M. De Francesco

Comparison of high surface Pt/C catalysts by cyclic voltammetry

A detailed procedure for comparing high surface Pt/C catalysts was pointed out. Platinum dispersed carbon was prepared from carbonaceous material and chloroplatinic acid solution using sodium formiate. The real platinum metal surface area was evaluated by cyclic voltammetry on a thin porous coated disk electrode. The performance of catalysts prepared in our laboratory were similar to those of a well-known commercial one. The results show that electrochemical active surface (EAS) measurement is strongly influenced by the gas diffusion electrode (GDE) preparative method. It is only by means of a well-defined preparative procedure and data analysis that it is possible to use this technique to compare different carbon supported platinum catalysts.

Nafion degradation in PEFCs from end plate iron contamination

Nafion degradation in polymer electrolyte fuel cells from SS316L end plate iron contamination was tested in a single cell configuration. Water collected at the cathode and anode exhausts was analysed by means of pH measurements, conductivity, fluoride and metal concentration. The investigations revealed that stainless steel is unsuitable as material for end plates in PEM fuel cells. In fact, iron contamination of membrane electrode assemblies led to polymer degradation, revealed by a massive fluoride loss. In contrast, iron-free plates (aluminium alloy) showed higher stability in the cell environment.

Start-up analysis for automotive PEM fuel cell systems

Abstract The development of fuel cell cars can play an important role in resolving transport problems, due to the high environmental compatibility and high efficiency of this kind of vehicle. Among the different types of fuel cells, proton-exchange membrane fuel cells (PEMFCs) are considered the best solution for automotive applications at the moment. In this work, constructive criteria are discussed with the aim of obtaining a power generation module adaptable to a wide range of cars. A particular problem in accomplishing the overall project is represented by the definition of the compressor system for air feeding. In this work, the design approach to the problem will be delineated: some options are reviewed and the best solution is analysed. The transient response of the system (fuel cell and compressor) is investigated in order to optimise the start-up running through a model of a fuel cell stack and a compressor simulation. The model and its results are proposed as a work procedure to solve the problem, by varying external conditions: in fact, to perform the system start-up under stable conditions, the air relative humidity and temperature must be maintained in a proper range of values. The approach here presented has been utilised for the definition of the characteristics of the power module and layout of a middle-size hybrid city bus in the framework of a project promoted by the European Union.

A novel route to prepare stable Pt-Ru/C electrocatalysts for polymer electrolyte fuel cell

A new method for preparing high surface Pt–Ru/C catalysts at low temperature is described. Pt–Ru on carbon was prepared from carbonaceous material, Pt(NH3)4Cl2 and RuNO(NO3)x(OH)y with borohydride as a reducing agent. Simultaneous reduction of both metals was provided by means of heat treatment. Small and homogeneously dispersed catalyst particles were obtained. XRD and electrochemical measurements show that the performance of the catalyst prepared was similar to that of commercial E-Tek samples, but with increased stability.

Catalytic membrane reactors for tritium recovery from tritiated water in the ITER fuel cycle

Abstract Palladium and palladium–silver permeators have been obtained by coating porous ceramic tubes with a thin metal layer. Three coating techniques have been studied and characterized: chemical electroless deposition (PdAg film thickness of 10 μm), ion sputtering (about 1 μm) and rolling of thin metal sheets (50 μm). The Pd-ceramic membranes have been used for manufacturing catalytic membrane reactors (CMR) for hydrogen and its isotopes recovering and purifying. These composite membranes and the CMR have been studied and developed for a closed-loop process with reference to the design requirements of the international thermonuclear experimental reactor (ITER) blanket tritium recovery system in the enhanced performance phase of operation. The membranes and CMR have been tested in a pilot plant equipped with temperature, pressure and flow-rate on-line measuring and controlling devices. The conversion value for the water gas shift reaction in the CMR has been measured close to 100% (always above the equilibrium one, 80% at 350°C): the effect of the membrane is very clear since the reaction is moved towards the products because of the continuous hydrogen separation. The rolled thin film membranes have separated the hydrogen from other gases with a complete selectivity and exhibited a slightly larger mass transfer resistance with respect to the electroless membranes. Preliminary tests on the sputtered membranes have also been carried out with a promising performance. Considerations on the use of different palladium alloy in order to improve the performances of the membranes in terms of permeation flux and mechanical strength, such as palladium/yttrium, are also reported.

Immobilisation of engineered molecules on electrodes and optical surfaces

Abstract Monolayers of genetically modified proteins with an hexahistidine tag, (His) 6 , were obtained by using a Ni–NTA chelator synthesized on gold-sputtered surfaces (via sulphide bonds), or on gold and graphite (via sililating agents) working electrodes of screen-printed devices. Two kinds of proteins were produced and purified for this study: (a) a recombinant antibody, derived from the ‘single-chain Fv’ (scFv) format, and (b) a photosystem II (PSII) core complex isolated from the mutant strain CP43-H of the thermophilic cyanobacterium Synechococcus elongatus . An scFv previously isolated from a synthetic ‘phage display’ library was further engineered with an alkaline phosphatase activity genetically added between the carboxy-terminal of the scFvs and the (His) 6 to allow direct measurement of immobilisation. Renewable specific binding of (His) 6 proteins to gold and graphite surfaces and fast and sensitive electrochemical or optical detection of analytes were obtained. Additionally, “on chip” protein preconcentration was conveniently achieved for biosensing purposes, starting from crude unpurified extracts and avoiding protein purification steps.

Membrane electrode gasket assembly (MEGA) technology for polymer electrolyte fuel cells

A new technology for the production of a membrane electrode gasket assembly (MEGA) for polymer electrolyte fuel cells (PEFCs) is defined. The MEGA system was prepared by sealing a previously prepared membrane electrode assembly (MEA) in a moulded gasket. For this aim, a proprietary silicone based liquid mixture was injected directly into the MEA borders. Gaskets obtained in different shapes and hardness grades are stable in a wide temperature range. The MEGA technology shows several advantages with respect to traditional PEFCs stack assembling systems: effective membrane saving, reduced fabrication time, possibility of quality control and failed elements substitution. This technology was successfully tested at the ENEA laboratories and the results were acquired in laboratory scale, but industrial production appears to be simple and cheap.