Rotating Disk Electrode Method Research Articles

C(Mo2C) and Pt–C(Mo2C) based mixed catalysts for oxygen reduction reaction

The mixed catalysts were prepared by mechanical mixing of the synthesized 60 wt.% Pt–C(Mo2C) (with average Pt nanoparticle size ~ 5 nm) with unmodified carbon powder (synthesized from molybdenum carbide (Mo2C)) to receive the following compositions of the catalysts: 1:1, 1:2, 1:5 60 wt.% Pt–C(Mo2C):C(Mo2C), respectively. The electrochemical characteristics for various micro- and mesoporous carbon based catalysts have been established by cyclic voltammetry and rotating disk electrode methods. Oxygen electroreduction characteristics for the mixed catalysts were compared with the 60 wt.% Pt–C(Mo2C) electrode and with respective 1:1 20 wt.% Pt–C(Mo2C):C(Mo2C) data. Experiments in KOH aqueous solution show that the additionally added carbon powder plays a weak role in Pt–C(Mo2C):C(Mo2C) mixed catalysts increasing the capacitive current densities and shifting the half-wave potential toward more negative values.

Rationalizing the Influence of the Mn(IV)/Mn(III) Red-Ox Transition on the Electrocatalytic Activity of Manganese Oxides in the Oxygen Reduction Reaction

Knowledge on the mechanisms of oxygen reduction reaction (ORR) and descriptors linking the catalytic activity to the structural and electronic properties of transition metal oxides enable rational design of more efficient catalysts. In this work ORR electrocatalysis was studied on a set of single and complex Mn(III) oxides with a rotating disc electrode method and cyclic voltammetry. We discovered an exponential increase of the specific electrocatalytic activity with the potential of the surface Mn(IV)/Mn(III) red-ox couple, suggesting the latter as a new descriptor for the ORR electrocatalysis. The observed dependence is rationalized using a simple mean-field kinetic model considering availability of the Mn(III) centers and adsorbate-adsorbate interactions. We demonstrate an unprecedented activity of Mn2O3, ca. 40 times exceeding that of MnOOH and correlate the catalytic activity of Mn oxides to their crystal structure.

Benchmarking the oxygen reduction reaction activity of Pt-based catalysts using standardized rotating disk electrode methods

Thin-film rotating disk electrodes (TF-RDEs) have become the preferred half-cell technique for screening small lab-scale quantities of electrocatalysts targeted for proton exchange membrane fuel cells. Utilizing standardized protocols and best practices for Nafion-based catalyst layer fabrication, we demonstrate that catalyst layers fabricated with the rotational air drying technique result in improved film quality and ∼1.6× higher ORR activity as compared to the conventional stationary air drying technique for PtCo/C catalysts. The ORR activity of a series of candidate Pt-based electrocatalysts having improved kinetics (Pt-alloys), corrosion-resistance carbon supports, various Pt wt% and the implications for practical proton exchange membrane fuel cells (PEMFCs) is discussed.

Influence of Temperature on the Oxygen Electroreduction Activity at Nanoporous Carbon Support

Influence of temperature on the oxygen reduction kinetics of various catalysts has been analyzed in O2 saturated 0.1M KOH solution using rotating disc electrode method. Several important reaction parameters, such as the number of electrons transferred per one oxygen molecule, the slope values of Tafel-like plots at different temperatures, and the apparent activation energies for the oxygen reduction reaction were obtained. The calculated absolute kinetic current density value (62.6 A m-2) at the half-wave potential (-0.05V vs. HgêHgOê0.1M KOH) of platinum nanoparticles modified catalyst was maximum at 60oC. Calculated apparent activation energies were within a range from 19 to 27 kJ mol-1 at Pt nanoparticles modified molybdenum carbide derived carbon catalyst within potential range from 0.05 to -0.07V vs. HgêHgOê0.1M KOH.

Pd/Ni Synergestic Activity for Hydrogen Oxidation Reaction in Alkaline Conditions

The investigation of hydrogen oxidation reaction (HOR) in alkaline conditions has been the subject of a wide interest in the past few years with the rise of alkaline membrane fuel cells (AMFCs). In particular, the quest for the lowest content of platinum group metals (PGMs) in the HOR catalyst is ongoing. In this article, we propose the use of a nanoscale Pd layer partially covering a Ni film to provide the most efficient use of the PGM in the HOR catalyst. The Pd/Ni electrodes were prepared by spontaneous and electrolytic deposition of Pd onto smooth polycrystalline Ni surfaces with different surface compositions. The electrodes were characterized by cyclic voltammetry and atomic force microscopy. Electrocatalytic activity in HOR of the Pd/Ni electrodes was measured in alkaline solution by rotating disc electrode method. In the manuscript, we demonstrate that a Pd coverage as low as 1.5% vs. Ni coverage is sufficient to provide a high current density compared to pure Ni. The current density linearly increases with the Pd coverage up to a Pd coverage of 17%; upon further increase in the Pd coverage, the current density reaches a plateau, i.e. the diffusion limit for the HOR process. The comparison with Pd supported on carbon shows the clear benefit for the bimetallic catalyst.

Effect of Alloy Composition on Electrocatalytic Activity of PdAu Core/Pt Shell Nanoparticle Catalysts for Oxygen Reduction Reaction

Introduction Reducing the Pt consumption in electrocatalyst for polymer electrolyte fuel cells or improving mass activity of Pt (MAPt) for oxygen reduction reaction (ORR) is significant. The core/shell catalysts whose shell is a Pt monolayer can greatly improve the MAPt for ORR. Recently, we have succeeded in the preparation of Pd nanoparticles (NPs) loaded-carbon black catalysts (Pd/CB) with ca. 4.2 nm in mean size by using CO as a reducing agent in acetonitrile solution containing Pd(CH3COO)2.1 The MAPt at 0.9 V vs. RHE of Pd core/Pt shell catalyst using Pd/CB as a core (Pt/Pd/CB) was about 5 times as high as that of the commercial Pt/CB (Pt/CB-TKK, TEC10E50E). Wang et al. reported that the surface Pt-Pt distance strongly influenced ORR activity for core/shell catalysts which consisted of various core metals and a Pt monolayer.2 So, the MAPt of Pt/Pd/CB higher than Pt/CB-TKK can be ascribed to more appropriate surface Pt-Pt distance. The optimization of the surface Pt-Pt distance must be required for the maximization of ORR activity. It is known that the surface Pt-Pt distance of the Pt shell depend on the atomic radius of core metal.3 In this study, we attempt to adjust alloy composition of PdAu alloy core NPs to optimize the surface Pt-Pt distance or maximize ORR activity of Pt/PdAu/CB catalysts. Experimental The PdAu alloy NPs were prepared by bubbling CO in acetonitrile solutions containing Pd(CH3COO)2 and KAuCl4 at 4 °C, and loaded on CB (Pd100-xAux/CB, x=5, 10, 20). Then the concentration of precursors was changed to 0.25~2 mM to control particle size of PdAu NPs. The content of PdAu NPs in the Pd100-xAux/CB was 30 wt. %. A monolayer of Pt shell was deposited on the PdAu NPs by Cu-underpotential deposition and then galvanic replacement (Pt/Pd100-xAux/CB, x=5, 10, 20).1, 3, 4 For Pd100-xAux/CB, the core size was evaluated by transmission electron microscope (TEM). To evaluate electrochemical properties of the Pd100-xAux/CB and Pt/Pd100-xAux/CB catalysts, a Nafion-coated GC disk electrode was prepared according to the previous procedure.1 The ORR activity for the Pt/Pd100-xAux/CB was evaluated in an O2-saturated 0.1 M HClO4 aqueous solution at 25 ºC by rotating disk electrode method. Durability against Pt dissolution of the Pt/Pd100-xAux/CB was tested using square-wave potential cycling between 0.6 V for 3 s and 1.0 V for 3 s at 60 °C.1 Results and Discussion Fig. 1 shows the relationship between the nearest neighbor interatomic distance and alloy composition of Pd100-xAux/CB. The nearest neighbor interatomic distance was evaluated with Vegard law. From the XRD patterns of Pd100-xAux/CB (Fig 1), the diffraction peak assigned to Pd(111) was shifted to lower angle when Au content was increased. The nearest neighbor interatomic distance of Pd100-xAux/CB was increased with the Au content, but it deviated from the Vegard law. From TEM, mean particle size of Pd100-xAux/CB was ca. 4.2 nm irrespective of the Au content. Fig. 2 shows the MAPt and specific activity of Pt (SAPt) at 0.9 V vs. RHE for the Pt/Pd100-xAux/CB electrodes. Fig. 2 exhibited there was a volcano relationship between MAPt or SAPt and the changed due to Au content of Pt/Pd100-xAux/CB, suggesting that the surface Pt-Pt distance could be optimized by controlling the alloy composition. Pt/Pd90Au10/CB exhibited the highest MAPtin this study, which was approximately 8 times as high as that of Pt/CB-TKK. Acknowledgement This work was supported by New Energy and Industrial Technology Development Organization (NEDO) through the industrial technology research grant program (08002049-0). References R. Sakai, M. Chiku, E. Higuchi, H. Inoue, ECS Trans., 41, 2211 (2011).X. Wang, Y. Orikasa, Y. Takesue, H. Inoue, M. Nakamura, T. Minato, N. Hoshi, Y. Uchimoto, J. Am. Chem. Soc., 135, 5938 (2013). J. Zhang, Y. Mo, M. B. Vukmirovic, R. Klie, K. Sasaki, R. R. Adzic, J. Phys. Chem. B, 108, 10955 (2004)J. Zhang, M. B. Vukmirovic, Y. Xu, M. Mavrikakis, and Radoslav R. Adzic, Angew. Chem. Int. Ed., 44, 2132 (2005). Figure 1

Pdpt Alloy Nanocubes As Electrocatalysts for Oxygen Reduction Reaction in Acid Media

Platinum-based catalysts are the best electrocatalysts for oxygen reduction reaction (ORR) in fuel cells.1 However, because of the high price and limited supply of Pt, numerous researches have focused on finding a way to reduce its amount in the catalysts. One way to decrease Pt loading is to replace it partially by other metals. Pd is a promising substitute due to the similar properties to the Pt (same group of the periodic table, similar atomic size and crystalline structure).2 In this work, PdPt alloy nanocubes with different metal ratios were synthesized in the presence of polyvinylpyrrolidone.3 The surface morphology of the PdPt samples was characterized by transmission electron microscopy (TEM). TEM images showed that PdPt nanoparticles were cubic-shaped and the average size of the cubes was about 8–10 nm. TEM image for sample Pd54Pt46 is shown in Fig. 1a. Electrochemical measurements were performed to explore the electrocatalytic properties of the PdPt alloy nanocubes toward the ORR in 0.5 M H2SO4 using the rotating disk electrode (RDE) method. CO stripping and cyclic voltammetry (CV) were used for cleaning and characterizing the surface of catalysts. The CV responses showed improvement in surface cleanness after CO oxidation compared with those CVs initially measured. Comparison of polarization curves received from RDE measurements at 1900 rpm are presented in Fig. 1b. The half-wave potentials (E 1/2) for O2 reduction on PdPt alloys were found to be higher than that of Pd nanocubes and were comparable with that of Pt nanocubes. The onset potential for Pd36Pt64 was the highest. The RDE data were analyzed using the Koutecky-Levich (K-L) equation and from the slopes the number of transferred electrons (n) was found. The value of n was close to four for all the catalysts studied. For better comparison of the kinetic parameters of all the electrodes the Tafel plots were constructed from the RDE data (Fig. 1c). Two regions with distinct slope values were observed. In the low overpotential region the slope value was close to -60 mV dec‒ 1 and at high overpotentials the Tafel slope value was over -130 mV dec‒ 1. All the alloyed catalysts showed enhanced electrocatalytic activity for ORR as compared to the monometallic cubic Pd nanoparticles. From the alloyed catalysts Pd36Pt64 exhibited the highest specific activity, which was only slightly lower than that of cubic Pt nanoparticles. Work is in progress to study the electroreduction of oxygen on PdPt alloy nanocubes in 0.1 M KOH solution using the RDE method. Single-waved polarization curves with well-defined current plateaus were observed. The E 1/2 values for PdPt alloys in alkaline solution were comparable. The K-L analysis showed that O2 reduction on these alloys proceeds via 4-electron pathway in 0.1 M KOH. The Tafel analysis revealed that the mechanism of O2 reduction on PdPt alloy nanocubes in alkaline media is similar to that in acid media. The PdPt alloy nanocubes exhibit good electrocatalytic activity for the electroreduction of oxygen in both electrolytes. This indicates a great promise of these materials as cathode catalysts for low-temperature fuel cells.

PdPt alloy nanocubes as electrocatalysts for oxygen reduction reaction in acid media

In this work, PdPt alloy nanocubes with different metal ratios were synthesised in the presence of polyvinylpyrrolidone (PVP). The surface morphology of the PdPt samples was characterised by transmission electron microscopy (TEM). TEM images showed that PdPt nanoparticles were cubic-shaped and the average size of the cubes was about 8–10 nm. Their electrocatalytic activity towards the oxygen reduction reaction (ORR) was studied in 0.5 M H2SO4 using the rotating disc electrode method. All the alloyed catalysts showed enhanced electrocatalytic activity for ORR as compared to the monometallic cubic Pd nanoparticles. Half-wave potential values for PdPt catalysts were comparable with that of Pt nanocubes. From the alloyed catalysts Pd36Pt64 exhibited the highest specific activity, which was only slightly lower than that of cubic Pt nanoparticles. The Koutecky–Levich analysis revealed that the reduction of oxygen proceeded via 4-electron pathway on all the electrocatalysts studied.

Electrocatalytic Activity for Oxygen Reduction Reaction of Au Core/Pt Shell Nanoparticle-Loaded Carbon Black Catalyst with Different Core Sizes

Au core/Pt shell nanoparticle-loaded carbon black catalysts were prepared by forming a Pt monolayer on newly prepared Au nanoparticles and their electrocatalytic activities for the oxygen reduction reaction (ORR) were evaluated by the rotating disk electrode method. The Au nanoparticles were prepared by bubbling CO as a reducing agent in KAuCl4 aqueous solutions containing glutathione (GSH) as a stabilizer, and GSH on the resultant Au nanoparticles was removed by electrochemical oxidation. Underpotential deposition of Cu on the electrochemically treated Au nanoparticles (AuG-ET) and subsequent galvanic displacement of Cu with Pt led to the production of Au core/Pt shell nanoparticle-loaded carbon black (AuG-ET@Pt). In the X-ray photoelectron spectra, the S0 peak of AuG-ET completely disappeared, while the Au0 peaks returned to their intrinsic positions. From transmission electron microscopy images, particle size of Au on AuG-ET was 2.5±0.5nm. These results indicate that GSH was completely removed from the Au surface without increasing the size. The Pt coverage of AuG-ET@Pt was 0.95. The electrocatalytic activity per unit mass of Pt (MAPt) at 0.9V vs RHE for the AuG-ET@Pt was 1.3 and 6.6 times higher than that for our previous Au@Pt of 2.8±0.5nm in size and commercial Pt/carbon black, respectively. Reducing the size of the Au nanoparticles can increase MAPt. After durability test, the particle size and standard deviation of AuG-ET@Pt were 3.9±0.9nm, which were larger than the initial values (3.0±0.5nm), leading to the decrease in specific surface area of Pt.

Oxygen Electrocatalysis on High-Surface Area Non-Pt Metal Modified Carbon Catalysts

Series of carbon supported non-noble d-metal Fe or d-metal-nitrogen (Fe-N- or Co-N-) nanocluster activated electrocatalysts have been synthesized by sodium borohydride reduction method. Synthesized d-metal-nitrogen carbon catalysts were studied using X-ray diffraction, scanning electron microscopy, time of flight secondary ion mass-spectrometry and Raman spectroscopy methods. The electrochemical parameters of synthesized catalysts were investigated in alkaline media using cyclic voltammetry and rotating disk electrode methods. The high catalytic activity toward oxygen electroreduction reaction was demonstrated and found to be increasing in the following order: Fe-Vulcan; Co-N-Vulcan; Co-N-C(Mo2C); Fe-N-C(Mo2C). The possibility to replace the Pt metal catalyst with non-noble metal–nitrogen carbon electrocatalyst has been discussed.

Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy.

The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. The identification of the reaction descriptor is therefore of critical importance for the rational catalyst design and development. Here we report the correlation between hydrogen oxidation/evolution activity and experimentally measured hydrogen binding energy for polycrystalline platinum examined in several buffer solutions in a wide range of electrolyte pH from 0 to 13. The hydrogen oxidation/evolution activity obtained using the rotating disk electrode method is found to decrease with the pH, while the hydrogen binding energy, obtained from cyclic voltammograms, linearly increases with the pH. Correlating the hydrogen oxidation/evolution activity to the hydrogen binding energy renders a monotonic decreasing hydrogen oxidation/evolution activity with the hydrogen binding energy, strongly supporting the hypothesis that hydrogen binding energy is the sole reaction descriptor for the hydrogen oxidation/evolution activity on monometallic platinum.

The Impact of Pt-Nanocluster Deposition and Nafion® Content on the Oxygen Electroreduction Kinetics on Molybdenum Carbide Derived Carbon Synthesized at 1000°C

Molybdenum carbide derived carbon was used as a porous support for platinum catalyst. Platinum was deposited onto carbon support in the form of nanoparticles using NaBH4 reduction method in ethylene glycol, so that the loading of platinum was 8.5 wt% and the average size of platinum nanoparticles was 3 nm. The high resolution scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and the low temperature N2 sorption experiments were applied to characterize the structure of materials prepared. The kinetics of oxygen electroreduction was studied using cyclic voltammetry and rotating disc electrode methods in 0.5 M H2SO4 solution. The content of Nafion® was varied in the range from 5 to 30 wt%. As synthesized carbon exhibited high specific surface area and Nafion® binder disperses uniformly, the percentage of Nafion® has only slight influence on the electrochemical activity. Prepared catalyst materials demonstrated high activity towards oxygen electroreduction.

(Invited) Enhanced Activities for the Oxygen Reduction Reaction at Pt-Skin Layers on Pt-Co Alloy Single-Crystal Electrodes

The kinetically-controlled current densities, j k for the oxygen reduction reaction (ORR) were evaluated at Pt skin layers formed on Pt100−x Co x (111) single-crystal electrodes in air-saturated 0.1 M HClO4 solution as a function of Co content, x atom%, by use of the rotating disk electrode method. We found a maximum j k value as high as 3.0 mA cm−2 at 0.9 V vs. RHE on the Pt skin/Pt75Co25(111) electrode, which is more than 20 times higher than that on the Pt(111) electrode. The enhanced ORR activities of Pt-skin/Pt-Co(111) electrodes cannot be explained on the basis of decreased “OH poisoning,” because the surface oxidation charge densities up to 0.9 V in N2-purged solution were nearly constant, irrespective of Co content.

Mechanism of the effect of oxygen-modified carbon nanotubes on the kinetics of oxygen electroreduction on platinum

The relationship between the concentration of quinone groups in the electrode material containing carbon nanotubes (CNTs) and platinized carbon black and the efficiency of the use of the platinum surface in oxygen reduction was studied by cyclic voltammetry and rotating disc electrode methods. The effect of quinone groups on the oxygen coverage of the platinum surface and the density of the kinetic currents of molecular oxygen reduction on the platinum surface was investigated. A mechanism by which the oxygen-modified CNTs affect the kinetics of oxygen electroreduction on platinum was suggested.

Phosphomolybdate@poly(diallyldimethylammonium chloride)-reduced graphene oxide modified electrode for highly efficient electrocatalytic reduction of bromate

Phosphomolybdate ([PMo12O40]3− or PMo12) was adsorbed onto a poly(diallyldimethylammonium chloride) functionalized reduced graphene oxide (rGO-PDDA) modified glassy carbon electrode (GCE). Compared to monolayer formation of PMo12 on a bare GCE, the rGO-PDDA electrode has a significantly increased loading of PMo12, due to its much larger surface area. The presence of positively charged PDDA also favors the adsorption of negatively charged PMo12 and enhances the stability of the modified electrode. The fabricated electrode (PMo12@rGO-PDDA/GCE) was characterized by scanning electron microscopy as well as energy dispersive X-ray, Raman and FT-IR spectroscopies and applied to the electrocatalytic reduction of bromate. Cyclic voltammetry showed that PMo12@rGO-PDDA/GCE exhibits high electrocatalytic performance and good stability for the reduction of bromate. A wide linear current vs. bromate concentration response (0.02–10mM) was achieved with excellent sensitivity (454μAcm−2mM−1). The kinetics for the electrocatalytic reduction of bromate and the number of electron involved were evaluated using the rotating disk electrode method.

The Application of Novel Electrochemical Approach to Antioxidant Activity Assay of Metal Porphyrins with Bulky 3,5-Diisobornyl-4-hydroxyphenyl Moieties

The complexes of biogenic metals (Zn2+,Cu2+,Co2+,Mn3+,Fe3+) based on meso-tetra(3,5-diisobor- nyl-4-hydroxyphenyl)porphyrin 1 were synthesized. The electrochemical behavior of these com-pounds was studied using cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. The antioxidant activity of complexes was estimated by means of the electrochemical assay based on the hydrogen atom transfer reaction to the stable radical 2,2’-diphenyl-1-picrylhydrazyl (DPPH). The RDE method was applied for this process monitoring. It was shown that the efficiency of the metal complexes (Cu2+,Co2+,Mn2+,Ni2+,Fe3+) is practically the same order as that of free base porphyrin 1. However the Zn2+ complex demonstrates significantly higher antioxidant activity, and the stoichiometry of the reaction was determined as σ = 4. The results demonstrate that porphyrin macrocycle can directly affect the antioxidant properties of 2,6-diisobornylphenol.

Performance of polyaniline-derived Fe-N-C catalysts for oxygen reduction reaction in alkaline electrolyte

Without the presence of any precious metal, Fe-N-C materials derived from pyrolysis of polyaniline (PANI)/carbon/FeCl 3 mixtures are recognized as new catalysts for cathodic oxygen reduction reaction (ORR) in acidic electrolyte. How these Fe-N-C catalysts would perform in an alkaline electrolyte remains yet unknown. Reported here are assessments of the ORR performance of two Fe-N-C catalysts (Fe content: 3.4% and 5.9%) in auqeous KOH by rotating disk electrode methods. Both Fe-N-C catalysts were found much more active than those metal-free N-doped carbon materials in literature. Moreover, the ORR onset and half-wave potentials over both Fe-N-C catalysts were respectively within 60 and 40 mV from those delivered by conventional Pt/C catalyst and both Fe-N-C catalysts even showed much superior catalytic stability in chronoamperometric measurement. ORR on the present Fe-N-C catalysts proceeded predominantly via a four-electron transfer mechanism. This work would shed a light on Fe-N-C materials for ORR catalysis in alkaline fuel cells. The onset and half-wave potentials of PANI-derived Fe-N-C catalysts are found close to conventional Pt/C catalyst for cathodic ORR in alkaline electrolyte; the Fe-N-C catalysts show even significantly higher stabilities.

Effect of thickness of nonplatinum cobalt-tetramethoxyphenylporphyrin-based catalyst layer on the selectivity of O2 electrochemical reduction

Kinetics of O2 reduction at CoPP/XC72-catalyst in acid electrolyte is studied by the rotating disc electrode method. The data obtained with rotating ring-disc electrode over the 1-to-26 μm thickness range showed the effect of the porous layer thickness on the selectivity of O2 reduction reaction. Composition of the catalyst active centers is discussed, their number estimated.

Impact of the Pt catalyst on the oxygen electroreduction reaction kinetics on various carbon supports

Micro- and mesoporous carbide-derived carbons synthesized from molybdenum and tungsten carbides were used as porous supports for a platinum catalyst. Synthesized materials were compared with commercial Vulcan XC72R conducting furnace black. The scanning electron microscopy, X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, and low-temperature N2 adsorption methods were applied to characterize the structure of catalysts prepared. The kinetics of oxygen electroreduction in 0.5 M H2SO4 solution was studied using cyclic voltammetry and rotating disk electrode methods. The synthesized carbide-derived carbons exhibited high specific surface area and narrow pore size distribution. The platinum catalyst was deposited onto the surface of a carbon support in the form of nanoparticles or agglomerates of nanoparticles. Comparison of carbide-derived carbons and Vulcan XC72R as a support showed that the catalysts prepared using carbide-derived carbons are more active towards oxygen electroreduction. It was shown that the structure of the carbon support has a great influence on the activity of the catalyst towards oxygen electroreduction.

Pt–Pd bimetallic nanoparticles on MWCNTs: catalyst for hydrogen peroxide electrosynthesis

Bimetallic nanoparticles of Pt–Pd were deposited by the microemulsion method on a multiwall carbon nanotube (MWCNTs) to obtain a Pt–Pd/MWCNTs for electrocatalytic reduction of O2 to H2O2. The activity and selectivity of the catalyst was determined qualitatively by the rotating disk electrode method in acidic medium. The catalyst was spray-coated onto a reticulated vitreous carbon substrate and quantitatively was tested in bulk electrolysis for 20 min under potentiostatic conditions (0.5 V vs Ag/AgCl) in a 0.5 M H2SO4 electrolyte using dissolved O2. The bulk electrolysis experiments show that the Pt–Pd/MWCNTs catalyst is more efficient for H2O2 electrogeneration than a MWCNTs catalyst. Nitrobenzene degradation by electrogenerated H2O2 alone and Electro-Fenton process were also tested. Our results show that both processes decompose nitrobenzene, but the Electro-Fenton process does it more efficiently. The prepared nanoparticulated catalyst shows a great potential in environmental applications.