Carbon electrodes are one of the key materials in polymer electrolyte fuel cells (PEFC), or proton exchange membrane fuel cells (PEMFC). The electrodes should allow water or water vapor, which is produced by the redox reactions, to flow out of the cells efficiently. In the meantime, the catalysis reactions are not interfered. In this study, the carbon electrodes for PEMFC have been modified in terms of the hydrophobic and hydrophilic properties by plasma irradiation. The process utilized inductively coupled plasma (ICP) driven by applying radio frequency (rf) power on an induction coil. A pure Ar, $O2$, and $Ar∕O2$ gas mixture were used as the plasma gas. Only one side of the sample has been treated. The material properties of the plasma treated and untreated carbon electrodes were investigated by Raman spectroscopy, Fourier transformed infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). FTIR results show the plasma treatments effectively modified the functional groups on the carbon surface, and therefore the hydrophilic and hydrophobic properties of the surface. SEM and Raman spectra data suggested that the ion bombardment during plasma treatments alters the surface morphology and carbon bonding structures of the samples, which also result in a hydrophilic surface. The treated carbon electrodes were used as cathodes and have been packed with commercial carbon anodes and catalyst coated membrane to form $5cm×5cm$ fuel cells. The current-voltage polarization curves of these fuel cells were measured and compared. The test results show the feasibility of improving the cell performance by plasma treated electrodes. The feasibility of altering the hydrophobic and hydrophilic properties by plasma treatment has been demonstrated. The capillary effect due to the unbalanced hydrophilicity between the treated and untreated electrode surfaces may be responsible for the improved cell performance.

1.
Springer
,
T. E.
,
Zawodzinski
,
T. A.
, and
Gottesfeld
,
S.
, 1991, “
Polymer Electrolyte Fuel Cell Model
,”
J. Electrochem. Soc.
0013-4651,
138
, pp.
2334
2341
.
2.
Mench
,
M. M.
, and
Wang
,
C. Y.
, 2003, “
An In Situ Method for Determination of Current Distribution in PEM Fuel Cells Applied to a Direct Methanol Fuel Cell
,”
J. Electrochem. Soc.
0013-4651,
150
, pp.
79
85
.
3.
Lu
,
G. Q.
, and
Wang
,
C. Y.
, 2004, “
Electrochemical and Flow Characterization of a Direct Methanol Cuel Cell
,”
J. Power Sources
0378-7753,
134
, pp.
33
40
.
4.
Jordan
,
L. R.
,
Shukla
,
A.
,
Behrsing
,
K. T.
,
Avery
,
N. R.
,
Muddle
,
B. C.
, and
Forsyth
,
M.
, 2000, “
Diffusion Layer Parameters Influencing Optimal Fuel Cell Performance
,”
J. Power Sources
0378-7753,
86
, pp.
250
254
.
5.
Chiu
,
K.-F.
, and
Barber
,
Z. H.
, 2002, “
Characterization of Inductively Coupled Plasma in the Ionized Physical Vapor Deposition System
,”
J. Appl. Phys.
0021-8979,
91
, pp.
1797
1803
.
6.
Smith
,
D. L.
, 1995,
Thin Film Deposition—Principles and Practice
,
McGraw-Hill
,
New York
, Chap. 8.
7.
Fukunaga
,
A.
,
Komami
,
T.
,
Ueda
,
S.
, and
Nagumo
,
M.
, 1999, “
Plasma Treatment of Pitch-based Ultra High Modulus Carbon Fibers
,”
Carbon
0008-6223,
37
, pp.
1087
1091
.
8.
Baranauskas
,
V.
,
Peterlevitz
,
A. C.
,
Ceragioli
,
H. J.
, and
Durrant
,
S. F.
, 2002, “
Growth of Glassy Carbon on Natural Fibers
,”
J. Non-Cryst. Solids
0022-3093,
304
, pp.
271
277
.
9.
Katoh
,
M.
,
Izumi
,
Y.
,
Kimura
,
H.
,
Ohte
,
T.
,
Kojima
,
A.
, and
Ohtani
,
S.
, 1996, “
Investigation of Characteristic of Carbon Materials with Various Structures Modified by Plasma Using plasma Diagnostics and Material-Surface Analysis
,”
Appl. Surf. Sci.
0169-4332,
100∕101
, pp.
226
231
.
10.
Kinugasa
,
S.
,
Tanabe
,
K.
, and
Tamura
,
T.
, “
Spectral Database for Organic Compounds, SDBS
,” http://www.aist.go.jp/RIODB/SDBS/cgi-bin/cre_index.cgihttp://www.aist.go.jp/RIODB/SDBS/cgi-bin/cre_index.cgi.