MTA SZTE Lendulet Photoelectrochemistry Research Group

Szeged, Hungary

MTA SZTE Lendulet Photoelectrochemistry Research Group

Szeged, Hungary
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Endrodi B.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Endrodi B.,University of Szeged | Bencsik G.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Bencsik G.,University of Szeged | And 5 more authors.
Progress in Energy and Combustion Science | Year: 2017

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 CO2 electrolyzers. Finally, we give a brief outlook on photoelectrochemical reactors where solar energy input is directly utilized. © 2017

Samu G.F.,University of Szeged | Samu G.F.,MTA SZTE Lendulet Photoelectrochemistry Research Group | Samu G.F.,University of Texas at Arlington | Veres A.,University of Szeged | And 7 more authors.
Applied Catalysis B: Environmental | Year: 2017

Ternary and quaternary metal oxides form a rapidly emerging class of new functional materials tackling the grand challenge of efficient solar energy harvesting. Currently the main interest is devoted to the characteristics of these materials and little consideration has been given to their preparation. Solution combustion synthesis (SCS) is considered a green and sustainable alternative to the widely employed energy- and/or time-consuming synthesis methods. In this study, SCS was employed to prepare Bi2Ti2O7 and to perform bandgap engineering through foreign ion (Fe, Mn) incorporation. The synthesized materials were characterized by powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray microanalysis, diffuse reflectance UV–vis and Raman spectroscopy, and surface area determination via N2 adsorption. We found that nanocrystalline materials were formed during the SCS synthesis. Further, the phase composition of these materials and the amount of the foreign metal ions incorporated in the parent structure, could be effectively controlled. Consequently, the SCS technique provided a simple and reliable tool for bandgap engineering. The photocatalytic activity of the materials was tested through methyl orange degradation, and the intrinsic photocatalytic activity of the various samples were compared after deconvoluting the effect of their vastly different specific surface areas. © 2017 Elsevier B.V.

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.

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

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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