Behavior of water below the freezing point in PEFCs

Ishikawa, Yuji; Morita, Touru; Nakata, Keiichi; Yoshida, Kiyohide; Shiozawa, Masahiro

doi:10.1016/j.jpowsour.2006.08.026

Cited by 121 publications

(104 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The produced water at the -10 °C cold start reaches the interface between the catalyst layer and the MPL where it remains as a supercooled liquid water film for some time before it freezes, (Fig. 9(b)), this is a reason why the released heat of solidification due to the freezing can be detected by infrared thermography [10][11][12]. The freezing at the interface triggers the operation shutdown, and in total the freezing mechanism and cold start characteristics differ, depending on whether supercooled water can exist in a cell.…”

Section: Observation Of Ice Distribution and Evaluation Of The Freezimentioning

confidence: 99%

“…Recently, cryo-SEM observations were conducted to elucidate further details of the ice distribution in the catalyst layer at -25 °C or -20 °C; these observations were carried out with the examined components kept at very low temperature and in vacuum conditions to avoid thawing and covering by frost deposits [6][7][8][9]. At temperatures closer to zero, like -10 °C, it was reported that the produced water is present in a supercooled state, and that the freezing behavior in a PEFC can be visualized by infrared thermography and it was possible to capture the 2-dimensional propagation in the high temperature region caused by the release of heat due to freezing [10][11][12]. Thus, the characteristics of the cold start using specific cells and start-up temperatures, and the effects of the water freezing in the cell on the performance deterioration have been reported.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cold start characteristics and freezing mechanism dependence on start-up temperature in a polymer electrolyte membrane fuel cell

Tabe

Saito

Fukui

et al. 2012

Journal of Power Sources

126

View full text Add to dashboard Cite

Cold start characteristics of a polymer electrolyte membrane fuel cell are investigated experimentally, and microscopic observations are conducted to clarify the freezing mechanism in the cell. The results show that the freezing mechanism can be classified into two types: freezing in the cathode catalyst layer at very low temperature like −20 °C, and freezing due to supercooled water at the interface between the catalyst layer and the gas diffusion layer near 0 °C like −10 °C. The amount of water produced during the cold start is related to the initial wetness condition of the polymer electrolyte membrane, because water absorption by the membrane due to back diffusion plays an important role to prevent the water from freezing. It is also shown that after the shutdown of the cold start the cell performance of a subsequent operation at 30 °C is temporarily deteriorated after the freezing at −10 °C, but not after the freezing at −20 °C. The ice formed at the interface between the catalyst layer and the gas diffusion layer is estimated to cause the temporary deterioration, and the function of a micro porous layer coating the gas diffusion layer for the ice formation is also discussed. Highlights• Two freezing types at cold start in and on the surface of a cathode catalyst layer • Direct observation of the ice formed on the catalyst layer surface • Temporary performance deterioration at 30 °C caused by ice on the surface

show abstract

Section: Observation Of Ice Distribution and Evaluation Of The Freezimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cold start characteristics and freezing mechanism dependence on start-up temperature in a polymer electrolyte membrane fuel cell

Tabe

Saito

Fukui

et al. 2012

Journal of Power Sources

126

View full text Add to dashboard Cite

show abstract

“…This suggests that the freezing-point depression of water in the catalyst is no more than 2˚C. The generation of liquid water below 0˚C was again witnessed in [289,290] but the temperature of water freezing was even lower (e.g. -10˚C in [298]).…”

Section: Ice Formationmentioning

confidence: 99%

“…-10˚C in [298]). Ishikawa et al [289] attributed the reason for this low temperature to the freezing phenomenon of the super-cooled generated water where heat of solidification is emitted and the temperature rises to 0˚C.…”

Section: Ice Formationmentioning

confidence: 99%

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

Ous

Arcoumanis

2013

Journal of Power Sources

133

View full text Add to dashboard Cite

This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThis review paper summarises the key aspects of Proton Exchange Membrane Fuel Cell (PEMFC) degradation that are associated with water formation, retention, accumulation, and transport mechanisms within the cell. Issues related to loss of active surface area of the catalyst, ionomer dissolution, membrane swelling, ice formation, corrosion, and contamination are also addressed and discussed. The impact of each of these water mechanisms on cell performance and durability was found to be different and to vary according to the design of the cell and its operating conditions. For example, the presence of liquid water within Membrane Electrode Assembly (MEA), as a result of water accumulation, can be detrimental if the operating temperature of the cell drops to sub-freezing.The volume expansion of liquid water due to ice formation can damage the morphology of different parts of the cell and may shorten its life-time. This can be more serious, for example, during the water transport mechanism where migration of Pt particles from the catalyst may take place after detachment from the carbon support. Furthermore, the effect of transport mechanism could be augmented if humid reactant gases containing impurities poison the membrane, leading to the same outcome as water retention or accumulation.Overall, the impact of water mechanisms can be classified as aging or catastrophic. Aging has a longterm impact over the duration of the PEMFC life-time whereas in the catastrophic mechanism the impact is immediate. The conversion of cell residual water into ice at sub-freezing temperatures by the water retention/ accumulation mechanism and the access of poisoning contaminants through the water transport mechanism are considered to fall into the catastrophic category. The effect of water mechanisms on PEMFC degradation can be reduced or even eliminated by (a) using advanced materials for improving the electrical, chemical and mechanical stability of the cell components against deterioration, and (b) implementing effective strategies for water management in the cell.

show abstract

“…The results there indicate that the ice formation at the interface between the gas diffusion layer (GDL) and the membrane electrode assembly (MEA) limits the diffusion of air to the reaction zone, resulting in the decreases in performance. The surface of the catalyst layer (CL) was also observed by visible light and infrared images at -10°C cold starting, showing water to be in a super-cooled state at the catalyst surface at -10°C [5]. Ge et al investigated the ice formation in the catalyst layer by cyclic voltammetry [6].…”

Section: Introductionmentioning

confidence: 99%