Investigation of the recoverable degradation of PEM fuel cell operated under drive cycle and different humidities

Wang, Feijie; Yang, Daijun; Li, Bing; Zhang, Hao; Hao, Chuanpu; Chang, Fengrui; Ma, Jie

doi:10.1016/j.ijhydene.2014.02.023

Cited by 36 publications

(11 citation statements)

References 28 publications

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“…For automotive fuel cells, typical is degradation of the catalyst layer (CL) caused by carbon corrosion due to frequent starts and stops, loss of catalyst active area caused by platinum (Pt) dissolution and sintering due to frequent voltage cycling, loss of catalyst active area due to adsorption of contaminants from the inlet gases, and/or mechanical degradation due to thermal and humidity cycling induced by the load profile as well as by the environment in which the vehicle operates . However, when the fuel cell exploitation or its durability testing is interrupted due to certain reason, such as equipment maintenance, startup/shutdown procedure, overnight rest, continuous electrochemical in situ testing, etc., a phenomenon of performance recovery could occur, and it has been reported in handful of studies . Therefore, some degradation may be recoverable, also called temporary, reversible, regenerative, restorable, or transient performance degradation.…”

Section: Introductionmentioning

confidence: 99%

Impact of Shutdown Procedures on Recovery Phenomena of Proton Exchange Membrane Fuel Cells

Pivac

Barbir

2020

Fuel Cells

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The paper presents the obtained measurement and analysis results of the accelerated stress test protocols consisting of voltage cycling, designed to target electrocatalyst degradation, with the intentional recovery periods (so-called soak time steps) every 2,500 voltage cycles on an already conditioned 50 cm 2 (single) fuel cell provided by ElringKlinger. Before and after every intentional stop, a series of diagnostic methods (polarization curves, electrochemical impedance spectroscopy, cyclic voltammetry, linear sweep voltammetry) were performed. During the conducted durability test, different shutdown procedures, as well as different duration of the soak time period were tested with their impact on perfor-mance recovery phenomenon. The results suggest that cause of the reversible degradation could be accumulated water within the cell and/or presence of oxygen within the catalyst layer leading to formation of platinum oxides on the catalyst surface. The prolonged soak time step reduces recovery effect, while rapid reduction of the cell temperature with ice proved to be counterproductive for performance recovery. Shutdown procedure without shortly-connected resistor has shown no effect on recovery. Shutdown procedure without nitrogen purge proved to be the most effective for performance recovery.

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Section: Introductionmentioning

confidence: 99%

Impact of Shutdown Procedures on Recovery Phenomena of Proton Exchange Membrane Fuel Cells

Pivac

Barbir

2020

Fuel Cells

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“…influence the degradation of the components and reduce the lifetime of the device. Numerous publications have investigated different aspects of degradation and their mitigation . In particular, degradation of the polymer can be generated by mechanical and chemical stress .…”

Section: Introductionmentioning

confidence: 99%

Influence of Water and Temperature on Ionomer in Catalytic Layers and Membranes of Fuel Cells and Electrolyzers Evaluated by AFM

et al. 2018

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The major difference for the durability of the materials in PEM fuel cells and PEM electrolyzers is the exposure to humidified gases and to liquid water, respectively. Aquivion and Nafion ionomer was investigated at surfaces of membranes and cross‐sections of electrodes by material‐sensitive atomic force microscopy. The dimensional behavior of electrodes and membranes in a membrane‐electrode assembly cross section was studied as a function of combined humidity and temperature changes. The observed opposite effects of ionomer dimensional changes in membrane and catalytic layers are important for understanding mechanical stress factors and degradation. For the lamellar polymer phase at moderate humidity, a linear swelling behavior and the enclosure of multiples of 0.8 nm‐thick water layers was observed. Submersed in water, 3 nm‐thick enclosed water layers were found. At the water‐immersed Aquivion membrane derived from alcoholic dispersion larger 30–50 nm sized water‐rich areas were found. In contrast, for membranes derived from water‐based dispersion the water‐rich phase was smaller with 11 nm. The thickness of the ultrathin ionomer layers in the electrode was investigated as a function of humidity and temperature. A linear swelling was found for humidity changes whereas nonlinear behavior with 100% expansion and hysteresis was seen for temperature cycles.

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“…[21][22][23] The reversible voltage decays are often higher than the irreversible ones 21,24 and may develop into irreversible ones over time, 25,26 thus necessitating proper recovery protocols at the right intervals. In the literature, one may find various recovery procedures aimed at mitigating different reversible losses, including steps like shutdown/interruption, 22,23,27 increasing gas humidity, [28][29][30] lowering the cell potential, [28][29][30][31] and switching the cathode gas to N 2 , 28,32,33 to name a few.…”

mentioning

confidence: 99%

Effects of PEMFC Operational History under Dry/Wet Conditions on Additional Voltage Losses due to Ionomer Migration

Đào

Peitl

et al. 2020

J. Electrochem. Soc.

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Over its lifetime in a fuel cell electric vehicle, a polymer electrolyte membrane fuel cell inevitably suffers from certain duration of dry operational conditions, where significant performance losses of the fuel cell take place. In this study, we investigate the activity changes of the fuel cell after a prolonged degradation protocol under dry operational condition, followed by various recovery procedures under wet conditions. The utilization of diluted air on the cathode side is found to be advantageous for the recovery due to the superior heat and water management. This more efficient recovery protocol allows the deconvolution of reversible and irreversible voltages losses after dry operations. A subsequent mechanistic study reveals an irreversible decrease of the effective ionomer coverage on the catalyst particles, while the proton conductivity of the catalyst layer drops. These observations point towards ionomer structural changes caused by the dry conditions. This is confirmed by post-mortem analysis via scanning electron microscope, showing clearly that ionomer redistributes and migrates, an additional mechanism which leads to the performance losses. Overall, the degradation mechanisms seem to be mitigated by higher ionomer content in the catalyst layer, while the investigated surface modification of carbon support shows minor sensitivities.

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Investigation of the recoverable degradation of PEM fuel cell operated under drive cycle and different humidities

Cited by 36 publications

References 28 publications

Impact of Shutdown Procedures on Recovery Phenomena of Proton Exchange Membrane Fuel Cells

Impact of Shutdown Procedures on Recovery Phenomena of Proton Exchange Membrane Fuel Cells

Influence of Water and Temperature on Ionomer in Catalytic Layers and Membranes of Fuel Cells and Electrolyzers Evaluated by AFM

Effects of PEMFC Operational History under Dry/Wet Conditions on Additional Voltage Losses due to Ionomer Migration

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