| 1. |
- Bencsik, G., et al.
(författare)
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Conducting polymer based multifunctional composite electrodes
- 2009
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Ingår i: Reaction Kinetics and Catalysis Letters. - : Springer. - 0133-1736 .- 1588-2837. ; 96, s. 421-428
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report a novel pattern of composite electrocatalysts. PPy/iron-oxalate films exhibit photo-electrochemical activity. The PPy/B12 composite electrode on stainless steal (SS) support shows high catalytic activity in the electrochemical reduction of methylviologen. Thin polymer layers filled with magnetite particles can be applicable in magneto-selective electrochemical reactions.In this paper, we report a novel pattern of composite electrocatalysts. PPy/iron-oxalate films exhibit photo-electrochemical activity. The PPy/B12 composite electrode on stainless steal (SS) support shows high catalytic activity in the electrochemical reduction of methylviologen. Thin polymer layers filled with magnetite particles can be applicable in magneto-selective electrochemical reactions.
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| 2. |
- Bencsik, Gábor, et al.
(författare)
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Electrocatalytic properties of the polypyrrole/magnetite hybrid modified electrode towards the reduction of hydrogen peroxide in the presence of dissolved oxygen
- 2012
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 73, s. 53-58
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report on the electrocatalytic behaviour of a polypyrrole/magnetite hybrid electrode towards the reduction of hydrogen peroxide. The electrocatalytic activity of the composite electrode was demonstrated by cyclic voltammetric and chrono-amperometric measurements in comparison with the identically prepared neat polymer film. The stationary reduction currents, measured at an appropriately chosen potential (here at E = -0.3 V), plotted against the peroxide concentration gave a perfect linear correlation in nitrogen atmosphere in the micromolar concentration range. The performance of the composite electrode was not affected by the presence of sulphate, nitrate or chloride anions. In the presence of dissolved oxygen a complex electrocatalytic activity was observed, involving the reduction of both oxygen and H2O2. However, a linear dependence was found also in oxygen containing media, although with much higher currents, but with the same slope (even at different oxygen concentrations). This fact may trigger the development of such hybrid electrodes towards hydrogen peroxide sensors in different aqueous (including natural) samples.
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| 3. |
- Bohner, B., et al.
(författare)
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Flow-driven pattern formation in the calcium-oxalate system
- 2016
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 144
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Tidskriftsartikel (refereegranskat)abstract
- The precipitation reaction of calcium oxalate is studied experimentally in the presence of spatial gradients by controlled flow of calcium into oxalate solution. The density difference between the reactants leads to strong convection in the form of a gravity current that drives the spatiotemporal pattern formation. The phase diagram of the system is constructed, the evolving precipitate patterns are analyzed and quantitatively characterized by their diameters and the average height of the gravity flow. The compact structures of calcium oxalate monohydrate produced at low flow rates are replaced by the thermodynamically unstable calcium oxalate dihydrate favored in the presence of a strong gravity current.
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| 4. |
- Endrodi, Balazs, et al.
(författare)
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A review of chromium(VI) use in chlorate electrolysis : Functions, challenges and suggested alternatives
- 2017
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Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 234, s. 108-122
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Forskningsöversikt (refereegranskat)abstract
- Sodium chlorate is industrially produced by electrolysis of an aqueous salt solution, in which chromium ( VI) constitutes an important excipient component. It is added to a concentration of a few grams Na2Cr2O7/ liter to the electrolyte and has several functions in the process, the most important being to increase the Faradaic efficiency for hydrogen evolution in the undivided electrochemical cells. A thin film of Cr(OH)(3) x nH(2)O formed by reductive deposition on the cathodes decreases the rate of unwanted side reactions, while still enabling hydrogen evolution to occur. In addition chromium(VI) buffers the electrolyte at the optimum pH for operation and promotes the desired homogeneous reactions in the electrolyte bulk. Chromium species also affect the rates of hydrogen and oxygen evolution at the electrodes and are said to protect the steel cathodes from corrosion. Although chromium(VI) stays in a closed loop during chlorate production, chromate is a highly toxic compound and new REACH legislation therefore intends to phase out its use in Europe from 2017. A production without chromium(VI), with no other process modifications is not possible, and today there are no commercially available alternatives to its addition. Thus, there is an urgent need for European chlorate producers to find solutions to this problem. It is expected that chromium-free production will be a requirement also in other parts of the world, following the European example. As the chromium(VI) addition affects the chlorate process in many ways its replacement might require a combination of solutions targeting each function separately. The aim of this paper is to explain the role and importance of chromium(VI) in the chlorate manufacturing process. Previous achievements in its replacement are summarized and critically evaluated to expose the current state of the field, and to highlight the most promising avenues to be followed. An attempt is also made to reveal connections with other research fields (e.g. photochemical water splitting, corrosion science) facing similar problems. Allied effort of these different communities is expected to open up research avenues to the mutual benefit of these fields.
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| 5. |
- Endrődi, Balázs, 1987-, et al.
(författare)
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Challenges and rewards of the electrosynthesis of macroscopic aligned carbon nanotube array/conducting polymer hybrid assemblies
- 2015
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Ingår i: Journal of Polymer Science Part B. - : Wiley. - 0887-6266 .- 1099-0488. ; 53, s. 1507-1518
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid assemblies based on conducting polymers and carbon nanomaterials with organized nanoscale structure are excellent candidates for various application schemes ranging from thermal management to electrochemical energy conversion and storage. In the case of macroscopic samples, however, precise control of the nanoscale structure has remained a major challenge to be solved for the scientific community. In this study we demonstrate possible routes to homogeneously infiltrate poly(3-hexylthiophene), poly(3,4-ethylenedioxythiophene), and polyaniline into macroscopic arrays of vertically aligned multiwalled carbon nanotubes (MWCNTAs). Electron microscopic images and Raman spectroscopic analysis (performed along the longitudinal dimension of the hybrid samples) both confirmed that optimization of the electropolymerization circumstances allowed fine tuning of the hybrid structure towards the targeted application. In this vein, three different application avenues were tested. The remarkable anisotropy in both the electrical and thermal conductivity of the nanocomposites makes them eminently attractive candidates to be deployed in thermal management. Thermoelectric studies, aimed to understand the effect of organized nanoscale morphology on the important parameters (Seebeck coefficient, electrical-, and thermal conductivity) compared to their non-organized hybrid counterparts. Finally, extraordinary high charge storage capacity values were registered for the MWCNTA/PANI hybrids (500 F g−1 and 1–3 F cm−2).
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| 6. |
- Endrodi, Balazs, et al.
(författare)
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Continuous-flow electroreduction of carbon dioxide
- 2017
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Ingår i: Progress in Energy and Combustion Science. - : Elsevier. - 0360-1285 .- 1873-216X. ; 62, s. 133-154
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Tidskriftsartikel (refereegranskat)abstract
- Solar fuel generation through electrochemical CO2 conversion offers an attractive avenue to store the energy of sunlight in the form of chemical bonds, with the simultaneous remediation of a greenhouse gas. While impressive progress has been achieved in developing novel nanostructured catalysts and understanding the mechanistic details of this process, limited knowledge has been gathered on continuous-flow electrochemical reactors for CO2 electroreduction. This is indeed surprising considering that this might be the only way to scale-up this fledgling technology for future industrial application. In this review article, we discuss the parameters that influence the performance of flow CO2 electrolyzers. This analysis spans the overall design of the electrochemical cell (microfluidic or membrane-based), the employed materials (catalyst, support, etc.), and the operational conditions (electrolyte, pressure, temperature, etc.). We highlight R&D avenues offering particularly promising development opportunities together with the intrinsic limitations of the different approaches. By collecting the most relevant characterization methods (together with the relevant descriptive parameters), we also present an assessment framework for benchmarking CO2electrolyzers. Finally, we give a brief outlook on photoelectrochemical reactors where solar energy input is directly utilized.
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| 7. |
- Endrődi, Balázs, 1987-, et al.
(författare)
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Electrochemical synthesis and characterization of poly(3-hexylthiophene)/single-walled carbon nanotube array hybrid materials
- 2016
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Ingår i: Journal of Solid State Electrochemistry. - : Springer. - 1432-8488 .- 1433-0768. ; 20:11, s. 3179-3187
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we demonstrate that by directly employing single-walled carbon nanotube arrays (SWCNT-arrays)-grown on conductive substrates-as working electrodes, selective and uniform electrodeposition of a conducting polymer, namely poly(3-hexylthiophene), can be achieved on the surface of the nanotubes. The overall kinetic pattern of the electrodeposition was studied by separating the deposition charge from the one related to the redox transformation of the polymer film deposited during the precedent cycles. Both the structure and the electrochemical properties of the hybrid materials were studied as a function of the electrodeposition cycles, thus the amount of the formed polymer. The hybrids were characterized by electron microscopic (SEM, TEM) and vibrational spectroscopic (Raman spectroscopy) means. The obtained results were compared and contrasted with those gathered on macroscopic-sized multi-walled carbon nanotube array-based composites in our group recently. Overall, we conclude that electrochemical polymerization is an attractive tool to synthesize conducting polymer/SWCNT hybrid materials with controlled composition and morphology.
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| 8. |
- Endrődi, Balázs, 1987-, et al.
(författare)
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Fixation of laccase enzyme into polypyrrole, assisted by chemical interaction with modified magnetite nanoparticles : A facile route to synthesize stable electroactive bionanocomposite catalysts
- 2014
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 122, s. 282-288
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Tidskriftsartikel (refereegranskat)abstract
- Effective bio-electrocatalysts require stable immobilization of sufficient amounts of the bioactive component. In this study, a novel and efficient method for specific binding of laccase enzyme onto magnetite nanoparticles (NPs) is presented. The interaction between the chemically modified magnetite NPs and the enzyme was evidenced by both infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Subsequently, the enzyme-coated magnetite NPs were successfully incorporated into polypyrrole (PPy) matrix during galvanostatic electropolymerization. The encapsulation of laccase covered NPs was proved by EQCN, TEM, and FT-IR spectroscopy; whereas the electrochemical behaviour of the formed bionanocomposite was characterized by cyclic voltammetiy. In oxygen saturated solution a cathodic charge surplus was observed, related to the electrochemical reduction of oxygen. This surplus was two times higher in the case of the laccase containing layer compared to its only magnetite containing counterpart. Kinetic aspects of the oxygen reduction reaction (ORR) on the laccase containing films were investigated by hydrodynamic voltammetry, and the four-electron route was found to be exclusive, which is promising from the fuel cell perspective. Such synergistic combination of inorganic NPs and enzymes may open new avenues in the application of these bio-nanocomposite materials.
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| 9. |
- Endrodi, Balazs, et al.
(författare)
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In situ formed vanadium-oxide cathode coatings for selective hydrogen production
- 2019
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Ingår i: Applied Catalysis B. - : Elsevier. - 0926-3373 .- 1873-3883. ; 244, s. 233-239
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Tidskriftsartikel (refereegranskat)abstract
- Electrode selectivity towards hydrogen production is essential in various conversion technologies for renewable energy, as well as in different industrial processes, such as the electrochemical production of sodium chlorate. In this study we present sodium metavanadate as a solution additive, inducing selective cathodic formation of hydrogen in the presence of various other reducible species such as hypochlorite, chlorate, oxygen, nitrate, hydrogen-peroxide and ferricyanide. During electrolysis a vanadium-oxide coating forms from the reduction of sodium metavanadate, explaining the observed enhanced selectivity. The hydrogen evolution reaction proceeds without significantly altered kinetics on such in situ modified electrode surfaces. This suggests that the reaction takes place at the interface between the electrode surface and the protective film, which acts as a diffusion barrier preventing the unwanted species to reach the electrode surface.
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| 10. |
- Endrodi, Balazs, et al.
(författare)
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Incorporation of cobalt-ferrite nanoparticles into a conducting polymer in aqueous micellar medium : Strategy to get photocatalytic composites
- 2014
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Ingår i: Acta Chimica Slovenica. - 1318-0207. ; 61, s. 376-381
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Tidskriftsartikel (refereegranskat)abstract
- In this study an easy strategy for conducting polymer based nanocomposite formation is presented through the deposition of cobalt-ferrite (CoFe 2O4) containing poly(3,4-ethylenedioxythiophene) (PEDOT) thin layers. The electrochemical polymerization has been performed galvanostatically in an aqueous micellar medium in the presence of the nanoparticlesand the surface active Triton X-100. The nanoparticles have been characterized by Transmission electron microscopy (TEM), the thin layers has been studied by applying Scanning electron microscopy (SEM), and X-ray diffraction (XRD), and the basic electrochemical properties have been also determined. Moreover, electrocatalytic activity of the composite was demonstrated in the electrooxidation reaction of dopamine (DA). The enhanced sensitivity - related to the cobalt-ferritecontent - and the experienced photocatalyitic activity are promising for future application.
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