TY - CHAP A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae A1 - Brodmann, Michael T1 - Effect of the Process Parameters for Oxygen Plasma Activation of Carbon Nanofibres on the Characteristics of Deposited Platinum Catalyst Nanoparticles T2 - Konferenz: The Annual World Conference on Carbon, 12.-17. Juli 2015 in Dresden N2 - In state of the art polymer electrolyte membrane fuel cells (PEMFC) rare and expensive platinum group metals (PGM) are used as catalyst material. Reduction of PGM in PEMFC electrodes is strongly required to reach cost targets for this technology. An optimal catalyst utilisation is achieved in the case of nano-structured particles supported on carbon material with a large specific surface area. In this study, graphitic material in form of carbon nanofibres (CNFs) is decorated with platinum (Pt) particles serving as catalyst material for PEMFC electrodes with low Pt loading. For electrode preparation CNFs have been previously activated by means of radio frequency induced oxygen plasma. This kind of treatment results in formation of functional groups on the CNF’s surface which directly influences the characteristics of subsequent Pt particle deposition. Different plasma parameters (plasma power, gas flow or exposure time) have to be set in order to achieve formation of oxygen containing functional groups (hydroxylic, carboxylic or carbonylic) on the CNF’s surface. In the frame of this experimental work, electrodes are investigated in respect of optimal morphology, microstructure as well as electrochemical properties. Therefore, samples were characterised by means of scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, thermogravimetry, X-ray diffraction, X-ray fluorescence as well as polarisation measurements. Y1 - 2015 N1 - Die Konferenzbeiträge sind auf einem Datenträger an die Teilnehmer ausgehändigt worden. ER - TY - JOUR A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Marginean, Gabriela A1 - Merino, Cesar A1 - Diez, Roberto A1 - Vaszilcsin, Nicolae A1 - Brodmann, Michael T1 - Effect of Process Parameters for Oxygen Plasma Activation of Carbon Nanofibers on the Characteristics of Deposited Platinum Nanoparticles as Electrocatalyst in Proton Exchange Membrane Fuel Cells JF - International Journal of Electrochemical Science N2 - In the polymer electrolyte membrane fuel cells (PEMFC) state of the art, rare and expensive platinum group metals (PGM) or PGM alloys are used as catalyst material. Reduction of PGMs in PEMFC electrodes is strongly required to reach cost targets for this technology. An optimal catalyst utilization is achieved in case of nano-structured particles supported on carbon material with a large specific surface area. In this study, graphitic material, in form of carbon nanofibers (CNF), is decorated with Pt particles, serving as catalyst material for PEMFC electrodes with low Pt loading. As a novelty, the effect of oxygen plasma treatment of CNFs previously to platinum particle deposition has been studied. Electrodes are investigated in respect of the optimal morphology, microstructure as well as electrochemical properties. Therefore, samples are characterized by means of scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, thermogravimetry, X-ray diffraction as well as X-ray fluorescence analysis. In order to determine the electrochemical active surface area of catalyst particles, cyclic voltammetry has been performed in 0.5 M sulphuric acid. Selected samples have been investigated in a PEMFC test bench according to their polarization behavior. KW - PEM fuel cell electrocatalysts KW - Carbon nanofibers KW - Oxygen plasma activation KW - Pulsed electroplating. Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-9509 SN - 1452-3981 VL - 2016 IS - Volume 11, Issue 11 SP - 9110 EP - 9122 PB - Elsevier ER - TY - JOUR A1 - Muntean, Roxana A1 - Rost, Ulrich A1 - Pascal, Dragos-Toader A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae T1 - Determination of the Electrochemical Surface Area for CNF-Pt Electrocatalyst Using Cyclic Voltammetry JF - Chemical Bulletin of “Politehnica” University of Timisoara, Romania N2 - Carbon Nanofibers (CNF) are considered to be a promising catalyst support material due to their unique characteristics, excellent mechanical, electrical and structural properties, high surface area and nevertheless, good interaction with metallic catalyst particles. The possibility of preparing CNF decorated with platinum by an electrochemical method was tested, using a hexachloroplatinic bath solution. The experiments were carried out with the aid of a Potentiostat/Galvanostat Ivium Technologies Vertex, in a three – electrode cell. The aim of the present work was to determine the electrochemical surface area (ECSA) of the CNF-Pt catalysts in relation to the functionalization treatment of fibers, using an electrochemical method. ECSA for different functionalized CNF-Pt catalysts was determined by cyclic voltammetry in 0.5 M H2SO4 solution. The highest active surface of platinum was obtained for the samples with CNF functionalized by plasma treatment using 80 W for 1800 s. The obtained results correlate very well with the particles size and distribution of platinum, revealed by scanning electron microscopy (SEM) and the quantity of deposited platinum determined by thermo gravimetrical analysis (TGA) respectively. Cyclic voltammetry (CV) has been proven to be a suitable method for estimation of the ECSA of the electrocatalysts. KW - carbon nanofibers KW - platinum electrodeposition KW - electrochemical surface area Y1 - 2016 VL - 61 (75) IS - 2 SP - 44 EP - 48 ER - TY - JOUR A1 - Muntean, Roxana A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae T1 - Optimisation of the Electrodeposition Parameters for Platinum Nanoparticles on Carbon Nanofibers Support JF - Solid state phenomena N2 - Platinum nanoparticles electrodeposition on carbon nanofibers (CNF) support has been performed with the purpose to obtain electrodes that can be further used especially in a polymer electrolyte membrane fuel cell (PEMFC). A pretreatment of CNF is required in order to enhance the surface energy, which simultaneously improves handling and wettability as well as interaction with the platinum cations. This step was performed using oxygen plasma functionalization. To produce CNF supported Pt catalysts, an electrochemical method was applied and the deposition parameters were adjusted to obtain nanosized platinum particles with a good distribution onto the graphitic surface. The morphology and structure of the obtained particles were investigated by scanning electron microscopy combined with energy dispersive X-Ray spectroscopy. The amount of deposited platinum was established using thermogravimetrical measurements. Cyclic voltammetry performed in 0.5 M H2SO4 solution was applied for determining the electrochemical surface area (ECSA) of the obtained electrodes.The functionalization degree of the CNF outer surface has a strong influence on the structure, distribution and amount of platinum particles. Moreover, the current densities, which were set for the deposition process influenced not only the particles size but also the platinum amount. Applying an oxygen plasma treatment of 80 W for 1800 s, the necessary degree of surface functionalization is achieved in order to deposit the catalyst particles. The best electrodes were prepared using a current density of 50 mA cm-2 during the deposition process that leads to a homogenous platinum distribution with particles size under 80 nm and ECSA over 6 cm2 KW - carbon nanofibers KW - platinum electrodeposition KW - electrocatalysts Y1 - 2016 U6 - https://doi.org/10.4028/www.scientific.net/SSP.254.153 IS - 254 SP - 153 EP - 158 ER - TY - CHAP A1 - Muntean, Roxana A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae ED - Transilvania University of Brasov - Romania. Faculty of Materials Science and Engineering, T1 - Determination of the electrochemical surface area for CNTs-PT electro catalyst using cyclic voltammetry T2 - Konferenz: BraMat 2015, 9th International Conference on Materials Science & Engineering, March 5-7, 2015. Book of Abstracts N2 - Platinum is one of the most effective electro catalysts for PEMFCs (proton exchange membrane fuel cells), but because of its prohibitive price, the use of this metal in industrial purposes is limited. As a consequence, during last years, several materials have been investigated, in order to obtain an efficient catalyst for both ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction), which can replace the expensive platinum but preserving the same properties: high electrical conductivity, structural stability and good corrosion resistance. Moreover, one of the most important parameters for catalyst materials is the electrochemical surface area (real surface area), which has a strong influence on the reaction rate and also on the current density. CNFs (carbon nanofibers) are considered to be a promising catalyst support material due to their unique characteristics, excellent mechanical, electrical and structural properties, high surface area and nevertheless, good interaction with platinum particles. The possibility of preparing CNFs decorated with platinum by electrochemical methods was tested, using a hexachloroplatinic solution bath. The experiments were carried out with the aid of a Potentiostat/Galvanostat MMate 510, in a three – electrode cell. The aim of the present work was to determine the electrochemical surface area of the CNFs – Pt catalysts, using an electrochemical method. The obtained results correlate very well with the particles size and distribution of platinum, analyzed by SEM (scanning electron microscopy) respectively with the quantity of deposited platinum determined by TG (thermo gravimetrical analyses). Cyclic voltammetry is a suitable method for estimation of the real surface area for catalyst particles. Y1 - 2015 SP - 170 PB - Transilvania University of Brasov - Romania CY - Brasov ER - TY - CHAP A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae A1 - Brodmann, Michael T1 - PtCoMn ternary alloy supported catalysts for hydrogen evolution reaction T2 - Konferenz: 10th International Conference on Hydrogen Production, 15.-17. Mai 2019 in Cluj-Napoca, Rumänien Y1 - 2019 ER - TY - JOUR A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Vaszilcsin, Nicolae T1 - Synthesis and characterisation of platinum–cobalt–manganese ternary alloy catalysts supported on carbon nanofibers: An alternative catalyst for hydrogen evolution reaction JF - International Journal of Hydrogen Energy N2 - A systematic method for obtaining a novel electrode structure based on PtCoMn ternary alloy catalyst supported on graphitic carbon nanofibers (CNF) for hydrogen evolution reaction (HER) in acidic media is proposed. Ternary alloy nanoparticles (Co0.6Mn0.4 Pt), with a mean crystallite diameter under 10 nm, were electrodeposited onto a graphitic support material using a two-step pulsed deposition technique. Initially, a surface functionalisation of the carbon nanofibers is performed with the aid of oxygen plasma. Subsequently, a short galvanostatic pulse electrodeposition technique is applied. It has been demonstrated that, if pulsing current is employed, compositionally controlled PtCoMn catalysts can be achieved. Variations of metal concentration ratios in the electrolyte and main deposition parameters, such as current density and pulse shape, led to electrodes with relevant catalytic activity towards HER. The samples were further characterised using several physico-chemical methods to reveal their morphology, structure, chemical and electrochemical properties. X-ray diffraction confirms the PtCoMn alloy formation on the graphitic support and energy dispersive X-ray spectroscopy highlights the presence of the three metallic components from the alloy structure. The preliminary tests regarding the electrocatalytic activity of the developed electrodes display promising results compared to commercial Pt/C catalysts. The PtCoMn/CNF electrode exhibits a decrease in hydrogen evolution overpotential of about 250 mV at 40 mA cm−2 in acidic solution (0.5 M H2SO4) when compared to similar platinum based electrodes (Pt/CNF) and a Tafel slope of around 120 mV dec−1, indicating that HER takes place under the Volmer-Heyrovsky mechanism. KW - PtCoMn KW - Ternary alloy catalyst preparation KW - PEM water electrolysis KW - Hydrogen evolution reaction Y1 - 2020 U6 - https://doi.org/10.1016/j.ijhydene.2020.02.041 SN - 0360-3199 ER - TY - JOUR A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Vaszilcsin, Nicolae T1 - Synthesis and characterisation of platinum–cobalt–manganese ternary alloy catalysts supported on carbon nanofibers: An alternative catalyst for hydrogen evolution reaction JF - International Journal of Hydrogen Energy Y1 - 2020 U6 - https://doi.org/10.1016/j.ijhydene.2020.02.041 VL - 45 IS - 49 SP - 26217 EP - 26225 ER - TY - JOUR A1 - Kellenberger, Andrea A1 - Vaszilcsin, Nicolae A1 - Duca, Delia A1 - Dan, Mircea Laurentiu A1 - Duteanu, Narcis A1 - Stiber, Svenja A1 - Morawietz, Tobias A1 - Biswas, Indro A1 - Ansar, Syed Asif A1 - Gazdzicki, Pawel A1 - Wirkert, Florian Josef A1 - Roth, Jeffrey A1 - Rost, Ulrich A1 - Brodmann, Michael A1 - Saul Gago, Aldo A1 - Friedrich, Kaspar Andreas T1 - Towards Replacing Titanium with Copper in the Bipolar Plates for Proton Exchange Membrane Water Electrolysis JF - Materials 2022, 15(5), 1628 N2 - For proton exchange membrane water electrolysis (PEMWE) to become competitive, the cost of stack components, such as bipolar plates (BPP), needs to be reduced. This can be achieved by using coated low-cost materials, such as copper as alternative to titanium. Herein we report on highly corrosion-resistant copper BPP coated with niobium. All investigated samples showed excellent corrosion resistance properties, with corrosion currents lower than 0.1 µA cm−2 in a simulated PEM electrolyzer environment at two different pH values. The physico-chemical properties of the Nb coatings are thoroughly characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). A 30 µm thick Nb coating fully protects the Cu against corrosion due to the formation of a passive oxide layer on its surface, predominantly composed of Nb2O5. The thickness of the passive oxide layer determined by both EIS and XPS is in the range of 10 nm. The results reported here demonstrate the effectiveness of Nb for protecting Cu against corrosion, opening the possibility to use it for the manufacturing of BPP for PEMWE. The latter was confirmed by its successful implementation in a single cell PEMWE based on hydraulic compression technology. KW - PEMWE KW - water electrolysis KW - bipolar plate KW - corrosion resistance KW - coatings Y1 - 2022 U6 - https://doi.org/10.3390/ma15051628 N1 - This article belongs to the Special Issue Recent Research on Energy Storage Materials: Properties and Applications. ER -