Fuel cell applications, membrane requirements stationary application

Two major barriers to the commercialization of PEM fuel cells are high cost and poor durability. The US Department of Energy has established the durability target of electrolyte membranes for automotive fuel cells at 5,000 h and for stationary fuel cells at 40,000 h with additional cost constraints and operation requirements. In commercial applications, the integrity of fuel cell membranes must... 

Figures for the time required for a smooth operation of polymer electrolyte membrane fuel cells (and other fuel cells used in the same applications) are given variously as 2000-3000 h for the power plants in portable devices, as up to 3000 h over a period of 5-6 years for the power plants in electric cars, and as 5-10 years for stationary power plants. Much time will, of course, be required to collect statistical data for the potential lifetime of different kinds of fuel cells. Research efforts, therefore, concentrate on finding the reasons for the gradual decline of performance indicators and for premature failure of fuel cells. In recent years, many studies have been conducted in this area.

Proton-exchanging membrane fuel cells (PEMFC) are considered to be one of the most promising types of electrochemical device for power generation [1-10]. Low operation temperatures and the wide range of power make them attractive for portable, automotive, and stationary applications. However, advances made in these markets require further cost reduction and improved reliabiUty. These can be achieved through development and implementation of novel proton-exchange membranes with higher performance and lower cost as compared to the state of the art polymeric electrolytes. 

For stationary applications a PEM fuel cell is required to operate for 40,000 hours or longer. The major MEA failure modes that lead to a much shorter lifetime are the membrane breach and the electrode decay. The former will result in reactant crossover that causes a sudden and catastrophic failure. lonomer chemical structure and end-group modification, reinforcement of the membrane, incorporation of additives into the membrane, and use of a protective subgasket or full-gasket are effective methods to slow down the membrane breach process. The electrode decay causes gradual loss of the fuel cell performance and rarely causes catastrophic failures. The performance decay lowers the fuel cell efficiency and when the efficiency becomes lower than a predetermined value, the fuel cell reaches its end of life. In... 

Recently, the number of studies devoted to the development of anion exchange membranes has significantly increased. There are numerous examples of relatively high-ion exchange capacity membranes, with respectable OH conductivity that exceeds the minimum conductivity requirements, for instance, for fuel cell stationary applications. 

The performanee and durability of a membrane electrode assembly (MEA) is affected signifieantly by the eathode eleetrode eomposition and structure, due to the poor kineties of oxygen reduetion and reaetant transport limitations. Utilization and stability of platinum or its alloys in the PEMFC play important roles in fuel cell efficiency, durability, and the drive for eost reduction through reduced Pt loadings. Cathode catalyst layer degradation is a critical issue for fuel cell durability to meet the requirement of > 5000 hours for automotive applications and > 40,000 for stationary applications. 

With the trend to higher temperature of fuel cell operation, as is needed for both automotive and stationary applications, and the requirement for high performance, recent developments have tended towards the use not only of low-EW PFSA polymer membranes, but also in the employment of membranes of thickness only 25-30 pm (compared with the use of films of ca. 175 pm ten years ago) for their lower area specific resistance and increased water permeation rate, and both of these factors impact the membrane s mechartical strength. The difficulty lies in... 

Abstract The durability of fuel cell components constitutes a major barrier towards their financial viabihty. Lifetime requirements include 5000 and 40 000 h for automotive and stationary applications respectively, and thus it is impractical to evaluate fuel cell components lifetime using prolonged time periods. Accelerated durability testing protocols for fuel cell components (proton exchange membrane, electrocatalyst and supports) have been developed to obtain cell component lifetimes in shorter e q)erimental time and are discussed in detail, along with fiiel/air impurities testing protocols. 

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