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ABSTRACT: The paper presents dc measurements of proton exchange membranes (PEMs) as an integral part of a membrane electrode assembly (MEA) performed in a novel EasyTest Cell testing device. Depending on their operating temperature PEMs are divided in two groups. The commercial Nafion membranes (Alfa Aesar) as well as the self-prepared interpenetrating network of poly(acrylamidepropylsulfonic acid) and poly(acrylamide) (PAMPS–PAM), and Nafion 117 with grafted PAMPS chains (Nafion graft-PAMPS) are tested in the low temperature range (upto 80 °C). The PEMs from the second group (prepared in the frame of EU project AUTOBRANE, FP 6) – phosphoric acid doped polybenzimidazole (PBI/PA) and PBI, containing cross-linked poly(vinylphosphonic acid) (CR-PVPhA) – are investigated for high temperature applications (120–200 °C). The EasyTest Cell is a three electrode electrochemical test that offers the possibility to obtain steady state polarization curves at strict self-regulated constant hydrogen and water vapor partial pressures. The initial slope of the polarization curves, corrected by the electronic resistance of the electrodes under study is used as a criterion for the proton conductivity of the investigated PEMs. The results obtained for the commercially available Nafion are in a good agreement with the available literature data. The PAMPS grafting from Nafion 117 results in 1.5 fold higher proton conductivity compared to the non-grafted one. The proton conductivity of the PBI/PA membrane is almost independent on the relative humidity (RH) in the range of 15–40% (0.110–0.117 S cm−1 at 180 °C) which makes the water management redundant, this way facilitating the fuel cell management. The proton conductivity of the PBI/CR–PVPhA membrane is in the range of 7 × 10−3 S cm−1 (170 °C, 20% RH). The EasyTest Cell working principle and single chamber design allows precise control of vital working parameters (temperature and RH) for the proton conductivity of PEM.
International Journal of Hydrogen Energy.
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ABSTRACT: Thin films of iridium oxide deposited by reactive magnetron sputtering have been investigated as catalysts for electrochemical water splitting in a polymer electrolyte membrane (PEM) cell. The sputtered films possess excellent mechanical stability and corrosion resistance at the high anodic potentials where oxygen evolution takes place. Their catalytic activity has been assessed using the conventional electrochemical methods of cyclovoltammetry and steady state polarisation techniques. A morphology factor assessing the catalyst active surface for a series of sputtered samples with varying thickness/loading has been determined and correlated to the catalytic efficiency. It has been proven that iridium oxide is a very efficient catalyst for oxygen evolution reaction (OER). The best performance with anodic current density of 0.3 A cm−2 at potential of 1.55 V (versus RHE) has shown the 500 nm thick film containing 0.2 mg cm−2 catalyst. The results obtained have also demonstrated the advantages of the reactive magnetron sputtering as simple and reliable method for deposition of efficient and cost effective catalysts for PEM electrolysis application.
Electrochimica Acta.
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ABSTRACT: The paper presents the experimental validation of the “EasyTest Cell” operational principle via comparative electrochemical tests on MEAs carried out in three types of electrochemical hydrogen energy conversion (EHEC) testing cells: conventional polymer electrolyte membrane fuel cells (PEMFC) and polymer electrolyte membrane water electrolyzers (PEMWE), properly equipped with all the required auxiliaries (products conditioning and supplying, reagents removal, etc.), and the simple, autonomous EasyTest Cell. Along with EasyTest Cell validation and demonstration of its advantages, the influence of argon pressure during sputtering on the electrode characteristics, including gas diffusion limitations was investigated. The electrodes under investigation were magnetron sputtered C/Ti/IrOx (IrOx loading in the range 0.12–0.4 mg cm−2), C/Ti/IrOx/Pt/IrOx (IrOx 0.08/Pt 0.06/IrOx 0.08 mg cm−2), sputtered at various argon pressure C/Ti/Pt (0.15 and 0.25 mg cm−2), and commercial ELAT electrode (V.21, Lot # MB030105-1, Pt loading 0.5 mg cm−2, E-TEK). The results obtained proved the reliability, simplicity (running-periphery-free) and broadened experimental possibilities of EasyTest Cell over PEMFC and PEMWE single cell testing. Thus, significant cost reduction and resource saving in R&D laboratory can be achieved. Moreover, validation of EasyTest Cell contributes not only to testing facilitations, but potentially to standardization of MEA testing since it gives possibilities for precise control and more uniform distribution of the working parameters applied to the testing object, which are both compulsory for performance comparison and qualifying.
International Journal of Hydrogen Energy 35(6):2428-2435. · 4.05 Impact Factor
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ABSTRACT: The paper describes an EasyTest cell developed for simple, safe and inexpensive to run testing and optimisation of the active materials (catalysts, catalytic supports, polymer membrane electrolytes) and electrode structures utilized in PEM Fuel cells and Electrolysers. The main advantages of the new EasyTest technique are demonstrated by a comparative study on the performance of two types of membrane electrode assemblies for electrochemical energy conversion. Nafion and PBI-based polymer electrolyte membranes covered with catalytic layers containing 20 % Pt dispersed on carbon black (E-TEK, De Nora) are tested as hydrogen electrodes working in a fuel cell and an electrolyser mode at two characteristic temperatures, varying the total partial pressure in the cell. The PBI-based membrane electrode assembly (MEA) gives lower current densities compared to that containing Nafion, while its performance remains stable in a much broader potential range. At overpotentials of about = 300–350 mV the Nafion MEA reaches a limiting current density, while in the case of PBI-based MEA such an effect is not registered in the whole potential range tested.
Chemical & Biochemical Engineering Quarterly (cabeq@pbf.hr); Vol.21 No.1.
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ABSTRACT: An EasyTest Cell concept is applied to study the performance characteristics of the electrochemical processor for polymer electrolyte membrane electrochemical hydrogen energy converters (PEM EHEC), broadly known as a membrane electrode assembly (MEA). A series of MEAs consisting of Nafion 117 polymer electrolyte and magnetron sputtered Pt, IrOx, and composite IrOx/Pt/IrOx catalysts with varying catalytic loadings were investigated. The partial electrode reactions proceeding in the real PEM EHEC, namely hydrogen oxidation (HOR), hydrogen evolution (HER), oxygen reduction (ORR), and oxygen evolution (OER), are simulated and studied in a recently developed test cell with a unitized gas compartment. The EasyTest Cell design gives possibilities for strict control of the experimental conditions by avoiding the usage of any auxilliary gas conditioning equipment. By varying the thickness of the sputtered Pt film, the catalyst loading is remarkably reduced (from 0.5 to 0.06 mg cm−2 or about 8 times) for both HOR and HER without any sacrifice of the electrode performance. The electrode with 0.2 mg cm−2 sputtered IrOx shows the best OER performance. The composite IrOx/Pt/IrOx electrode demonstrated a bi-functional catalytic activity toward both OER and ORR, as well as improved gas diffusion properties toward ORR compared to the single Pt layer with the same catalytic loading.A phenomenological criterion for evaluating the gas diffusion properties of the electrodes is proposed. The applied testing approach is validated via comparison of the results obtained in the EasyTestCell and the common laboratory PEM electrolytic cell.
Electrochimica Acta. 54(4):1269-1276.
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ABSTRACT: This paper presents a novel electrochemical test cell for fast screening and optimisation of membrane electrode assemblies (MEAs) used in the hydrogen fuel cells and water electrolysers, called an “EasyTest” cell. The principle and the experimental possibilities of the cell are demonstrated in a study on the properties of nanostructured platinum films as electrocatalysts for hydrogen oxidation and generation. Platinum films are deposited by dc magnetron sputtering and are incorporated in MEAs with Nafion polymer electrolyte membrane. For comparison, results obtained using a MEA with commercially available Pt catalyst (ELAT (R) V.21, Lot # MB030105-1, Pt loading , E-TEK) are also presented. The catalytic activity is assessed applying the conventional electrochemical methods of cyclic voltammetry and steady state polarisation. XRD and SEM spectroscopy are used for morphological study of the sputtered films. The results demonstrate the advantages of the EasyTest cell and show that magnetron sputtering is a simple and reliable method for deposition of electrocatalysts with homogeneous particle distribution, reproducible surface morphology, and precisely controlled loading.
International Journal of Hydrogen Energy.
