Lidia Pino

Modeling polymer electrolyte fuel cells: an innovative approach

Abstract In this paper, a mathematical simulation model is proposed to describe the water transport in proton conductive membranes, used in polymer electrolyte fuel cells (PEFCs). The model, which includes the calculation of electrochemical parameters of a PEFC, represents a quite innovative approach. In fact, it is based on the use of original mathematical relationships taking into account diffusional and ohmic overpotentials for electrode flooding and membrane dehydration problems. The calculated performance of polymer fuel cells using a Nafion 117 membrane clearly demonstrates the model validation (±3% variation with respect to experimental data). Besides, analysis of model results allows a useful comparison of two different membranes (Nafion 117, Dow) in order to define the best membrane/electrode assembly.

A comparative study of Pt/CeO2 catalysts for catalytic partial oxidation of methane to syngas for application in fuel cell electric vehicles

In the framework of a project aimed at developing a reliable hydrogen generator for mobile polymer electrolyte fuel cells (PEFCs), particular emphasis has been addressed to the analysis of catalysts able to assure high activity and stability in transient operations (frequent start-up and shut-down cycles). In this paper, the catalytic performance of 1 at.% Pt/ceria samples prepared by coprecipitation, impregnation and combustion, has been evaluated in the partial oxidation of methane. Methane conversion and hydrogen selectivity of 96 and 99%, respectively, associated with high stability during 100 h of reaction under operative conditions (start-up and shut-down cycles), have been obtained.

Catalytic partial-oxidation of methane on a ceria-supported platinum catalyst for application in fuel cell electric vehicles

Fuel cell developers are investigating the generation of hydrogen from light hydrocarbons, such as methane or natural gas, for fuelling polymer electrolyte fuel cells (PEFCs). This study demonstrates generation of H 2 and CO by catalytic partial-oxidation of CH 4 in air at atmospheric pressure on a ceria-supported platinum catalyst prepared by a novel solution-combustion method where platinum is present in ionically-substituted form. These catalysts at different platinum loadings showed methane conversion and hydrogen selectivity of 90 and 97%, respectively. Interestingly, there is little carbon deposition in the catalytic reactor even after prolonged reaction time.

Hydrogen generator, via catalytic partial oxidation of methane for fuel cells

Abstract It is well known that the most acknowledged process for generation of hydrogen for fuel cells is based upon the steam reforming of methane or natural gas. A valid alternative could be a process based on partial oxidation of methane, since the process is mildly exothermic and therefore not energy intensive. Consequently, great interest is expected from conversion of methane into syngas, if an autothermal, low energy intensive, compact and reliable process could be developed. This paper covers the activities, performed by the CNR Institute of Transformation and Storage of Energy (CNR-TAE), on theoretical and experimental studies for a compact hydrogen generator, via catalytic selective partial oxidation of methane, integrated with second generation fuel cells (EC-JOU2 contract). In particular, the project focuses the attention on methane partial oxidation via heterogeneous selective catalysts, in order to: demonstrate the basic catalytic selective partial oxidation of methane (CSPOM) technology in a subscale prototype, equivalent to a nominal output of 5 kWe; develop the CSPOM technology for its application in electric energy production by means of fuel cells; assess, by a balance of plant analysis, and a techno-economic evaluation, the potential benefits of the CSPOM for different categories of fuel cells.

Characterization of the morphological modification induced by long term operations on phosphoric acid fuel cell (PAFC) electrodes

The modification of the morphological and adhesive binding of PAFC electrodes has been studied by electron spectroscopy and electron microscopy with regard to their endurance and preparative treatments. The corrosion of the electrodes has been found to dramatically affect the electrical and adhesive contact between PTFE (polytetrafluoroethylene) and active carbon. This has been detected in X-ray photoelectron spectroscopy (XPS) by the ‘charging’ shift seen for F 1 s due to the loss in electronic contact between these components. In addition, the adhesive character of the contact between the SiC matrix and the gas diffusion electrodes has been revealed by the XPS spectral characteristics. Here a major difference between the anode and the cathode has been observed with the cathode having a greater deadhesion. Extensive physical characterization by pore volume and size distribution, wetting, and weight loss has been performed. These results have been correlated with the XPS results to give a complete model of the deterioration of this technologically important system. A possible explanation for the observed loss of PTFE from the surface of the cathode based on an electrostatic rejection model of the delaminated PTFE particles is also suggested.

Sorbents with high efficiency for CO2 capture based on amines-supported carbon for biogas upgrading

Sorbents for CO2 capture have been prepared by wet impregnation of a commercial active carbon (Ketjen-black, Akzo Nobel) with two CO2-philic compounds, polyethylenimine (PEI) and tetraethylenepentamine (TEPA), respectively. The effects of amine amount (from 10 to 70wt.%), CO2 concentration in the feed, sorption temperature and gas hourly space velocity on the CO2 capture performance have been investigated. The sorption capacity has been evaluated using the breakthrough method, with a fixed bed reactor equipped with on line gas chromatograph. The samples have been characterized by N2 adsorption-desorption, scanning electron microscopy and energy dispersive X-ray (SEM/EDX). A promising CO2 sorption capacity of 6.90 mmol/gsorbent has been obtained with 70wt.% of supported TEPA at 70°C under a stream containing 80vol% of CO2. Sorption tests, carried out with simulated biogas compositions (CH4/CO2 mixtures), have revealed an appreciable CO2 separation selectivity; stable performance was maintained for 20 adsorption-desorption cycles.

Effect of platinum particle size on the performance of PAFC O2 reduction electrocatalysts

Abstract The influence of the electrocatalyst characteristics upon activity and stability for the oxygen reduction reaction in phosphoric acid fuel cell (PAFC) systems is widely established. The initial catalytic performance progressively decreases, even on a short-term basis, under operational conditions, due to several factors such as Pt dissolution, sintering and carbon corrosion. The performance of catalysts depends upon the morphological characteristics of the electrodes. The proper tailoring of the Pt/C catalyst plays a fundamental role in obtaining high overall performance in such electrochemical devices. A high mass activity (mA mg−1) and low voltage decay are found, in the present investigation, for catalysts having Pt surface area above 80 m2g−1. Such results have been tentatively interpreted in terms of the acid-base properties of the surface, as determined by a potentiometric titration technique.

Biogas Reforming for Hydrogen Production: Performance of Ni/La-Ce-O Catalysts

Biogas, a renewable source of CH4 and CO2, is used for hydrogen generation by tri-reforming 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.

Steam Reforming, Partial Oxidation, and Autothermal Reforming of Ethanol for Hydrogen Production in Conventional Reactors

Abstract The hydrogen production from ethanol by conventional steam reforming, partial oxidation, and autothermal reforming processes is investigated. A comparable analysis of processes configuration, reforming reactors, and catalyst features is provided. The processes are analyzed from theoretical and practical point of view, outlining the process efficiency for distributed application. The role of the catalyst and the process conditions in determining the ethanol conversion and the hydrogen yield is also elucidated.

Development of a Subscale Hydrogen Generator Unit for SOFC as APU for Naval Applications

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.