Fuel cell degradation

REVIEW OF PEM FUEL CELL DEGRADATION PHENOMENA AND MECHANISMS... 

Ammonia, produced due to the coexistence of H2 and N2 at high temperatures in the presence of catalyst, was estimated to be in the concentration range of 30 to 90 ppm [37, 38], Uribe et al. [39] examined the effects of ammonia trace on PEM fuel cell anode performance and reported that a trace in the order of tens of parts per million could lead to considerable performance loss. They also used EIS in their work. By measuring the high-frequency resistance (HFR, mainly contributed by membrane resistance) with an operation mode of H2 + NH3/air (feeding the anode with hydrogen and ammonia), they obtained some information related to membrane conductivity, and found that conductivity reduction due to ammonia contamination is the major cause of fuel cell degradation. 

Figure 6.17. The two scenarios of fuel cell degradation, (a) Small A - 1 local current density exceeds the critical level right upon start-up. The degradation wave starts immediately, (b) A — 1 1 the critical current density initially exceedsXO). Due to the slow process of ageing, jcru decreases with time, and at some time moment the condition j 0 (0) = jcrit is fulfilled. This initiates slow and then fast propagation of the degradation wave.

Wu J, Yuan X Z, Martin J J, Wang H, Yu D, Qiao J and Merida J (2010b), Proton exchange membrane fuel cell degradation under close to open-circuit conditions Part I In situ diagnosis,/onma/ of Power Sources, 195,1171-1176. 

F.-Y. Zhang, S.G. Advani, A.K. Prasad, Advanced high resolution characterization techniques for degradation studies in fuel cells, in M.M. Mench, E.C. Kumbur, T.N. Vezirogju (Eds.), Polymer Electrolyte Fuel Cell Degradation, Academic Press,... 

In fact, this potential driven corrosion of carbon can be quite severe, causing substantial loss of the electrochemically active surface area as the electrode degrades with the loss of the catalyst support. Enhanced fuel cell degradation can occur under the additional stress conditions associated with cold start and hot stopping [62]. 

A fuel cell is a typical electrochemical device. Thus, the electrochemical analysis methods developed for other electrochemical devices can be directly used or modified for diagnosis of fuel cell degradation, including catalyst layer degradation. Cyclic voltammetry and polarization curve analysis are very frequently used in failure analysis and degradation diagnosis. 

Electrochemical methods used in the diagnosis of fuel cell degradation provide directly macro-phenomena about fuel cell degradation. Hypothesis and degradation mechanisms can be deduced from electric measurement results, e.g., from analysis of polarization curves. To fundamentally understand catalyst layer degradation in... 

NH3 is another typical contaminant in PEM fuel cell anodes. Trace amounts of NH3 in a fuel cell system will cause significant fuel cell degradation [82-86]. NH3 in the fuel stream originates mainly from hydrogen production and storage, due to several causes ... 

Kocha SS (2012) Electrochemical degradation electrocatalyst and support durability. In Kumbur EC, Veziroglu TN, Mench MM (eds) Polymer electrolyte fuel cell degradation. Academic, New York... 

Part I of the present volume includes the fundamentals and developments of the ESR experimental and simulations techniques. This part could be a valuable introduction to students interested in ESR, or in the ESR of polymers. Part II describes the wide range of applications to polymeric systems, from living radical polymerization to block copolymers, polymer solutions, ion-containing polymers, polymer lattices, membranes in fuel cells, degradation, polymer coatings, dendrimers, and conductive polymers a world of ESR cum polymers. It is my hope that the wide range of ESR techniques and applications will be of interest to students and mature polymer scientists and will encourage them to apply ESR methods more widely to polymeric materials. And I extend an invitation to ESR specialists, to apply their talents to polymers. 

The operational honrs expected for the application is only one factor in product durability requirements. Durability is also a significant function of operating conditions, material properties and product design. This chapter will focus on the impact of operating conditions on major PEM fuel cell degradation mechanisms. 

Major polymer electrolyte membrane (PEM) fuel cell degradation mechanisms... 

With the knowledge of Pt catalyst degradation mechanisms introduced above, it is easy to understand that PEM fuel cell performance decline is a complicated event involving many parallel factors. The normal relevant operating conditions include temperature, RH, potential, and contaminant. The following subsections will provide more information on the investigation of current durability, as well as the specific research methods used to explore fuel cell degradation mechanisms. 

Owing to the numerous parameters and complexity of carbon support oxidation, many other papers (Meyers and Darling, 2006 Hu et al., 2007,2008 Takeuchi and Fuller, 2007,2008 Bi et al., 2008 Franco et al., 2008 Franco and Gerard, 2008 Gidwani et al., 2008) not reported here describe models such as the ones proposed to investigate the different parameters effecting carbon corrosion and fuel cell degradation. 

This chapter deals with impacts of PEM fuel cell degradations ascribed to a subzero environment. 

He has published a series of seminal papers on the mechanisms of fuel cell degradation and possible scenarios of catastrophic worsening of the fuel cell performance, having described, for example, effects such as the degradation wave along the air channel in PEFCs, and Ru corrosion due to methanol depletion in DMFCs. He contributed to the explanation of exotic direct and reversed performance domains in PFFCs under the lack of hydrogen at the anode (in the reverse domain, carbon... 

Previous work includes a Failure Mode Identification (FMEA) and fault Tree Analysis (FTA) of a general PEMFC by Rama, et al. (2008). Additionally, a more recent FTA work was presented by Placca. L Kouta. R (2011), looking at the failure modes that could cause PEMFC degradation, yielding a more detailed fault tree of fuel cell degradation. 

Placca. L Kouta, R. 2011 Fault tree analysis for pern fuel cell degradation process modelling, International Journal of Hydrogen Energy, vol. 36. no. 19, 12 393-12 405. 

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