Accelerators durability

Clearly, further work is necessary to elucidate the effect of long-term operation on PtRu and PtMo durability. However, given the length of experiments necessary to show such effects, the need to establish accelerated durability protocols for reformate anodes is clear. 

The above-mentioned codes contain requirements for accelerated durability tests. In addition, interlayer manufacturers and laminators expose test samples for several years under extreme weather conditions, eg, the Florida coast and Arizona desert. The laminated products weather extremely well, with no change in the plastic interlayer. Occasionally, clouding is noted around the edges when exposed to high humidity for long periods, but this is reversible. Colored areas of PVB laminates may fade while subjected to extensive uv/solar irradiation, which could cause an appearance issue. This has not, however, been shown to alter the laminate s other performance properties. 

So far, various studies focused on developing catalyst materials with improved ORR activity, but only few reported the stability and durability of ORR catalysts. The study of accelerated durability tests (ADT) in conjunction with electron microprobe analysis (BMPA), LEED, and XRD techniques on Pt-based al-loys ° observed hd metal dissolution, diffusion of 3bulk oxides on the surface, and migration and agglomeration of Pt. Yu et al. compared the durability and activity of PtCo/C with Pt/C catalysts. Throngh determination of the electrochemically active sniiace area, mass, and specific activities with respeet to the potential cycles, they found the overall cell performance of PtCo/C is higher than that of Pt/C. They also concluded that the observed dissolution of Co has no severe impact on the cell performanee or membrane conductance. Additionally, Popov et al studied the stabihty of Pt M/C for X = 1,3 and M = V, Fe, Ni, Co. ADT analyses revealed that Pt/C has the lowest activity when eompared to Pt-alloy catalysts, and that the metal dissolntion is lower for a Pt M ratio of 3 1 than compared to a 1 1 ratio. Also, Pt-Ni showed a lower dissolution rate than the other considered Pt-M alloys. 

In the U.S. regulatory emphasis at the present time is on in-use performance. The pre-production accelerated durability tests cannot fully duplicate the same distribution of performance as in-use vehicles. Large numbers of three-way catalysts introduced in 1981 and following years are now reaching 50,000 miles so that field performance can be evaluated. 

The usual approach to accelerated durability trials is either to make a simple comparison of materials or, by extrapolation, to predict performance at longer times under less severe conditions. 

Sodimn sulfate is known to be a salt that causes the worst crystallization decay on pwrous materials and has become widely used in accelerated durability testing 13 1. However, the sodium sulfate system is complicated, because under different conditions (temperature and relative humidity), it will form two stable phases (thenardite, Na2S04 and mirabilite, Na2S04 IOH2O) or one metastable phase (heptahydrate, Na2S04-7H20) i3] [39], Jhe... 

ADT accelerated degradation test or accelerated durability test... 

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. 

TABLE 10.2 Summary of Accelerated Durability Tests in the Literature... 

FIGURE 10.18 Fluoride emissions of CCMs during accelerated durability testing. (Repr mtediromlnt.J.Hydrogen Energy, 35, S. Mu. Accelerated durability tests of catalyst layers with various pore volumes for catalyst coated membranes applied in PEM fuel cells, 2872-2876, Copyright (2010), with permission from Elsevier.)... 

M. P. Rodgers, R. Agarwal, B. P. Pearman et al, 2009. Accelerated durability testing of perfluorosulfonic... 

S. Mu. 2010. Accelerated durability tests of catalyst layers with various pore volumes for catalyst coated membranes apphed in PEM fuel cells. 35 2872-2876. 

Accelerated Durability Assessment of Composite Structures. ICCM 14, San Diego, 2003... 

As an accelerated testing method, the OCV hold test plays an important role in accelerated durability tests [13-18]. The OCV hold test is believed to accelerate the chemical degradation of the membrane, which results in higher gas... 

Table 1 Surface energies (by the Owens-Wendt method) of two different SIGRACET gas diffusion layer (GDL) types before and after accelerated durability testing (different catalyst-coated membranes were used in the cells)...

There are three classes of ageing processes to be considered for accelerated durability tests of ERC composites ageing effects associated with (i) the matrix (ii) the fibre and (iii) changes at the fibre-matrix interface. 

W.R. Sharman and B.P. Vautier, Accelerated durability testing of autoclaved wood-fibre reinforced cement-sheet composites . Durability of Budding Mater. 3, 1986,... 

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