The present disclosure relates in part to a flow field structure comprising a hydrophilic part and a hydrophobic part communicably attached to each other via a connecting interface. The present disclosure further relates to electrochemical cells comprising the aforementioned flow fields

Pien, Shyhing M.

Warshay, Marvin

NASA Technical Reports Server

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(12) United States Patent 
Pien et al. 
(54) INTEGRATED FLOW FIELD (IFF) 
STRUCTURE 
(75) Inventors: Shyhing M. Pien, Acton, MA (US); 
Marvin Warshay, Shaker Heights, OH 
(US) 
(73) Assignee: ElectroChem, Inc., Woburn, MA (US) 
(*) Notice: 	 Subject to any disclaimer, the term of this 
patent is extended or adjusted under 35 
U.S.C. 154(b) by 967 days. 
(21) Appl. No.: 12/262,975 
(22) Filed: 	 Oct. 31, 2008 
(65) 	 Prior Publication Data 
US 2009/0136789 Al 	 May 28, 2009 
Related U.S. Application Data 
(60) Provisional application No. 60/984,097, filed on Oct. 
31, 2007. 
(51) Int. Cl. 
H01M8104 	 (2006.01) 
(52) U.S. Cl . ......................... 429/429; 429/428; 429/400 
(58) Field of Classification Search ................... 429/429 
See application file for complete search history. 
	
(1o) Patent No.: 	 US 8,313,870 B2 
(45) Date of Patent: 	 Nov. 20, 2012 
(56) References Cited 
U.S. PATENT DOCUMENTS 
	
5,322,744 A 	 6/1994 Koseki et al. 
	
5,641,586 A 	 6/1997 Wilson 
	
5,840,414 A 	 11/1998 Bett et al. 
	
6,197,442 131 	 3/2001 Gorman 
2005/0208366 Al 	 9/2005 Rohwer et al. 
2006/0199061 Al* 	 9/2006 Fiebig et al . .................... 429/32 
2006/0286429 Al 	 12/2006 Shiepe et al. 
FOREIGN PATENT DOCUMENTS 
KR 	 10-2007-0023219 	 2/2007 
WO 	 WO-03/058743 	 7/2003 
OTHER PUBLICATIONS 
International Search Report dated Jul. 29, 2009 from PCT/US2008/ 
082099. 
* cited by examiner 
Primary Examiner Raymond Alejandro 
Assistant Examiner Gary Harris 
(74) Attorney, Agent, or Firm Foley Hoag LLP 
(57) ABSTRACT 
The present disclosure relates in part to a flow field structure 
comprising a hydrophilic part and a hydrophobic part com-
municably attached to each other via a connecting interface. 
The present disclosure further relates to electrochemical cells 
comprising the aforementioned flow fields. 
15 Claims, 8 Drawing Sheets 
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connecting interface 
wet 
part, 
U.S. Patent 	 Nov. 20, 2012 	 Sheet 1 of 8 	 US 8,313,870 B2 
Figure 1 
Figure 2 
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U.S. Patent 	 Nov. 20 , 2012 	 Sheet 2 of 8 	 US 8 ,313,870 B2 
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U.S. Patent 	 Nov. 20,2012 	 Sheet 3 of 8 
	
US 8,313,870 B2 
Figure 6 
Electrodes — for electrochemical cells 
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Figure 7 
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electrode 
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5 
6 
U.S. Patent 	 Nov. 20, 2012 	 Sheet 4 of 8 	 US 8,313,870 B2 
Figure 8 
U.S. Patent 	 Nov. 20, 2012 	 Sheet 5 of 8 	 US 8,313,870 B2 
Figure 9 
Part 2 
NOWEE 
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Part 3 
U.S. Patent 	 Nov. 20, 2012 	 Sheet 6 of 8 	 US 8 ,313,870 B2 
Figure 10 
Porous channels designed to direct water and vapor. 
(with two possible arrangements) 
2-A arrangement – same properties 
Hydr(sphilic XWOM 
2-13 arrangement – alternate properties 
hydrophobic 
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Porous channels designed to direct reactant gas and water vapor. 
(with two possible arrangements) 
3-A arrangement – same properties 
hydrophobi 
3-13 arrangement – alternate properties 
hydrophobic — 
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hydrophobic — I IMMOM 
Figure 11 
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U.S. Patent 	 Nov. 20, 2012 	 Sheet 7 of 8 	 US 8,313,870 B2 
U.S. Patent 	 Nov. 20, 2012 	 Sheet 8 of 8 	 US 8,313,870 B2 
Figure 12 
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US 8,313,870 B2 
1 
INTEGRATED FLOW FIELD (IFF) 
STRUCTURE 
RELATED APPLICATIONS 
This application claims the benefit of priority to U.S. Pro-
visional Patent Application No. 60/984,097, filed on Oct. 31, 
2007, which is herein incorporated by reference in its entirety. 
GOVERNMENT SUPPORT 
This invention was made with Government support under 
NASA SBIR Contract Nos. NNJ06JD71C and NNJ07AIOC 
awarded by the National Aeronautics and Space Administra-
tion (NASA). The Government may have certain rights in the 
subject invention. 
BACKGROUND 
A flow field is a configuration that is specifically designed 
to distribute gas, liquid, vapor, or a combination thereof. A 
flow field is usually confined inside a compartment, and the 
compartment defines the boundary of the flow field and pro-
vides one or more access points to the flow field for the 
introduction of reactants and removal of byproducts. Flow 
fields are often used in connection with electrochemical cells. 
Electrochemical cells operate by reacting with the reac-
tants and producing electrons generating current and poten-
tial. A typical electrochemical cell consists of electrodes 
separated by a layer of electrolyte. The electrodes can be 
defined as anode and cathode electrodes or working and 
counter electrodes. A separate reference electrode can also 
introduce to the electrochemical cell. Gas that comes in con-
tact with the electrodes first passes through an opening flow 
field (or channels) then diffuses through a barrier of the elec-
trode and eventually reacts at the surface of the electrode 
involving either an oxidation or reduction reaction mecha-
nism. These reactions are catalyzed by the electrode materials 
specifically developed for the reactants of interest. 
For example, an electrochemical fuel cell specific to hydro-
gen and oxygen has an anode and cathode electrodes. The 
anode electrode produces electrons and protons for the oxi-
dation of hydrogen at the anode. During a simultaneous 
reduction of the cathode, the electrons generated at the anode 
release and travel via an external circuit to the cathode where 
oxygen molecules consume the electrons (reduced) and form 
water by further combining the protons which travel via the 
electrolyte layer. The electrochemical fuel cell has been 
developed to convert fuel (hydrogen, alcohols such as metha-
nol or ethanol, hydrocarbon, carbon oxides) and oxidant 
(such as oxygen, air) to generate electric energy; in other 
words, they convert the free energy of reaction of a fuel with 
an oxidant without degrading it completely to thermal energy. 
This conversion is achieved through the electrochemical oxi-
dation of the fuel at the anode, with the consequent release of 
electrons and protons, while the oxidant is reduced at the 
cathode. The migration of the protons from the anode to the 
cathode compartment of the cell takes place through a suit-
able electrolyte. 
When a solid polymer electrolyte is applied in electro-
chemical cells, such as polymer electrolyte membrane fuel 
cells (PEM fuel cells), the integration of the anode electrode, 
cathode electrode and electrolyte layer forms a membrane 
electrode assembly (MEA). Oxidation and reduction reaction 
occurred at the electrodes. The formed protons permeate 
2 
through the polymer electrolyte membrane. The formed elec-
trons travel along an external load circuit to create the current 
output of the fuel cell. 
In a reverse process, electrolysis, which is commonly car- 
5 ried out in an electrolyzer, the liquid water (e.g., the product 
of the fuel cell) is converted back to the reactant gases (e.g., 
hydrogen and oxygen useable by the fuel cell). When the fuel 
cell and electrolyzer are operated in concert as two separate 
electrochemical cells or as a single electrochemical energy 
io storage unit it is commonly called a regenerative fuel cell 
("RFC"). Furthermore, a single electrochemical energy stor-
age unit is commonly called a Unitized RFC to indicate that 
both the fuel cell process and the electrolysis process are 
carried out during different cycles within a single electro- 
15 chemical cell. 
Fuel cells utilizing a polymer electrolyte membrane (PEM) 
are typically configured in cell stacks having separator plates 
between adjacent membrane electrolyte assemblies (MEAs). 
On each side of the polymer electrolyte membrane, there is an 
20 electrode. One side is the anode electrode and another side is 
the cathode electrode. The separator plates and polymer elec-
trolyte membranes keep the reactants separated between the 
anode and cathode of the electrochemical fuel cells. Flow 
fields (that are usually part of the separator plates) direct the 
25 reactants to the electrodes. The flow fields also direct the 
products out of the cells. 
Fuel cells are considered to be an excellent alternative to 
the traditional systems of electric generation, mostly due to 
the extremely favorable environmental impact (absence of 
3o noxious emissions and noise, release of water as by-product). 
They can be used both in the field of stationary power gen-
eration of various size (electric plants, continuity or emer-
gency power generators, etc.) as well as in the field of mobile 
applications (electric automotive applications, generation of 
35 automotive energy or auxiliary energy for space, submarine 
and naval applications). 
Electrochemical cells, such as fuel cells and electrolyzers, 
have inherent problems associated with the changes of phase 
that occur in the cell when, upon reaction, gaseous reactants 
40 are converted to water or water vapor (in fuel cells) or the 
reactant water to oxygen and hydrogen gases (in electrolyz-
ers). After some of the reactants have been converted to prod-
uct, they must be directed away from the electrode catalytic 
reaction sites to avoid blocking access to these sites to the 
45 unreacted reactants. The undesirable condition called "flood-
ing" can occur when product water blocks reactant access to 
the electrode catalytic reaction sites. The undesirable condi-
tion called "dryout" can occurs in the electrolyte layer when 
large amounts of dry reactant gas are introduced in the fuel 
50 cell. Thus, water management in fuel cells is complicated by 
two seemingly conflicting requirements associated with two 
vital elements of the system: the proton exchange membrane 
must be kept sufficiently hydrated in order to avoid dry out 
effectively conduct protons. At the same time, the catalytic 
55 sites on which the two half-reactions take place must be 
continuously supplied with gaseous reactants and kept rela-
tively dry in order to efficiently proceed with the catalytic 
reaction. 
Flow fields are used in electrochemical cells to attempt to 
6o resolve some of these issues, but with certain drawbacks. 
Flow fields are typically fabricated in separator plates by 
machining flow fields into a solid sheet of material or by a 
molding process. The flow fields are made up of a series of 
channels or grooves that allow passage of gases and liquids. 
65 In order to conduct electrons through the electrochemical 
cells, these separator plates are typically made of graphitic 
carbon or a variety of metals. The central portion on the plate 
US 8,313,870 B2 
3 
has a flow field machined into its surface. The flow field 
directs fluid flow across the surface of the electrode in many 
patterns. Around the perimeter of the flow field, the plate 
provides various manifolds for communicating fluids through 
the stack. In addition to usually providing a fluid flow field, a 
separator plate used in electrochemical cells collects and 
conducts electrons through contact between electrodes and 
the ridges, or lands, in the flow field. 
In electrolyzer operation, a poor distribution of water reac-
tant to the electrode electrocatalyst site occurs when gaseous 
product is trapped inside the flow channels. Current flow field 
designs comprising machined or molded channels in a hard 
plate, no matter how sophisticated in design, are inherently 
inefficient in directing the products away from the electrode 
catalytic reaction sites. Another inherent problem associated 
with PEM fuel cells is the formation of condensed water 
droplets in the gas distribution channels, which block gas flow 
in the channels and can cause severe operational problems, 
even cell failure, in conventional designs. 
In a chemical sensor, proper flow of liquids and gas are 
needed for accurate detection of the presence of certain 
chemicals. 
Thus, there is a need for a flow field structure, which 
provides more ideal conditions inside of electrochemical cell. 
SUMMARY 
Provided herein is an Integrated Flow Field (IFF) structure, 
comprising a hydrophobic part and a hydrophilic part in com-
munication with each other via a connecting interface. The 
hydrophobic part and hydrophilic part comprise porous mate-
rial and have a porosity of 30% to 100%. Preferably, the 
communication between the hydrophobic and hydrophilic 
parts is such that a liquid, vapor, a gas, or a mixture thereof, 
can flow between the hydrophilic and hydrophobic parts. In 
some embodiments, the flow field structure comprises a plu-
rality of hydrophobic parts and a plurality of hydrophilic parts 
in communication with each other. In other embodiments the 
hydrophobic parts and hydrophilic parts are hydrophobic 
channels and hydrophilic channels, respectively. 
In some embodiments, the hydrophobic and hydrophilic 
channels comprise a porous material, wherein the porous 
material has a porosity of 30 to 100%. 
In some embodiments, the hydrophobic channels and 
hydrophilic channels are provided in an alternating configu-
ration. In other embodiments, the hydrophobic channels and 
hydrophilic channels are provided in a random configuration. 
In still other embodiments, the hydrophobic channels and 
hydrophilic channels are provided in an interlocking configu-
ration. 
In certain embodiments, the number of hydrophobic chan-
nels is equal to the number of hydrophilic channels. In other 
embodiments, the number of hydrophobic channels is greater 
than the number of hydrophilic channels. In other embodi-
ments, the number of hydrophobic channels is less than the 
number of hydrophilic channels. In other embodiments, the 
flow field structure comprises 2 to 20 hydrophilic channels 
and 2 to 20 hydrophobic channels. 
In some embodiments, each channel has a span to width 
ratio ranging from about 1/2 to about 1/10. 
In some embodiments, the hydrophobic part and hydro-
philic part comprise graphitic carbon fiber mat, fiber cloth, 
graphitic carbon paper, sintered metal, metal forms, mesh, 
screen, reticulated vitreous carbon, or a combination thereof. 
In other embodiments, the hydrophobic part and hydrophilic 
part comprise graphitic carbon paper, such as Toray® gra-
phitic carbon. In some embodiments, the hydrophobic part 
4 
comprises between about 5% to about 60% Teflon. In other 
embodiments, the hydrophilic part comprises between about 
1 and 60% Nation. 
In some embodiments, the flow field structure further com- 
5 prises a manifold in communication with the hydrophobic 
part or the hydrophilic part. In other embodiments, the flow 
field comprises a manifold in communication with the hydro-
phobic part and a manifold in communication with the hydro- 
10 
philic part. 
In some embodiments, the flow field structure is provided 
within a separator plate. In other embodiments, the flow field 
structure, which may or may not be provided in a separator 
plate, is provided in an electrochemical cell. The electro- 
15 chemical cell may be a fuel cell, an electrolyzer, a regenera-
tive fuel cell or a chemical sensor. 
In other embodiments, the flow field structure is comprised 
within a separator plate for a fuel cell stack. 
Another aspect of the invention relates to a subassembly 
20 for an electrochemical cell, comprising: 
(a) a membrane electrode assembly; 
(b) an electrode gas distribution layer; 
(c) a flow field structure comprising a hydrophobic part and 
a hydrophilic part in communication with each other via a 
25 porous interface; 
(d) a separator plate or frame; 
(e) an input manifold; 
(f) an output manifold; 
(g) a sublayer for humidifying input gas; and 
30 	 (h) an impermeable electronic conductive framework. 
In other embodiments of the subassembly, the flow field 
structure is provided in the separator plate or frame. In some 
embodiments, the sublayer for humidifying gas comprises a 
porous material. 
35 	 Another aspect of the invention relates to a fuel cell stack, 
comprising at least one of the aforementioned subassemblies. 
Another aspect of the invention relates to a method for 
controlling fluid flow in an electrochemical cell comprising: 
a) providing an electrochemical cell comprising a flow 
40 field structure comprising a hydrophobic part and a hydro-
philic part in communication with each other via a porous 
interface; an input manifold in communication with the 
hydrophobic part or the hydrophilic part; and an output mani-
fold in communication with the hydrophobic or the hydro- 
45 philic part; 
b) introducing a liquid, vapor, gas, or mixture thereof into 
the electrochemical cell via the input manifold; and 
c) removing a the liquid, gas, vapor, or mixture thereof 
from the electrochemical cell via the output manifold. 
50 In some embodiments, the liquid, gas, vapor, or mixture 
thereof introduced into the cell comprises H z . In other 
embodiments, the liquid, gas, vapor, or mixture thereof 
removed from the electrochemical cell comprises water. In 
another embodiment the liquid, gas, vapor, or mixture thereof 
55 removed from the cell comprises H z . 
Further objectives and advantages of the present invention 
will become apparent as the description proceeds. To gain a 
full appreciation of the scope of the present invention, it will 
be further recognized that various aspects of the present 
60 invention can be combined to make desirable embodiments of 
the invention. 
BRIEF DESCRIPTION OF THE DRAWINGS 
65 	 FIG.1 depicts an embodiment of a flow field, comprising a 
hydrophobic part and a hydrophilic part, which is in commu-
nication via a connecting interface. 


Integrated flow field (IFF) structure

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