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A compact prototype system for H2 production based on a Polymer Electrolyte Membrane (PEM) stack was developed and investigated. A detailed study and an optimization of the Balance of Plant (BoP) was carried out. The system was developed in laboratory by using commercial devices tailored around in house-made membrane electrode assemblies (MEAs). The study regarded both the hydraulic circuit efficiency loss and its optimization by varying process parameters. Energy consumption for auxiliary devices was studied at different temperatures (40, 60 and 75 °C). Efficiency and control strategy management of the system were investigated. Despite an increase of stack performance observed at high temperature, maximum system efficiency (65% compared to HHV) was obtained at 40 °C because of moderate energy consumption by the electric heater. To evaluate the stack contribution to the overall efficiency, the present investigation was completed by a hydrodynamic study of the stack inside the system. Diffusional aspects related to the water mass distribution inside the stack were investigated through a computational fluid dynamic analysis (CFD). In particular, a 3D analysis of the whole stack composed by 120 channels and 10 cells was carried out. The model showed a quite uniform distribution of water over the individual channels and a homogeneous pressure inside the cells. Accordingly, the risk of having hot spots and gases accumulated inside the stack was minimal. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, the number of power plants based on renewable energy (RWE) has been increasing and hydrogen as an energy carrier has become a suitable medium-to-long term storage solution as well as a “fuel” for FCEV''s because of its CO2-free potential. In this context, the aim of the present study is to carry out both an economic and environmental analysis of a start-up RWE plant using a simulation code developed in previous work and a Life Cycle Assessment (LCA). The plant will be located in the South of Italy (Puglia) and will consist of different RWE sources (Wind Power, Photovoltaic, Biomass). RWE will be used to produce hydrogen from an electrolyzer, which will feed a fleet of buses using different fuels (methane, hydrogen, or a mixture of these). In particular, a wind turbine of 850 kW will feed a hydrogen production plant and a biomass plant will produce methane. Preliminary studies have shown that it is possible to obtain hydrogen at a competitive cost (DOE target) and that components (wind turbine, electrolyzer, vessel, etc.) influence the final price. In addition, LCA results have permitted a comparison of different minibuses using either fossil fuels or renewable energy sources. [Copyright &y& Elsevier]

High electrochemical efficiency at elevated current densities and low H 2 concentration in O 2 can be achieved in PEM electrolysis using thin membrane and integrated recombination catalyst. An enhanced PtCo alloy recombination catalyst was synthesized and used at the anode of a membrane-electrode assembly (MEA). This allowed reducing the H 2 concentration in the oxygen stream during electrolysis operation with a thin 50 μm perfluorosulfonic acid (PFSA) Aquivion® membrane. Both dual-layer and composite anode configurations (PtCo/IrRuOx) were investigated. The electrochemical performance of the MEAs containing the recombination catalyst was better than a bare MEA while producing a decrease of the H 2 content at the anode. This allowed extending the partial load operation down to 5% at 55 °C under a differential pressure of 20 bar. The effects of the cathodic pressure and cell temperature (including evaluation of intermediate temperature operation at 140 °C) on both electrochemical performance and H 2 concentration in the anode stream were investigated. An excellent performance of 4 A cm−2 at 1.75 V, at 140 °C, 20 bar cathode pressure, 5.5 bar anode pressure, with 0.6 mg cm−2 overall precious metal catalysts content was recorded. At 140 °C, the MEA also showed a moderate H 2 concentration in O 2 of about 2.3%, almost constant through most of the current density range. Image 1 • MEA-integrated PtCo catalyst reduces H 2 concentration in O 2 up to 140 °C. • Performance of 4 A cm−2 at 1.75 V, 140 °C, 20 bar cathode pressure is achieved. • PtCo recombination catalyst allows using thin (50 μm) membranes in electrolysis. • A PtCo-IrRuOx composite layer shows a H 2 concentration in O 2 lower than a dual-layer. • Low partial load operation of 5% at 55 °C at 20 bar differential pressure is achieved. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical properties of a proton exchange membrane (PEM) stack electrolyzer (9 cells of 100 cm2 geometrical area) were investigated at different temperatures. An amount of H2 of ∼270 l h−1 was produced at 60 A (600 mA cm−2) and 70 °C under 876 W of applied electrical power. The corresponding specific energy consumed in the process was 3.24 Wh·l−1H2. The Faradic and electrical efficiencies were determined. Overall stack efficiencies of 73% and 85%, at 60 A and 70 °C, with respect to the low and high heating value of hydrogen, respectively, were obtained. These results confirmed the successful scale-up of a previous lab-scale device. [Copyright &y& Elsevier]

Abstract: An investigation of components degradation in a polymer electrolyte membrane (PEM) electrolyzer technology for naval application is carried out. In naval applications, an electrolyzer has to work using treated seawater obtained on board. Electrolyzer performance is evaluated in terms of hydrogen production per unit of electrical energy input starting from a seawater desalination plant simulating the conditions on board of the ship. A desalinator plant, tailored for the specific application, is designed to produce water having a low ionic conductivity (<5 μS) compatible with the PEM stack electrolyzer requirements. Electrochemical characterizations are carried out on an in-house developed 9-cells PEM electrolyzer by using treated water. Several aspects related with the degradation of materials and components electrolyzer are investigated under oxidizing atmosphere. Specific tests are carried out in a corrosive ambient that simulates the sea environment in terms of humidity, salinity, corrosive conditions etc… In order to simulate highly oxidizing atmosphere, a Dry Corrosion Test Cabinet (DCTC®) is used to test MEAs and electrolyzer components on the basis of specific international norms (ASTM standard). Both materials and components are characterized by electrochemical and physico-chemical analysis before and after the DCTC® treatment. [Copyright &y& Elsevier]

Abstract: An optimization study of components and assembling characteristics for a proton exchange membrane (PEM) short stack electrolyzer (3 cells of 100 cm2 geometrical area) was carried out. The electrochemical properties were investigated by polarization, impedance spectroscopy and chrono-potentiometric measurements. A decrease of the ohmic contact resistance between the bipolar plates and the electrode backing layer was obtained by using an appropriate thickness for the gas diffusion layers/current collectors as well as by an optimization of stack compression. The amount of H2 produced was ∼90 l h−1 at 60 A (600 mA cm−2) and 75 °C under 300 W of applied electrical power. No significant leakage or gas recombination was observed. The stack electrical efficiency was 75% and 88%, at 60 A and 75 °C, with respect to the low and high heating value of hydrogen, respectively. [Copyright &y& Elsevier]

Abstract: A nanosized IrO2 anode electrocatalyst was prepared by a sulfite-complex route for application in a proton exchange membrane (PEM) water electrolyzer. The physico-chemical properties of the IrO2 catalyst were studied by termogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrochemical activity of this catalyst for oxygen evolution was investigated in a single cell PEM electrolyzer consisting of a Pt/C cathode and a Nafion® membrane. A current density of 1.26Acm−2 was obtained at 1.8V and a stable behavior during steady-state operation at 80°C was recorded. The Tafel plots for the overall electrochemical process indicated a slope of about 80mVdec−1 in a temperature range from 25°C to 80°C. The kinetic and ohmic activation energies for the electrochemical process were 70.46kJmol−1 and 13.45kJmol−1, respectively. A short stack (3 cells of 100cm2 geometrical area) PEM electrolyzer was investigated by linear voltammetry, impedance spectroscopy and chrono-amperometric measurements. The amount of H2 produced was 80lh−1 at 60A under 330W of applied electrical power. The stack electrical efficiency at 60A and 75°C was 70% and 81% with respect to the low and high heating value of hydrogen, respectively. [Copyright &y& Elsevier]