A mathematical model is developed to describe the reaction dynamics in the vicinity of the triple-phase boundary (TPB), which is an important part of the pore scale structure of the catalyst layer in proton exchange membrane fuel cells. The model incorporates coupled diffusion, migration, and reaction phenomena of the chemical components in an undersaturated air pore and ionomer. One challenging feature of the work is the description of the TPB by a system of nonlinear partial differential equations (PDEs), coupling bulk, and surface-diffusion phenomena, which offers an approach to study the rarely investigated proton surface diffusion along the air pore surface. A numerical technique is implemented, taking into account the particular form of the domain, in order to solve the nonlinear PDE system efficiently. Several numerical results are discussed, including a sensitivity analysis with respect to the physical reference case and geometric parameters. The results indicate that surface diffusion might play a major role for the reaction kinetics, but only if the air pore is void of liquid water. In contrast, the formation of liquid water in the gas pores will turn surface diffusion into bulk diffusion, with the latter resembling the Grotthus mechanism.

1.
Wang
,
Q.
,
Eikerling
,
M.
,
Song
,
D.
, and
Liu
,
Z.
, 2004, “
Structure and Performance of Different Types of Agglomerates in Cathode Catalyst Layers of PEM Fuel Cells
,”
J. Electroanal. Chem.
0022-0728,
573
, pp.
61
69
.
2.
Berg
,
P.
,
Novruzi
,
A.
, and
Promislow
,
K.
, 2006, “
Analysis of a Cathode Catalyst Layer Model for a Polymer Electrolyte Fuel Cell
,”
Chem. Eng. Sci.
0009-2509,
61
, pp.
4316
4331
.
3.
Eikerling
,
M.
, 2006, “
Water Management in Cathode Catalyst Layers of PEM Fuel Cells: A Structure-Based Model
,”
J. Electrochem. Soc.
0013-4651,
153
, pp.
E58
E70
.
4.
Song
,
D.
,
Wang
,
Q.
,
Liu
,
Z.
,
Navessin
,
T.
,
Eikerling
,
M.
, and
Holdcroft
,
S.
, 2004, “
Numerical Optimization Study of Catalyst Layer for PEM Fuel Cell Cathode
,”
J. Power Sources
0378-7753,
126
, pp.
104
111
.
5.
O’Hayre
,
R.
,
Barnett
,
D. M.
, and
Prinz
,
F. B.
, 2005, “
The Triple Phase Boundary: A Mathematical Model and Experimental Investigations for Fuel Cells
,”
J. Electrochem. Soc.
0013-4651,
152
, pp.
439
444
.
6.
Pisani
,
L.
,
Valentinin
,
M.
, and
Murgia
,
G.
, 2003, “
Analytical Pore Scale Modeling of the Reactive Region of Polymer Electrolyte Fuel Cells
,”
J. Electrochem. Soc.
0013-4651,
150
, pp.
A1549
A1559
.
7.
Ge
,
S.
,
Li
,
X.
,
Yi
,
B.
, and
Hsinga
,
I. M.
, 2005, “
Absorption, Desorption, and Transport of Water in Polymer Electrolyte Membranes for Fuel Cells
,”
J. Electrochem. Soc.
0013-4651,
152
, pp.
1149
1157
.
8.
Berg
,
P.
,
Promislow
,
K.
,
St. Pierre
,
J.
,
Stumper
,
J.
, and
Wetton
,
B.
, 2004, “
Water Management in PEM Fuel Cells
,”
J. Electrochem. Soc.
0013-4651,
151
, pp.
341
353
.
9.
Weber
,
A. Z.
, and
Newman
,
J.
, 2004, “
Transport in Polymer-Electrolyte Membranes II: Mathematical Model
,”
J. Electrochem. Soc.
0013-4651,
151
, pp.
311
325
.
10.
Bothe
,
D.
,
Koebe
,
M.
,
Wielage
,
K.
,
Prüss
,
J.
, and
Warnecke
,
H. J.
, 2004, “
Direct Numerical Simulation of Mass Transfer Between Rising Gas Bubbles and Water
,”
Bubbly Flows: Analysis, Modelling and Calculation
,
M.
Sommerfeld
, ed.,
Springer
,
Berlin
, pp.
159
174
.
11.
Haug
,
A. T.
, and
White
,
R. E.
, 2000, “
Oxygen Diffusion Coefficient and Solubility in a New Proton Exchange Membrane
,”
J. Electrochem. Soc.
0013-4651,
147
, pp.
980
983
.
12.
Lehtinen
,
T.
,
Sundholm
,
G.
,
Holmberg
,
S.
,
Sundholm
,
F.
,
Bjornbom
,
P.
, and
Bursell
,
M.
, 1998, “
Electrochemical Characterization of PVDF-Based Proton Conducting Membranes for Fuel Cells
,”
Electrochim. Acta
0013-4686,
43
, pp.
1881
1890
.
13.
Zawodzinski
,
T.
,
Derouin
,
C.
,
Radzinski
,
S.
,
Sherman
,
R.
,
Smith
,
V.
,
Springer
,
T.
, and
Gottesfeld
,
S.
, 1993, “
A Comparative Study of Water Uptake by and Transport Through Ionomeric Fuel Cell Membranes
,”
J. Electrochem. Soc.
0013-4651,
140
, pp.
1041
1047
.
You do not currently have access to this content.