MTA SZTE Lendulet Photoelectrochemistry Research Group

Szeged, Hungary

MTA SZTE Lendulet Photoelectrochemistry Research Group

Szeged, Hungary

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Samu G.F.,University of Szeged | Samu G.F.,MTA SZTE lendulet Photoelectrochemistry Research Group | Visy C.,University of Szeged | Rajeshwar K.,University of Texas at Arlington | And 4 more authors.
Electrochimica Acta | Year: 2014

Photoelectrochemical synthesis of TiO2/CdX/PEDOT [X: S, Se; PEDOT = poly(3,4-ethylenedioxythiophene)] ternary hybrids was carried out by exploiting the semiconductor (SC) nature of both the oxide and the chalcogenide component. To this end, TiO2 nanotube arrays were initially electrosynthesized on titanium foils by anodization in fluoride-containing aqueous media. CdS and CdSe quantum dots were subsequently deposited on the nanotubes using successive ionic layer adsorption and reaction (SILAR). The conjugated polymer, PEDOT, was then grafted using photoelectrochemical excitation of the SC matrix and potentiodynamic deposition, to ultimately afford the ternary hybrid architecture. The morphology, structural properties, and chemical composition of these assemblies were evaluated by scanning electron microscopy, diffuse reflectance UV-Vis spectrophotometry, and Raman spectroscopy, while their electroactivity was evaluated by cyclic voltammetry. Photoelectrochemical deposition of the conducting polymer was carried out both through selective excitation of the chalcogenide sensitizer and the collective photoexcitation of the two SC components. Two precursor molecules, namely, EDOT or bis-EDOT were compared and contrasted in terms of their relative proclivity to oligomer/polymer formation. The use of UV or visible spectral wavelength components allowed for discrimination between the various polymer formation and SC photoexcitation pathways.

Endrodi B.,University of Szeged | Endrodi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Samu G.F.,University of Szeged | Samu G.F.,MTA SZTE Lendulet Photoelectrochemistry Research Group | And 4 more authors.
Journal of Solid State Electrochemistry | Year: 2016

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. [Figure not available: see fulltext.] © 2016 Springer-Verlag Berlin Heidelberg

Janaky C.,University of Szeged | Janaky C.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Rajeshwar K.,University of Texas at Arlington
Progress in Polymer Science | Year: 2015

Abstract Hybrid materials based on conducting polymers (CPs) and inorganic semiconductors (SCs) undoubtedly constitute one of the most promising classes of new materials. The spectacular progress in this research topic has been driven by the development of novel synthetic procedures and by the large variety of applications. Beyond scientific and fundamental interest, such hybrid assemblies are attractive from technological perspectives as well, for example, in energy conversion and storage, electronics, catalysis, and optics. This article is designed to be a critical overview for the polymer materials science community on how to employ electrosynthetic methods to obtain hybrid materials with well-designed composition and morphology. As this review illustrates, (photo)electrochemical approaches are versatile and powerful tools in the preparation of conjugated polymer-based composites, containing both elemental and compound semiconductors. Hybridization of CPs with metal oxides (TiO2, WO3, ZnO, NiO, Cu2O, CuO, V2O5, Fe2O3, Fe3O4, MnO2, SnO2, RuO2), metal chalcogenides (CdS, CdTe, CdSe, Bi2S3), and carbon nanomaterials (nanotubes, graphene, graphene oxide) is presented. We demonstrate that both composition and nanoscale architecture of the hybrid assemblies can be precisely controlled by employing carefully designed electrochemical methods. To achieve the goal of popularizing electro- and photoelectrosynthetic procedures, particular attention will be paid to compare the as-synthesized assemblies with their counterparts obtained from other procedures. The most prominent applications of these electrosynthesized materials are highlighted, with particular focus on energy related utilization pathways. © 2014 Elsevier Ltd. All rights reserved.

Samu G.F.,University of Szeged | Samu G.F.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Pencz K.,University of Szeged | Janaky C.,University of Szeged | And 2 more authors.
Journal of Solid State Electrochemistry | Year: 2015

The aim of this study is to tailor the electrochemical synthesis of hybrid materials consisting of nanoporous tungsten trioxide (WO3) and polyaniline (PANI) for application as supercapacitor electrodes. Nanoporous WO3, synthesized by the anodization of tungsten foils, acted as the active material framework for this assembly. With the variation of the anodization voltage, host materials with different morphological features were prepared. Subsequently, electrodeposition of PANI was carried out by potentiodynamic cycling in highly acidic media. Through alteration of the number of deposition cycles, the amount of deposited PANI was varied. This parameter had a decisive impact on the morphology of the resulting hybrids as confirmed by SEM images. Cyclic voltammetry and galvanostatic charge–discharge measurements were carried out to characterize the charge storage properties of the synthesized hybrids. By comparing electrochemical data with structural properties, structure–property relationships were established, and under optimal conditions, 350 F g−1 and 200 mF cm−2 were obtained. © 2015, Springer-Verlag Berlin Heidelberg.

Kecsenovity E.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Kecsenovity E.,University of Szeged | Endrodi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Endrodi B.,University of Szeged | And 5 more authors.
Journal of Materials Chemistry A | Year: 2016

Photoelectrochemical reduction of CO2 to form useful chemicals is an increasingly studied avenue for harnessing and storing solar energy. In the quest for efficient and stable photocathode materials, nanostructured hybrid assemblies are eminently attractive candidates, because they exhibit multiple favorable properties that cannot be expected from a single material. One possible direction is to combine p-type inorganic semiconductors with highly conductive large surface area electrodes such as carbon nanotube networks. In this work, the controlled synthesis and photoelectrochemical behavior of CNT/Cu2O films was reported for the first time for CO2 reduction applications. A carefully designed, multiple-step electrodeposition protocol was developed that ensured homogeneous coating of CNTs with Cu2O nanocrystals. The hybrid materials were characterized by electron microscopy, X-ray diffraction, Raman spectroscopy, electrochemical impedance spectroscopy, and photoelectrochemical methods. The hybrid films had five-fold higher electrical conductivity compared to their pure Cu2O counterparts. This enhanced charge transport property resulted in a drastic increase in the photocurrents measured for CO2 reduction. In addition to this superior performance, long term photoelectrolysis measurements proved that the CNT/Cu2O hybrids were more stable than the oxide alone. These observations, together with the established structure/property relationships, may contribute to the rational design of nanocarbon/inorganic semiconductor hybrid photocathodes for deployment in photoelectrochemical cells. © 2016 The Royal Society of Chemistry.

Hursan D.,University of Szeged | Hursan D.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Kormanyos A.,University of Szeged | Kormanyos A.,MTA SZTE Lendulet Photoelectrochemistry Research Group | And 4 more authors.
Chemical Communications | Year: 2016

In this communication, we demonstrate that polyaniline, the very first example of an organic semiconductor, is a promising photocathode material for the conversion of carbon dioxide (CO2) to alcohol fuels. CO2 is a greenhouse gas; thus using solar energy to convert CO2 to transportation fuels (such as methanol or ethanol) is a value-added approach to simultaneous generation of alternative fuels and environmental remediation of carbon emissions. Insights into its unique behavior obtained from photoelectrochemical measurements and adsorption studies, together with spectroscopic data, are presented. Through a comparative study involving various conducting polymers, a set of criteria is developed for an organic semiconductor to function as a photocathode for generation of solar fuels from CO2. © The Royal Society of Chemistry 2016.

Endrodi B.,University of Szeged | Endrodi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Mellar J.,University of Szeged | Gingl Z.,University of Szeged | And 3 more authors.
Journal of Physical Chemistry C | Year: 2015

In this study, we investigated the impact of molecular and supramolecular structure of conducting polymers (CPs) on their thermoelectric properties. As a model system, poly(3-alkylthiophene)s (P3ATs) with different side-chain lengths were prepared through oxidative chemical polymerization and were recrystallized to a well-ordered lamellar structure, resulting in one-dimensional self-assembled nanofibers (evidenced by transmission electron microscopy, X-ray diffraction, and UV-vis spectroscopic measurements). Thermoelectric characterization was performed at different doping levels (precisely tuned by doping in the redox reaction with Ag+ and Fe3+ cations), and the highly doped samples exhibited the best performance for all studied polymers. By varying the length of the alkyl side chain, the supramolecular structure and consequently the electronic properties were varied. The highest electrical conductivity was measured for poly(3-butylthiophene), rooted in its densely packed structure. The established structure-property relationships, concerning the monotonous decrease of the electrical conductivity with the alkyl side chain length, highlight the importance of the supramolecular structure (interchain distance in this case). These findings may contribute to the rational design of organic thermoelectric materials. © 2015 American Chemical Society.

Hursan D.,University of Szeged | Hursan D.,MTA SZTE Lendulet Photoelectrochemistry Research Group | London G.,University of Szeged | Olasz B.,University of Szeged | And 3 more authors.
Electrochimica Acta | Year: 2016

A newly designed conducting polymer (poly(N(-pyridin-4-ylmethyl)aniline)), POB), having a polyaniline backbone and pyridine pendant groups, has been electrosynthesized and studied in this paper. The characterization predominantly focuses on the possible application of the polymer-modified electrode in electrochemical fuel generation (H2 production and CO2 reduction). POB can be regarded as a pyridine-based electrocatalyst (mediator) immobilized on an electrode surface as part of a conjugated polymer, as confirmed by the appearance of a redox wave centered at E = −0.53 V (vs. Ag/AgCl) on the cyclic voltammogram of POB. The effects of experimental conditions (pH of the electrolyte, layer thickness, and material of the substrate electrode) on the immobilized pyridine-ring electrochemistry have been carefully analyzed, to understand the underlying factors governing the electrochemical behavior of this new functional material. Finally, the electrocatalytic behavior of POB was tested towards CO2 reduction and H2 evolution. © 2016 Elsevier Ltd

Toth P.S.,University of Szeged | Endrodi B.,University of Szeged | Endrodi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Janaky C.,University of Szeged | And 2 more authors.
Journal of Solid State Electrochemistry | Year: 2015

Investigation of ionic motion in connection with the redox transformation of conjugated polymers (CP) has always been at the leading edge of research. Motivated by recent proofs for the chemical bond formation between chloride ion and α-positioned carbon in poly (3,4–ethylenedioxythiophene) (PEDOT), comprehensive studies have been extended to another strongly electronegative halide (F−) and to another CP, polypyrrole (PPy). As the electrochemical quartz crystal nanobalance (EQCN) results proved, the movement of the bulky Bu4N+ cations has been exclusively experienced during the redox processes of both systems. Moreover, the decisive role of the anions being present in the polymerization solution in determining the redox capacity and, consequently, the maximum doping level of the films was evidenced. On the grounds of the systematic experiments, the strong and permanent chemical interaction of highly electronegative anions and the polymer has been demonstrated as a general phenomenon. Importantly, this observation requires the necessary reconsideration of specific polymer–dopant interactions and calls attention to the necessity of careful design of the polymerization procedure. © 2015, Springer-Verlag Berlin Heidelberg.

Endrdi B.,University of Szeged | Endrdi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Mellar J.,University of Szeged | Gingl Z.,University of Szeged | And 3 more authors.
RSC Advances | Year: 2014

Enhanced thermoelectric properties of poly(3-hexylthiophene) nanofiber networks, doped in their reaction with silver cations, are presented. The role of charge carrier concentration and mobility (influenced by the supramolecular structure and nanoscale morphology) is discussed. The nanonet structure leads to a six fold increase in the ZT value compared to the bulk polymer counterpart. This journal is © 2014 The Royal Society of Chemistry.

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