Year 2016, Volume 36

Abstract

This paper covers the current activities at the CNR-ITAE aimed to developing a diesel steam reforming (SR) Hydrogen Generator based unit, dedicated to a Solid Oxide Fuel Cell (SOFC) in a power range until 1 kWe, to support auxiliary power units (APUs) for naval applications. The unit will is able to convert n-dodecane, as a diesel surrogate, with a nominal syngas production of 0.5 Nm³/h and a maximum hydrogen production of 1.5 Nm³/h. The prototype is based on an integrated packed bed catalytic tubular reactor, filled with pellet catalysts. In the preliminary laboratory scale tests, dodecane conversion of 99,9 %, in absence of by products, have been evidenced; the H₂/CO molar ratio in the reformed gas reaches a value of 3.8.

Abstract

Dense micrometric La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM) films were deposited by spincoating on porous LSGM scaffolds characterized by an homogeneous pore structure. Porous anodes were infiltrated with aqueous nickel nitrate solutions, dried and fired at 700 °C. Homogeneous metal coating with proper interconnections was observed by SEM, chemical stability was confirmed by XRD. Fuel cell tests and electrochemical impedance spectroscopy (EIS) were performed and discussed.

Abstract

A “cobalt free” cathode material with stoichiometric composition La_0.8Sr_0.2Fe_0.8Cu_0.2O₃ (LSFCu) was specifically developed for La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ (LSGM) electrolyte. The chemical stability with LSGM electrolyte was investigated by structural and morphological analysis. The electrochemical properties of LSFCu dense pellets were investigated in the temperature range 600–750°C by electrochemical impedance spectroscopy (EIS). LSFCu/LSGM/LSFCu symmetrical cells were prepared and Area Specific Resistance (ASR) values, directly depending on the rate limiting step of the oxygen reduction reaction, were evaluated. Fuel cells were prepared using LSFCu as cathode material on LSGM pellet and electrochemical tests were performed and compared to similar fuel cells prepared by using commercial La_0.6Sr_0.4Fe_0.8Co_0.2O₃(LSFCo). The maximum current density and power density recorded for LSFCu and LSFCo were comparable demonstrating that Cu can be used as substitutes Co.

Abstract

Biogas, a renewable source of CH₄ and CO₂, is used for hydrogen generation by trireforming reaction; the reaction is a combination of CO₂ reforming, steam reforming and partial oxidation of CH₄ in a single catalytic step.
Several Ni/La-Ce-O mixed oxides, prepared by combustion synthesis, were used as catalysts. The experimental tests, carried out with synthetic biogas at 800°C with a gas hourly space velocity (GHSV) of 30000 h^-1, were aimed to study the influence of different parameters (amount of La doping, Ni load and feed composition) on the catalysts activity and stability. The synergic effect of nickel-lanthana-surface oxygen vacancies of ceria influences the samples activity.

Abstract

The present work focuses on the electrical properties of La_2–xCa_xNiO_4+δ (x=0–0.4) and
the electrochemical performance of the cathodes based on these materials with a LаNi_0.6Fe_0.4O_3-δ current collector in contact with a Ce_0.8Sm_0.2O_1.9 electrolyte. The effect of the sintering temperature on the polarization resistance of La_1.7Ca_0.3NiO_4+δ–Ce_0.8Sm_0.2O_1.9 composites of different content has been studied by an impedance spectroscopy method. The composite electrode 50 wt.% La_1.7Ca_0.3NiO_4+δ – 50 wt.% Ce_0.8Sm_0.2O_1.9 sintered at the temperature below 1300ºC has showed the lowest polarization resistance value equal to 0.27 Ωcm² and in case of PrO_x infiltration 0.033 Ωcm² at 800ºC in air.

Abstract

Low temperature fuel cells are one of the most promising systems for the transformation of fuels into electricity in an efficient, silent, and environmentally friendly manner. In this paper we show the advances accomplished in the synthesis and a theoretical-experimental analysis of the changes induced by the Ni@Pt structure and the presence of the almost unavoidable NiO species. The synthesis of core-shell nanoparticles is described and then physical and electrochemical characterizations confirm the presence of core-shell nanoparticles with a high electrochemical activity towards the Oxygen Reduction Reaction. Periodic density functional theory calculations are used to analyze the shift in the oxidation potential for Pt, Ni@Pt and NiO@Pt with different number of layers in the shell. The changes in the electrochemical activity towards oxygen reduction are evaluated by allowing oxygen to adsorb on the surface of the nanoparticle and alloys. It is found that only the first and second layers of Pt are being affected by the presence of the Ni or NiO core.

Abstract

The objective of this work is to study the behavior of Nitrogen-doped carbons as supports of catalysts for the electro-oxidation of methanol. Two carbon materials have been considered: a) carbon xerogels (CXG), highly mesoporous, whose porosity and pore size distribution are easily performed during the synthesis method; b) carbon nanofibers (CNF), which have a high electrical conductivity, good behavior in high temperature conditions and resistance to acid/basic media. Meanwhile, a commercial carbon black (Vulcan XC72R) which is commonly used in manufacturing of electrocatalysts fuel cells was used for comparison. Nitrogen was introduced into the CXG during the synthesis process, what is commonly referred as doping, by including melamine as a reactant. In contrast, N-groups were created over CNF by post-treatment with: ammonia (25%), urea (98%), melamine (99%) and ethylenediamine (99.5%), with a carbon: nitrogen molar ratio 1:0.6. N-containing carbon materials were characterized by elemental analysis, nitrogen adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), SEM-EDX and TEM to determinate the amount and forms of nitrogen introduced. Pt-catalysts were prepared by the microemulsion method. The influence of the nitrogen doping and functionalization on the catalytic behavior in the electrochemical oxidation of methanol was evaluated by different physicochemical and electrochemical analysis.

Abstract

Novel electrocatalysts from iron phthalocyanine (FePc) and polyindole (PID) supported on carbon nanotubes (CNTs) have been synthesized for oxygen reduction reaction (ORR) in Direct Methanol Fuel Cell (DMFC). Two synthetic strategies have been proposed: i) preparation of PID on CNTs (PID/CNTs) through indole polymerization followed by the mechanical mixing of PID/CNTs with FePc (FePc_PID/CNTs); and ii) dispersion of polymerized PID, FePc, and CNTs in methanol and subsequent drying (FePc/PID/CNTs). The morphology of prepared catalysts was examined by SEM, and the electrochemical activity towards ORR was evaluated by cyclic voltammetry. FePc/PID/CNTs catalysts were found to have higher activity than that of FePc_PID/CNTs, due to a better dispersion of PID and FePc on carbon support, as demonstrated by SEM. Furthermore, in comparison with platinum on carbon black the prepared PID-based catalysts exhibited a stable ORR potential in both H₂SO₄ and H₂SO₄ + CH₃OH solution. These new iron-based catalysts are thus promising to substitute platinum/carbon black at the cathode side of DMFC.

Abstract

Direct Methanol Fuel Cells (DMFC) are an attractive power source for applications in the low kW-range like pallet trucks or uninterruptable power supplies. A significant problem during the past years, however, was the limited durability of DMFC systems. While single cells could be operated for thousands of hours, DMFC systems degraded significantly often within less than 1,000 hours. In an evolution of six generations of DMFC systems in the kW power range over the past decade, we identified the main reasons for degradation. Causes for fast degradation had to be removed first in order to identify what leads to slower degradation over several hundreds or thousands of hours. Interactions of cells and system components also had to be considered. As a result, the operating conditions of all cells must be carefully controlled by suitable operating algorithms and reproducible manufacturing technologies, in order to avoid high potentials on the anode, which would lead to ruthenium corrosion and subsequent poisoning of the cathode catalyst. All components of the stack and the peripheral system must be corrosion-proof and free from contaminants that might leach into the membranes. Finally, a DMFC system for a pallet truck was operated in a realistic load cycle for 20,000 hours.

Abstract

Direct Methanol Fuel Cells (DMFCs) have been postulated as suitable systems for power generation in the fields of portable power sources, remote and micro-distributed energy generation, and auxiliary power units (APU). The main objective of the DURAMET project ((http://www.duramet.eu) is to develop cost-effective components for DMFCs with enhanced activity and stability in order to reduce stack costs and improve performance and durability. The project concerns with the development of DMFC components for application in auxiliary power units and portable systems.

Abstract

Direct methanol fuel cell stacks, with different architectures have been developed. A fuel cell planar stack, operating in passive mode, has been designed for portable application. The device consists of 10 cells, with nominal power of 1.00 – 2.42 W, single cell active area of 4.85 cm², nominal current of 1.00 A, at room pressure and temperature. Two printed circuit boards have been chosen to clamp and support the MEA and to electrically connect the active areas via conductive pathways. To investigate the stack performance, 4 different boards with different feeding holes shape have been designed. For high temperature operation purpose, a device with “stacked” configuration has been designed and manufactured. Operating parameters are: nominal power of 150W, single cell active area of 100 cm², nominal current of 25 A, cell number of 10. Promising results have been obtained both for APU and portable applications.

Abstract

A composite anode was investigated with the aim of enhancing the performance of direct methanol fuel cells (DMFCs). Fine iridium oxide nanoparticles were synthesized by a sulfite complex method. These IrO2 nanoparticles were mixed by sonication with a 50% PtRu/C catalyst prepared by the same procedure, considered as benchmark anode catalyst. A significantly higher performance was recorded for the composite electrode compared to the bare one based only on PtRu/C. The results confirm that the electrocatalytic activity is related to the characteristics of water displacement of the additive, evidencing that a multifunctional catalyst can operate better than PtRu for methanol oxidation since this multi-step process requires different functionalities to speed up the reaction rate.