Durability acid loss

The suppression of acid loss can be a more challenging problem for improving the durability of HT-PEMFC MEA. The acid loss is caused by evaporation, compression pressure of stack, diffusion from MEA to flow field, and volume change caused by hydration of acid which can occur when exposed to highly humid environment. The retention of acid within the catalyst layer can be improved by adding materials that can either absorb acid [40] or form... 

This chapter is devoted to a review of material issues for HT-PEMFC components and is built on relevant evaluation of data from literature on membrane oxidation, acid loss, platinum dissolution, and carbon corrosion. Finally, the state-of-the-art durability of PBI-based fuel cells is summarized. For certain applications, like in mobile auxiliary power units exposed to severe vibrations and road dust or to maritime saline mists, the picture becomes more complicated and knowledge today is rather limited. 

Combination Flame Retardant—Durable Press Performance. Systems using THPC, urea, and TMM can be formulated to give fabrics which combine both flame-retardant performance and increased wrinkle recovery values (80). Another system employs dimethylol cyanoguanidine with THPC under acidic conditions (115). Both of these systems lead to substantial losses in fabric tensile and tearing strength. 

The stability and durability of Pt alloys, especially those involving a >d transition metal, are the major hurdles preventing them from commercial fuel cell applications. "" The transition metals in these alloys are not thermodynamically stable and may leach out in the acidic PEM fuel cell environment. Transition metal atoms at the surface of the alloy particles leach out faster than those under the surface of Pt atom layers." The metal cations of the leaching products can replace the protons of ionomers in the membrane and lead to reduced ionic conductivity, which in turn increases the resistance loss and activation overpotential loss. Gasteiger et al. showed that preleached Pt alloys displayed improved chemical stability and reduced ORR overpotential loss (in the mass transport region), but their long-term stability has not been demonstrated. " These alloys experienced rapid activity loss after a few hundred hours of fuel cell tests, which was attributed to changes in their surface composition and structure." ... 

Besides activity, durability of metal electrode nano-catalysts in acid medium has become one of the most important challenges of low-temperature fuel cell technologies. It has been reported that platinum electrode surface area loss significantly shortens the lifetime of fuel cells. In recent years, platinum-based alloys, used as cathode electrocatalysts, have been found to possess enhanced stability compared to pure Pt. The phenomenon is quite unusual, because alloy metals, such as Fe, Co and Ni, generally exhibit greater chemical and electrochemical activities than pure Pt. Some studies have revealed that the surface stmcture of these alloys differs considerably from that in the bulk A pure Pt-skin is formed in the outmost layer of the alloys due to surface segrega-... 

The pigment is a mixture of organic and inorganic compounds bonded by hydrogen that, in addition to its spectacular color, has an exceptional durability. The color still remains on a variety of Maya artifacts and architecture. It is resistant to natural acids, alkalis, solvents, heat, and vegetation. Maya blue is resistant to color loss after centuries in the tropical rainforest of the Maya heartland. 

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