morphologies observed at different discharge overpotentials: formation of large (∼250 nm-1 μm) toroids, and conformal coatings (<50 nm) at higher overpotentials. These results highlight that RRDE and EQCM can be used as complementary tools to gain new insights into the role of soluble and solid reaction intermediates in the growth of reaction products in metal-O2 batteries.

Electrocatalytic hydrogen peroxide formation on mesoporous non-metal nitrogen-doped carbon catalyst

Direct electrochemical formation of hydrogen peroxide (H2O2) from pure O2 and H2 on cheap metal-free earth abundant catalysts has emerged as the highest atom-efficient and environmentally friendly reaction pathway and is therefore of great interest from an academic and industrial point of view. Very recently, novel metal-free mesoporous nitrogen-doped carbon catalysts have attracted large attention due to the unique reactivity and selectivity for the electrochemical hydrogen peroxide formation [1–3]. In this work, we provide deeper insights into the electrocatalytic activity, selectivity and durability of novel metal-free mesoporous nitrogen-doped carbon catalyst for the peroxide formation with a particular emphasis on the influence of experimental reaction parameters such as pH value and electrode potential for three different electrolytes. We used two independent approaches for the investigation of electrochemical hydrogen peroxide formation, namely rotating ring-disk electrode (RRDE) technique and photometric UV–VIS technique. Our electrochemical and photometric results clearly revealed a considerable peroxide formation activity as well as high catalyst durability for the metal-free nitrogen-doped carbon catalyst material in both acidic as well as neutral medium at the same electrode potential under ambient temperature and pressure. In addition, the obtained electrochemical reactivity and selectivity indicate that the mechanisms for the electrochemical formation and decomposition of peroxide are strongly dependent on the pH value and electrode potential.

Electrochemical and Computational Study of Oxygen Reduction Reaction on Nonprecious Transition Metal/Nitrogen Doped Carbon Nanofibers in Acid Medium

In this study, we performed both electrochemical measurements, such as the rotating disk electrode and the rotating ring-disk electrode techniques, and density functional theory (DFT) calculations to investigate oxygen reduction reaction (ORR) on nonprecious transition metal/nitrogen doped carbon nanofiber (Fe/N/C and Co/N/C) catalysts in acid medium. The nanofiber catalysts were synthesized by electrospinning and subsequent heat treatment procedures. Our electrochemical measurements showed that the pyrolyzed Fe/N/C catalyst possesses higher activity for ORR than the pyrolyzed Co/N/C catalyst and could promote four-electron (4e−) ORR. In comparison, O2 electroreduction was found to proceed mainly with 2e− pathway on the Co/N/C catalyst. To gain insights into underlying catalytic mechanisms, we calculated the adsorption energies of all possible chemical species and the activation energies for O–O bond dissociation reactions involved in ORR on the FeN4 and CoN4 active sites embedded in graphene. Our DFT cal...

Dealloyed silver nanoparticles as efficient catalyst towards oxygen reduction in alkaline solution

Silver nanoparticles(Ag NPs) were prepared by dealloying Mg-Ag alloy precursor. The obtained Ag NPs have an average ligament size of (50±10) nm. Electrocatalytic activity of Ag NPs towards oxygen reduction reaction( ORR) in 0.1 mol/L NaOH solution was assessed via cyclic voltammetry(CV), rotating ring disk electrode(RRDE) techniques, and electrochemical impedance spectroscopy(EIS). The electrochemical active area for the ORR was evaluated by means of the charge of the underpotential deposition(UPD) of lead(Pb) on Ag NPs. The CV results indicate that Ag NPs have a higher current density and more positive onset potential than the bulk Ag electrode. RRDE was employed to determine kinetic parameters for O2 reduction. Ag NPs exhibit a higher kinetic current density of 25.84 mA/cm2 and a rate constant of 5.45×10–2 cm/s at–0.35 V vs. Hg/HgO. The number of electrons(n) involved in ORR is close to 4. Further, EIS data show significantly low charge transfer resistances on the Ag NPs electrode. The results indicate that the prepared Ag NPs have a high activity and are promising catalyst for ORR in alkaline solution.

Rotating Ring-Disc Electrode Investigation of the Aprotic Superoxide Radical Electrochemistry on Multi-Crystalline Surfaces and Correlation with Density Functional Theory Modeling: Implications for Lithium-Air Cells

The realization of a practical Lithium-air cell depends on understanding the oxygen reduction reaction (ORR), identifying a stable electrolyte and finding a suitable cathode. This study investigates the superoxide radical, its side reactions and correlates density functional theory (DFT) predictions of the surface activity to the experimental kinetics. The ORR on glassy carbon (GC), multi-crystalline Pt and multi-crystalline Au substrates in oxygen saturated 0.1 M Tetraethylammonium Perchlorate (TEAClO4) in Dimethyl Sulfoxide (DMSO) was studied using cyclic voltammetery and the rotating ring-disk electrode (RRDE) technique. The RRDE data was analyzed using kinetic models to understand the electrochemistry of the superoxide radical and calculate the surface reaction rate constants. The percentage of the superoxide radicals detected at the ring from GC, Pt and Au surfaces correlated linearly to the modeled activities of the substrates. Further, the modeled activity trend was found to correlate strongly with the ORR onset potential. This study validates the DFT catalyst screening approach. It also shows that side reactions involving the superoxide radical occurs in fresh, anhydrous DMSO based electrolytes.

水酸化カリウム水溶液中での種々の炭素材料の酸化反応と酸素発生反応に対する回転リングディスク電極法を用いた検討

水酸化カリウム水溶液中での種々の炭素材料の酸化反応と酸素発生反応に対する回転リングディスク電極法を用いた検討