Durability testing fuel

Y. Yamamasu, T. Kakihara, E. Kasai, T. Morita, IHI, "Component Development and Durability Test of MCFC," in The International Fuel Cell Conference Proceedings, NEDO/MITI, Tokyo, Japan, Pgs. 161-164, 1992. 

Once the durability testing of the fuel cells is finalized, the internal components are then characterized. For diffusion layers, some of these characterization techniques include SEM to visualize surface changes, porosimetry measurements to analyze any changes in porosity within the DL and MPL, IGC (inverse gas chromatography) to identify relative humidity effects on the hydrophobic properties of the DLs, contact angle measurements to observe any changes in the hydrophobic/hydrophilic coatings of the DL, etc. [254,255]. 

Current efforts are focusing on optimizing the carbon monoxide removal reactor and developing a system prototype using commercially available pumps, blowers, fuel cells, valves, and controllers.In addition, durability testing along with thermal cycling needs to be done. 

Platinum-based catalysts are widely used in low-temperature fuel cells, so that up to 40% of the elementary fuel cell cost may come from platinum, making fuel cells expensive. The most electroreactive fuel is, of course, hydrogen, as in an acidic medium. Nickel-based compounds were used as catalysts in order to replace platinum for the electrochemical oxidation of hydrogen [66, 67]. Raney Ni catalysts appeared among the most active non-noble metals for the anode reaction in gas diffusion electrodes. However, the catalytic activity and stability of Raney Ni alone as a base metal for this reaction are limited. Indeed, Kiros and Schwartz [67] carried out durability tests with Ni and Pt-Pd gas diffusion electrodes in 6 M KOH medium and showed increased stability for the Pt-Pd-based catalysts compared with Raney Ni at a constant load of 100 mA cm and at temperatures close to 60 °C. Moreover, higher activity and stability could be achieved by doping Ni-Al alloys with a few percent of transition metals, such as Ti, Cr, Fe and Mo [68-70]. 

Separate Accelerated Stress Test (AST) protocols have been proposed by the US Department of Energy to assess the durability of fuel cell under conditions that promote distinct degradation modes... 

Debe, M.K., Steinbach, A.J., and Noda, K., Stop-start and high-current durability testing of nanostructured thin film catalysts for PEM fuel cells, ECS Trans., 3, 835, 2006. 

In the tests using lean-bum gasoline engines, the sensor emf correlated fairly well to the NO concentration measured by an independent NO analyzer in the range of engine rotation between 1000 and 2600 rpm. An accuracy of the sensor output in the engine rotation was 4 ppm at 45 ppm, NO 11 ppm at 101 ppm, and 11 ppm at 306 ppm, respectively, when calculated as NO concentrations. It means that the total error of measurement was no more than 10%. In another test it was confirmed that the sensor had enough durability for fuel-rich gas (A/F = 12) [35]. 

The catal ic properties were evaluated at the exhaust of a lean-burn S.I. engine (1350 cm displacement, air/fuel mass ratio A/F=18, 2000 rpm, 17 kW), in temperature programmed tests (from room temperature to 550°C), and isothermal durability tests (400 °C). Some tests were performed after water removal by a cold trap before feeding the reactor. 

The vehicle durability tests have consistently shown that substantial catalyst deactivation takes place with fuel at 10 mg/1 Pb. Lead levels of 3 mg/1 and below allow catalyst systems to function satisfactorily during 80K km of AMA drive cycle which would indicate that even if a customer continually drives at low speed (which gives max lead deposition condition) then catalyst deterioration due to lead will be minimal. The test results indicate that the effect of lead on the HEGO sensor is more critical than its 6ffect on the catalyst. 

Fuel flexibility of the fuel reforming subsystem was demonstrated using methane, propane, butane, methanol, ethanol, isooctane, and benchmark gasoline. A 1000-hour catalyst and reactor durability test was completed using benchmark gasoline. Warm transient response of less than 5 seconds was achieved for 10 to 90% of full reformer capacity. A three-fold increase in reformer productivity was achieved compared to the previous year, due to improved catalyst performance and more uniform flow within the reactor. Reactor concepts that would meet FreedomCAR s rapid start-up targets were developed. 

In the following sections we will discuss the most common durability tests and the different factors that lead to the power decrease of the fuel cell. Some of them are general to hydrogen-fed PEM fuel cells, while others are specific of DAFC. Kim and Zelenay [85] quoted that performance degradation of DMFC has received little attention compared with the degradation of H2/air PEM fuel cells systems, probably because lifetime requirements for DMFC systems are generally perceived as less stringent, and have not been defined as precisely as for fuel cells... 

A controlled porosity is of significant importance in fuel cell applications, since mass transport of the reactants to and the products away from the catalytically active sites plays an essential role in the device performance. It has been observed that the structural collapse of the electrode during durability tests impacts the performance of the fuel cell even more than the loss of active platinum particles [11], In addition to the tailored properties, which can be achieved by rational design of the template, another advantage is that the synthesis route is comparatively simple and not too expensive to be developed to industrial scale. 

Kundu S, Fowler M, Simona L and AbouataUah R (2008), Reversible and irreversible degradation in fuel cells during Open Circuit Voltage durability testing. Journal of Power Sources, 182,254-258. 

On the basis of the performances of various types of ADAFCs, the most relevant observation is the mandatory presence of OH ions in the fuel stream. Up to date, in the absence of OH in the alcohol solution, the cell performance is very poor and far from a possible industrial application. The addition of MOH into alcohol supply, however, is not desirable for different reasons, such as corrosion, electrode weeping, mechanic electrode destruction by carbonate crystals, and catalyst decomposition [145]. Therefore, in addition to short-time tests, durability tests on ADAFCs fuelled with alcohol -I- MOH in the presence of CO2 have to be carried out, to find a MOH content, resulting in a good compromise between the positive effect on cell performance and the negative effect on the durability. 

Since both activity measurements and durability tests done by RDE in a liquid electrochemical cell at room temperature do not necessarily reproduce the conditions in a fuel ceU, one should use RDE only as a screening test. Fuel cell testing of new catalysts should be pursued as early as possible in its development stage. Because fuel cell tests often require much labor and capital investment and are not readily available to all researchers, more collaboration between labs is encouraged. 

Pors et al. [37] presented different, stepwise improved fuel injection systems as part of the diesel ATR development of Jiilich research center. While air was mixed with the fuel and steam added downstream in the ATR-5 reactor (Figure 14.2a), superheated steam was mixed with the fuel, which was dispersed in an atomization nozzle in ATR-7 and the air added downstream. Further improvement by adding a cyclone-like separation of nonevaporated residues in ATR-8 (Figure 14.2b) led to an increased durability of the injection system, which was proven experimentally by a 1000 h durability test. Later Pasel et al. [40] reported 2000 h durability of the ATR-8 reactor for Jet-Al aviation fuel. 

Wichert, M, Men, Y, O Connell, M, Tiemann, D, Zapf, R, Kolb, G, Butschek, S, Frank, R, Schiegl, A. Self-sustained operation and durability test of a 300 W-class micro-structured LPG fuel processor. Int. J. Hydrog. Energy 2011 36 3496-3504. 

A. (2011) Self-sustained operation and durability test of a 300W-class micro-structured LPG fuel processor. fnt. J. Hydrogen Energy, 36, 3496-3504. 

Electrode Catalysts for Direct Methanol Fuel Cells, Fig. 9 Changes in MOR activities of Pt-Ru catalysts synthesized with and without addition of D J -tartaric acid by potential cycling durability test... 

During S-cell stack performance test, the reformed gas with 6,820 seem flow rate and air with 13,000 seem rate were respectively used as fuel and oxidizer gas to complete l-V-P and durability tests. The reformed gas generated from methane and water vapor through the home-made reformer installed in the SOFC measurement system. According to our experiences about measuring the degradation rate of SOFC MSC cell stack, the most suitable applied current density is located around 400 mA/cm at 700 C. So, the constant current density is kept at 400 mA/cm in long term durability test. 

Wood D, Davey J, Garzon E, Atanassov P, Borup R (2005) Mass-transport phenomena and long-term performance limitations in H2-air PEMEC durability testing, 2005 fuel cell seminar abstracts, 14-11-2005 Courtesy Associates, Washington... 

Illustrated by the previously discussed durability tests, p-PBI MEAs have been shown to be physically and chemically robust. Highly resistant to fuel... 

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