Fuel cell performance Introduction

The introduction of such a layer can dramatically improve the fuel cell performance. For example, in the SOFC with bilayered anode shown in Figure 6.4, the area-specific polarization resistance for a full cell was reduced to 0.48 Hem2 at 800°C from a value of 1.07 Qcm2 with no anode functional layer [24], Use of an immiscible metal oxide phase (Sn()2) as a sacrificial pore former phase has also been demonstrated as a method to introduce different amounts of porosity in a bilayered anode support, and high electrochemical performance was reported for a cell produced from that anode support (0.54 W/cm2 at 650°C) [25], Use of a separate CFL and current collector layer to improve cathode performance has also been frequently reported (see for example reference [23]). 

Work with industry partners to validate model predictions and perform studies that support fuel cell technology introductions... 

Another prorrtising modification of PBI is the introduction of immobilized polyvirtylphosphonic acid (PVPA) in the PBI matrix. This approach is especially interesting since the acid is not likely to be washed out dttring operation, thus maintaining steady fuel cell performance. PEMEAS-BASF Fuel Cells has developed an MEA product, Celtec -V, mainly for liqttid feed DMFCs, based on this concept Single-cell performance tests of CeltecV and Na... 

This means that at the time of mass-market introduction, their expected lifetime needs to be 5,000 h, with an end of life performance, which is at least 90% of the performance at the beginning of life. No external conditions, except for severe crashes, might lead to severe deterioration of the fuel cell performance. In practice, this means that the fuel cell system needs to operate between 40°C and +50°C ambient temperature, under aU relative humidities. 

Semiempirical Model for Fuel Cell Performance in the Presence of Toluene In the presence of toluene in the air stream, the fuel cell performance degraded. Figure 3.15 illustrates two sets of representative results of toluene contamination tests, conducted with various levels of toluene concentration at current densities of 0.75 and 1.0 A cm , respectively. The cell voltage experienced a transient period (nonsteady state) immediately after the introduction of toluene, then reached a plateau (steady state). The duration of the transient period and the magnitude of the cell voltage drop to the plateau were strongly dependent on toluene concentration and current density. 

This chapter mainly deals with the fundamentals of H2/air PEM fuel cells, including fuel cell reaction thermodynamics and kinetics, as well as a brief introduction to the single fuel cell and the fuel cell stack. The electrochemistry and reaction mechanisms of H2/air fuel cell reactions, including the anode HOR and the cathode ORR, are discussed in depth. Several concepts related to PEM fuel cell performance, such as fuel cell polarization curves, OCV, hydrogen crossover, and fuel cell efficiencies, are also introduced. With respect to fuel cell stmctures and components, the material properties and effects on fuel cell performance are also discussed. In addition, several important conditions for fuel cell operation, including temperature, pressure, RH, and gas stoichiometries and flow rates, and their effects on fuel cell operation, are also briefly presented. This chapter provides the requisite baseline knowledge for the remaining chapters. 

The various types of fuel cells are at somewhat different stages in the technology cycle the MCFC is ready for market introduction but faces the typical problem of a new technology, i.e., is expensive because of the lack of economies of scale for its production and the lower cost of its technical rivals (engine-driven co-generation and microturbines). From the technical point of view, the phase of euphoria has almost passed for PEMs and SOFCs and further R D activities are necessary for these two types to match the technical performance of their competitors or the necessary cost level for fuel cells to be technologically and economically ripe for the market. Only the DMFC has reached a standard that allows its use in niche markets, like caravans or yachts, despite poor efficiency levels. 

Wholly aromatic polymers are thought to be one of the more promising routes to high performance PEMs because of their availability, processability, wide variety of chemical compositions, and anticipated stability in the fuel cell environment. Specifically, poly(arylene ether) materials such as poly-(arylene ether ether ketone) (PEEK), poly(arylene ether sulfone), and their derivatives are the focus of many investigations, and the synthesis of these materials has been widely reported.This family of copolymers is attractive for use in PEMs because of their well-known oxidative and hydrolytic stability under harsh conditions and because many different chemical structures, including partially fluorinated materials, are possible, as shown in Figure 8. Introduction of active proton exchange sites to poly-(arylene ether) s has been accomplished by both a polymer postmodification approach and direct co-... 

The energy efficient automobile is also a perfect starting point for subsequent introduction of fuel cell drives, where one would no longer need to put a 65-100 kW fuel cell in to get a decent performance and hence could do with smaller on-board hydrogen storage pressure and get a safer system still... 

Besides the effects of the typical carbon functional groups, the role of nitrogen and sulfur functionalities, introduced on carbons by chemical and thermal treatments, on the electrochemical performance of Pt catalysts for oxygen reduction in direct methanol fuel cells was investigated [47]. Once again, the metal-support interaction influences the size and chemical state of platinum particles and, as a consequence, the electrocatalytic activity. The introduction of nitrogen and sulphur functionalities was reported to improve the catalytic activity, but this result was mainly ascribed to the Pt particle size. 

This introduction illustrates that the membrane is one key material component of a fuel cell whose properties limit the achievable performance. The ideal fuel cell membrane should... 

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