Targets durability

The stability of electrocatalysts for PEMFCs is increasingly a key topic as commercial applications become nearer. The DoE has set challenging near-term durability targets for fuel cell technology (automotive 5,000 h by 2010 stationary 40,000 h by 2011) and has detailed the contribution of the (cathode) catalyst to these. In particular, for automotive systems as well as steady-state stability, activity after simulated drive cycles and start-stop transients has been considered. In practice, both these treatments have been found to lead to severe degradation of the standard state-of-the-art Pt/C catalyst, as detailed next. 

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... 

Achieve DOE system durability target of 5,000 hours on reformate. 

Current results indicate operational issues for the fuel processor subsystem to meet the DOE durability target of 5000 hours due to carbon formation and catalyst surface area. Upon post-analysis of the fuel processor, carbon formation was observed regardless... 

The main bottleneck now, if one wants to shorten the time to market for new PEMFCs, is that one needs an efficient method to take into account durability targets in all R D actions on components and unit operating management strategies. A simple try and error method is manageable to get system durability from a few hundreds to a few thousands of hours. It is practically impossible when one wants to get from a few thousands of hours up to several tens of thousands of hours. 

In conclusion, all of these observations indicate that there is still much room to improve ADAFC performance by developing novel materials and, on the other hand, by optimizing the operational conditions of the fuel cell. Future work should look into a wider range of potential low-cost materials and composites with novel structures and properties, presenting catalytic activity comparable to that of noble metals. The development of new catalyst systems is more likely in alkaline media because of the wide range of options for the materials support and catalyst, as compared to acidic media which offer more limited materials choice. Moreover, efforts have to be addressed to meet the durability targets required for commercial application. More work is needed to optimize the operational fuel cell conditions, by achieving suitable chemical (OH concentration, hydroxyl/alcohol ratio in the fuel stream) and physical (temperature, pressure, flow rate) parameters. 

Lithium-ion batteries are electrochemical systems whose processes are related to temperature higher temperatures accelerate side reactions which cause a reduction of battery capacity or an increase in battery resistance. Long-term exposure to temperature values above 32 °C should be minimized to meet a 10-year durability target (see Figure 8.16). Each specific battery chemistry has a different sensitivity, but the general rule applies to all systems. 

In this section, the operational modes that fuel cell stacks are subjected to the 2015 performance, cost, and durability targets that fuel cell technology must achieve and recent advancements made by automotive companies toward achieving the targets for commercialization are discussed. 

The required durability target of HT-PEMFC systems differs for APU and CHP applications. For the APU application, the systems need to satisfy the durability target of 20,000 h with the degradation rate of 1 %/1000 h by 2015 [4]. The APU systems need to operate in the mode of daily cycles to stand-by condition and weekly cycles to off condition [4]. For the micro-CHP in the power range of 1-10 kW, the lifetime of... 

Table 22.1 DOE durability targets for PEMFCs for automotive and stationary systems, power units, stacks, and components, updated 2014 [11]...

In pursuit of this strategy, a European Hydrogen and Fuel Cell Platform was created. On this platform, specific research targets related to lower costs and higher durability were formulated for PEMFCs, PAFCs, MCFCs, and SOFCs as the major fuel cell varieties. The cost limit for a fuel cell stack was fixed at 200 to 500/kW, the cost limit for the entire power system at 1000 to 1500/kW. The durability target was set at 20,000 to 40,000 hours. It must be pointed out that... 

In this chapter, we attempt to evaluate state-of-the-art commercial conventional-carbon-support MEAs for their carbon corrosion kinetics, the relationship between cell voltage loss and carbon-support weight loss, and the fife projection of the catalyst support under automotive operating conditions. These operational conditions include steady-state operation, transient, start/stop, and unintended deviations from nominal run parameters. On the basis of these analyses, we elucidate (1) which operational conditions result in severe carbon corrosion, (2) whether current conventional-carbon-support MEAs are robust enough to meet automotive durability targets, and (3) if a state-of-the-art corrosion-resistant carbon-support MEA is absolutely required for improving automotive fuel cell durability. 

Carbon corrosion kinetics of commercial conventional-carbon-supported MEAs were studied at various potmtials and tempoalures. The lifetime projectiMi of OMventional-carbon-supported MEAs in the automotive fuel cell system was then analyzed using the kinetics shown in this chapto. It is found that these conventional-carbon-supported MEAs are not likely to meet automotive fuel cell durability targets under the severely dynamic automotive operational conditions. Automotive fuel cell systan start/stop and local anode starvation are beheved to be two of the rntgor contributors... 

The cell and stack level is an intermediate stage between the component-based analysis and the system level. On the way to the durability targets of 5,000h for automotive applications, as formulated by the US DOE for 2010/2015, or the Japanese NEDO s lifetime targets for stationary applications of40,000 and 90,000h in 2010 and 2015, respectively, investigations on a techrtical cell level are required. 

Durability Targets for Stationary and Automotive Applications in Japan... 

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