Highly Efficient Polymer
Electrolyte Fuel Cell (PEFC)
Contributing to the EnvironmentPEFC
TADASHI GENGO*1

YOSHINORI KOBAYASHI*1

YASUSHI MORI*1

HIROSHI HIRAYAMA*2TOSHIHIRO TANI*2

SETSUO OHMOTO*3

Photo provided by the Japan Agency for
Marine-Earth Science and Technology (JAMSTEC)SHIGERU TSURUMAKI*4

Based on the accumulation of the basic technology for catalysts, combustion, heat transfer, etc., Mitsubishi Heavy Industries, Ltd.
(MHI) has been developing the technology for high performance membrane electrode assemblies (MEA) for polymer electrolyte fuelcells (PEFC) and has also been developing the major components such as the reformer and fuel cell stack. At the same time MHI isworking on the development of a PEFC system for stationary distributed power sources and power sources in special environments byusing the company’s system design and control technology. An outline of the development status of MHI’s PEFC is introduced below.

1. Introduction
Fuel cells are next-generation low emissions and highefﬁciency power source and their use is expected to become
widespread in the near future. In particular, the applicationof of PEFC to distributed power supplies, and movablebodies is accelerating through making the best use of its
low temperature operation at 80 to 120°C. This reportintroduces the basic PEFC technology implemented byMHI, the kerosene-fueled stationary power supply system
now in development, the hydrogen-fueled system for special
applications, and the full closed type ultra-high efficiency
power generation system.

2. Development of basic technology
MHI has identified that hydroxyl radicals are the main

Fuel electrodecatalyst layer

H2H2HO-H+H+HOH2O
H2O2

Radical capture layer

Polymer
membrane

Air electrodecatalyst layer
O2
H2O21.00

H2 O

H2O2

OCV voltage drop not observed.

Average voltage (V)Radical capture layer

factor which deteriorate polymer membranes, due to theretention of an open circuit voltage (OCV) associated withthe startup and shutdown of the system as well as to thehydrogen peroxide by-product inside the electrode catalyst
layer under dry conditions. Based on this ﬁnding, MHI has
developed an original long-life MEA which forms a radicalcapture layer to capture or stabilize the hydrogen peroxide
radicals before they reach the polymer membrane (Fig. 1).
MHI is now implementing a short stack test by using thisMEA and is in process of conﬁrming it has sufﬁcient stability
and a voltage drop rate of 3 mV/1,000 hrs has so far been
conﬁrmed (Fig. 2).
Next, to investigate the polymer membrane deterioration
inhibition effect of the radical capture layer, we measured theamount of fluorine ions contained in the discharged water
during the generation of electricity. (The elution of ﬂuorine

H+H2O2

HOHO-H2O

0.80
0.60

Cumulative electric
generation hours
3,500 hrs0.40
0.20
0.00

01000

2000

3000

4000

Cumulative electric generation hours (hrs)Fig. 1 Radical capture layer
Deterioration of the polymer membrane is prevented by the radicalcapture layer which is formed in the boundary between the polymer
membrane and the catalyst layer.

Fig. 2 Stability of radical capturing layer MEA
Voltage stability in the early stage of power generation wasconﬁrmed.

*1 Power Systems Headquarters*2 Kobe Shipyard & Machinery Works*3 Hiroshima Research & Development Center, Technical Headquarters3737*4 Nagasaki Research & Development Center, Technical HeadquartersMitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)

ions composing the polymer if the polymer membrane has
been decomposed due to deterioration has been conﬁrmed.)
The amount of elution of fluorine ions from MEA with theradical capture layer is lower than that from MEA without theradical capture layer and thus a high deterioration inhibition
effect is indicated (Fig. 3).

(Hiroshima Diamond Hotel) in the city of Hiroshima, where
the total efﬁciency of 83% was achieved and the cumulative
power generation of 10,000 hours was attained by June 2007
(Fig. 4).
Fur t her more, i n December 2 0 0 6 M H I i nst a lled a n
improved system of the same type in a public warm water
swimming pool and achieved the target generating efﬁciencyof over 36% (LHV: lower heating value) and is still performing
continuous operation tests.
In addition, MHI is also developing a pure hydrogenf ueled 10 kW class PEFC system for power supplies todeployment in vehicles. The pure hydrogen type fuel cellstarts quickly, achieves clean power generation and there isless noise and vibration. Because of these characteristics,
it is thought that the mobile pure hydrogen-fueled PEFC
systems will be very convenience for wide-spread use such as
an emergency power supply in disasters, a power supply forconstruction and illumination in ill-ventilated places, and as
a power supply for outdoor events (Fig. 5).

3. Actual application to stationary use

Cathode drain in-water fluorine elution* (-)

MHI is developing a kerosene-fueled 10 kW class PEFC
system in cooperation with Nippon Oil Corporation (NOC)
for the “Stationary Fuel Cell Demonstration Study in Fiscal
Year 2003,” a government-sponsored project of the New
Energy Foundation (NEF). A field demonstration of thesystem was carried out at a convenience store from February
2004 for one year. In addition, in June 2005, MHI installed
the same t y pe of PEFC system in a commercial hotel

1.0: Without radical capture layer: Radical capture layer MEA

0.80.6
0.4
0.2
0.0

0100

200

300

400

500

600

700

Cumulative power generation hours (hrs)* Relative value of MEA without a radical capture layer
when the integrated value of fluorine dissolution isassumed to be 1 (one).

Fig. 3 Deterioration inhibition effect of radical capture layer
MEA
Fluorine elution restriction effect by the radical capture layer andpolymer membrane deterioration inhibition effect were conﬁrmed.
Fig. 5 Pure hydrogen-fueled 10 kW class
PEFC system
This system is useful in applications which
requires features such as quick start-up,
clean power generation, and less noise andvibration.

4. Actual use in special applications
The PEFC is compact and highly ef ficient, has good
operability and a high generating efficiency of nearly 60%
through the use of pure hydrogen and oxygen fuel, andthe advantage that water is the only discharge from powergeneration. Making best use of its characteristics, its use
as a power source in closed space is also promising. One
example of a closed space is underwater vehicles, for which
specific technological challenges that are not found in thestationary system and mobile land vehicles are additionallyFig. 4 Kerosene-fueled 10 kW class PEFC system
MHI performed a demonstration test at a hotel which requires
power generation 24 hours a day and a huge hot water supply. As aresult, the target performance was achieved.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)38

Fig. 6 Autonomous underwater vehicle Urashima
Urashima achieved 317 km continuous navigation which is a world
record for an autonomous underwater vehicle. (Photograph suppliedby JAMSTEC.)

Table 1 Main speciﬁcations of PEFC on Urashima
Output

4 kW（2 kW × 2）

Operation temperature

60°C

Power generation efficiency

54%

Fuel

Pure hydrogen/pure oxygenFig. 7 PEFC installed on Urashima
The 4 kW class fully closed loop typewas adopted for use in the operational
environment of a closed underwater space.

required, including the f uel supply system, discharge
treatment, retention of operating temperature, and highair tightness. MHI has overcome these technologicalchallenges through the adoption of a metallic separator andhas manufactured a 4 kW class fully closed type PEFC as
the power source for Urashima, an autonomous underwater
vehicle (AUV) of the Japan Agency for Marine-Earth Scienceand Technology (JAMSTEC). Using this equipment,
Urashima attained 56 hours continuous operation in a runningtest carried out in Suruga Bay in February 2005 and achieved
continuous navigation for 317 km which is a world record foran autonomous underwater vehicle (Figs. 6 & 7, Table 1).
T his f ully closed t ype PEFC is based on promisingtechnology which is useable not only for underwater vehicles
but also for fully regenerative power generation systems
such as those on satellite stations, and lunar bases andwhose future development is highly anticipated.

Tadashi Gengo

Yoshinori Kobayashi

Yasushi Mori

5. Conclusion
The company intends to promote the PEFC fuel cell bymaking best use of its highly efficient, low temperaturepower generation, while considering its use in emergencies
and on mobile objects, etc.
This technology was fostered as a sponsored project of
the New Energy and Industrial Technology Development
Organization (NEDO) and related collaborative research.
Finally, we would like to express our sincere gratitude to thesponsor and our research partners.

Hiroshi Hirayama

Toshihiro Tani

Setsuo Ohmoto

Shigeru Tsurumaki

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)39