Water transport in PEFC cold startup withtemperature rise simulating adiabatic condition〇 Ken Hirai and Yutaka Tabe
Division of Energy and Environmental Systems, Hokkaido University, Japan

1. Introductione-e-O₂

H2H+Catalyst
Layer

Membrane

CatalystLayer

2. Model analysis proceduremosmλclλmen

Anode Catalyst Layer

mgenmdif

Membrane
Cathode Catalyst Layer

Water generation

Model analysis• Estimate water contentin membrane• Determine dry-out
condition at -30˚C

Objective
H₂OImprove cold start characteristics withtemperature rise from -30˚CGDL

H2GDLApproach

Problems in the cold startup of PEFC
• Shutdown due to ice formation(CL, interface between CL and MPL)
• Dry-out at dry and very lowtemperature (membrane)

3. Experimental procedure

Simple assumption• One-dimensional model• Considering water transport inmembrane and cathode catalyst
layermgen = 2F 𝑀𝑤𝑎𝑡𝑒𝑟Electro-osmosis mosm =𝛽𝜆F

𝑀𝑤𝑎𝑡𝑒𝑟

Cooling
1~2hours

Cold startup• Constant current density• Initial temperature : -30˚C

Apparatus of simulating adiabatic condition
Assumption
In adiabatic condition,
cell temperature rises withreaction heat.

∂𝜆𝑐𝑙 −mdif +mosm +𝑚𝑔𝑒𝑛 A=∂t𝑀𝑤𝑎𝑡𝑒𝑟𝑠𝑐𝑙∂λ15.
Back diffusion mdif =ρ𝑚𝑒𝑚ε 𝐷λ 𝑀𝑤𝑎𝑡𝑒𝑟∂yWet purge
3hoursAging5hours∂𝜆𝑚𝑒𝑚 mdif −𝑚𝑜𝑠𝑚 A=∂t𝑀𝑤𝑎𝑡𝑒𝑟 𝑠𝑚𝑒𝑚

𝐼𝑂𝑅𝑅

𝐼𝐻 +Experiment• Determine dry-out conditionat -30˚C• Cold startup simulating
adiabatic condition by heater

Proton conductivity of membrane[1]𝐸-52-3
κ =(−4.2263×10 λ +1.2631×10 λ−0.0023)exp

11−𝑅 243
𝑇Simulate adiabatic conditionof single cell with heaters[1] X. Wang et al., J. Power Sources 195 (2010) 6680-6687.

ExperimentCalculation

050

100 150
Time [sec]200250Experiment

0.20

Dry-out area

0.15
0.10
0.05

No dry-out area

0.00
0.0

2.0
4.0
6.0
8.0
Initial cell resistance [Ωcm2]

Dry-out condition

Parameter fitting corresponding toexperimental results of cell resistanceThreshold of dry-out
Resistance overvoltage 0.35V or above

20.07A/cm after 30sec

2 step loading : lower
resistance overvoltage

Resistanceovervoltage [V]

5. Experimental results and discussion(with temperature rise)
0.40
0.30
0.200.100.00

2step
Ramp

010Condition
Current density(A/cm2) 0.04→0.07 (after 30 sec)
Flow rate (sccm)
H2 : 348 Air : 829

2030
Time [sec]4050

Voltage [V]Resistance ×10-1 [Ωcm2]

Cell resistance transition

Target current density

Current density [A/cm2]

8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0

Current density [A/cm2]

Cell resistance [Ωcm2]

4. Results and discussion (dry-out)
Model analysis

Dry-out condition fits
experimental results

0.20

Dry-out
No dry-out
Dry-out condition
estimated by model

0.15
0.10
0.05
0.00
0.0

2.0
4.0
6.0
8.0
Initial cell resistance [Ωcm2]

Limitation of loading current density
corresponds to initial cell resistance.
1.2
Celltemperature

1.0
0.8
0.6

Cell voltage

0.4
0.2

Cell resistance

0.0
050

50-5-10-15-20-25-30

100 150 200 250 300 350
Time [sec]Cold startup from -30℃ without dry-out and ice formation

Conclusions

Future work

• Estimate dry-out condition at -30˚C with experiment and model analysis• Improve cold start characteristics from -30˚C with temperature rise
simulating adiabatic condition• Effect of MPL wettability and initial
temperature on dry-out condition• Method of simulating adiabatic condition¥

Temperature [℃]𝐸= −32.025λ3+619.76λ2−3770.2λ+10722𝑅¥