Research Article
Experimental Investigation of a Direct Methanol Fuel Cell with
Hilbert Fractal Current Collectors
Jing-Yi Chang,
1
Yean-Der Kuan,
2
and Shi-Min Lee
3
1
Ho Tai Development Co., LTD., 12F., No. 143, Fuxing N. Road, Taipei 105, Taiwan
2
National Chin-Yi University of Technology, No. 35, Lane 215, Section 1, Chung-Shan Road, Taiping District, Taichung 411, Taiwan
3
Tamkang University, No. 151, Ying-Chuan Road, Tamsui District, New Taipei City 251, Taiwan
Correspondence should be addressed to Yean-Der Kuan; ydkuan@ncut.edu.tw
Received 21 February 2014; Revised 29 April 2014; Accepted 29 April 2014; Published 20 May 2014
Academic Editor: Lin Liu
Copyright © 2014 Jing-Yi Chang et al. Tis is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Te Hilbert curve is a continuous type of fractal space-flling curve. Tis fractal curve visits every point in a square grid with a size
of 2×2, 4×4, or any other power of two. Tis paper presents Hilbert fractal curve application to direct methanol fuel cell (DMFC)
current collectors. Te current collectors are carved following frst, second, and third order Hilbert fractal curves. Tese curves give
the current collectors diferent free open ratios and opening perimeters. We conducted an experimental investigation into DMFC
performance as a function of the free open ratio and opening perimeter on the bipolar plates. Nyquist plots of the bipolar plates
are made and compared using electrochemical impedance spectroscopy (EIS) experiments to understand the phenomena in depth.
Te results obtained in this paper could be a good reference for future current collector design.
1. Introduction
A fuel cell is an energy generator that converts chemical
energy stored in the fuel directly into electrical energy using a
series of electrochemical reactions without any moving parts.
Te fuel cell system is therefore simple and ideally noiseless.
Compared with a traditional combustion engine, the fuel cell
has the main advantages that it is clean, efcient, quiet, and
simple, with a power and capacity ratio that can be scaled
[1]. Te direct methanol fuel cell (DMFC) is a prominent
potential substitute power source for portable applications.
Te advantages of the DMFC are operating at near room
temperature, using methanol without a bulk transformer, and
using convenient combination liquid fuel storage and refuel-
ing system. Te DMFC is, therefore, suitable for miniature
designs and can be easily carried [2, 3].
A DMFC usually operates near room temperature. Te
anode, cathode, and overall reactions are
Anode: CH
3
OH + H
2
O → 6e
−
+6H
+
+ CO
2
(1)
Cathode:
3
2
O
2
+6e
−
+6H
+
→ 3H
2
O (2)
Overall: CH
3
OH +
3
2
O
2
→ 2H
2
O + CO
2
. (3)
Te anode reactants are methanol and water. Te oxida-
tion reaction occurs at the anode, which converts the reac-
tants into hydrogen protons, electrons, and carbon dioxide.
Te hydrogen protons are transported from the anode to
the cathode through a polymer electrolyte membrane. Te
electrons released at the anode are conducted through an
external circuit to the cathode. Te reduction reaction occurs
at the cathode to change protons, electrons, and oxygen into
water [4].
In a typical DMFC fuel cell, the bipolar plate is the unit
that carries electrons away from the anode to be received
at the cathode, distributes the fuel and oxidant within the
cell, separates the individual cells in the stack, and assists
in water and thermal management. Te bipolar plate mate-
rials should have high electrical and thermal conductivity,
good corrosion resistance, sufcient compressive strength,
Hindawi Publishing Corporation
Journal of Chemistry
Volume 2014, Article ID 371616, 7 pages
http://dx.doi.org/10.1155/2014/371616