Journal of Energy Chemistry 36 (2019) 129–140

Contents lists available at ScienceDirect

Journal of Energy Chemistry

journal homepage: www.elsevier.com/locate/jechem

Review

Recent progresses in H 2

-PEMFC at DICP

Feng Xie

a , b , Zhigang Shao

a , ∗, Ming Hou

a , Hongmei Yu

a , Wei Song

a , Shucheng Sun

a , Li Zhou

a , Baolian Yi a

a Division of Fuel Cell and Battery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China b University of Chinese Academy of Sciences, Beijing 10 0 039, China

Dedicated to the 70th anniversary of Dalian Institute of Chemical Physics, CAS, China.

a r t i c l e i n f o

Article history:

Received 17 April 2019

Revised 15 July 2019

Accepted 15 July 2019

Available online 24 July 2019

Keywords:

PEMFC

Catalysts

MEAs

Metal bipolar plates

Fuel cell stacks

Low temperature startup

Durability

Control strategy

a b s t r a c t

Proton exchange membrane fuel cell (PEMFC) as a power supply device has attracted wide attention

in China and abroad for its advantages of high energy density, energy conversion efficiency and zero

pollution. With the vigorous support of China’s national policy, research institutes and enterprises have

carried out extensive and pragmatic work on the basic materials, key components, stacks, auxiliary sys-

tems of PEMFCs, as well as the hydrogen station construction in order to realize the wide application of

hydrogen energy. PEMFC System and Engineering Research Center of DICP is one of the earliest players

in the H 2 -PEMFCs field. Advances have been achieved in the fields of low-platinum contained catalysts,

PEMs, high-efficiency MEAs, low-cost metal bipolar plates, low-temperature and impurity air environment

adaptability, stacks and systems. This paper introduces recent progresses of H 2 -PEMFCs at DICP in key

materials, components, stacks, systems and the applications. The engineering status of proton exchange

membrane water electrolysis (PEMWE) and the alkaline anion exchange membrane fuel cells (AEMFCs)

are also summarized.

© 2019 Published by Elsevier B.V. and Science Press on behalf of Science Press and Dalian Institute of

Chemical Physics, Chinese Academy of Sciences

Feng Xie , getting his first full time job in 2012, and now

is a Ph. D. candidate of chemical engineering tutored by

professor Baolian Yi and Zhigang Shao. His research in- terests are poisoning effects of fuel cell catalysts, synthe-

sis of alkaline anion exchange membrane and the water management of AEMFC and PEMFC. He also gains some

experience on producing AEMs and bipolar plates at scale.

Dr. Zhigang Shao , professor, Ph. D. adviser, choice of Ten

Thousand Talent Program of China , the head of division of fuel cell and battery, also the leader of fuel cell system

and engineering research center of DICP, CAS, has long been devoted to fuel cell system engineering and system

integration technology research. He has published more

than 190 academic papers and applied for more than 200 patents, in which more than 50 patents are granted. The

directions of the research center also include catalysts, membranes, MEAs, bipolar plates and stacks of PEMFC

and PEMWE, and the process engineering and technolo- gies of PEMFC.

∗ Corresponding author.

E-mail address: zhgshao@dicp.ac.cn (Z. Shao).

Dr. Ming Hou , professor, Ph. D. adviser. Her research in- terests include PEMFC electrode materials, bipolar plates,

stacks and relevant components, as well as the fun- damental researches on PEMFC degradation mechanism,

durability enhancement and operating strategies etc. She has published more than 100 academic papers, and par-

ticipated in the formulation of more than 15 fuel cell

standards of China. She won the first prize of scien- tific and technological progress in Liaoning Province and

the first-class award of Dalian scientific and technological progress.

Dr. Hongmei Yu , Professor, Ph. D. adviser, leader of high efficiency water electrolysis team (B), deputy general

secretary of National Technical Committee 342 on Fuel Cell and Flow Battery of Standardization Administration of

China , fuel cell standard expert in IEC TC105. Her research

interests include membrance electrode assembly (MEA), interface phenomena in fuel cells and water electrolysis,

subzero startup of PEMFCs, photoelectrochemical cell and alkaline exchange membrane (AEM) fuel cell. She

authored more than 90 publications in peer-reviewed journals and more than 120 patents.

https://doi.org/10.1016/j.jechem.2019.07.012

2095-4956/© 2019 Published by Elsevier B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences

130 F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140

Dr. Wei Song , associate professor, master advisors, leader

of PEMFC key material team (B). Her research interests fo- cus on MEAs of PEMFC, including the structures, interface

phenomena, performance and durability, especially under

low Pt loading conditions. She also gains plenty of experi- ence on setting up patch production line of MEAs. By now

she has published more than 10 academic papers and ap- plied for more than 20 patents.

Dr. Shucheng Sun , professor, master advisors, leader of

PEMFC key technology team (B). His research interests in- clude water management of PEMFC and PEMWE stacks

and systems, mainly on the durability and high pressure of produced gases, as well as enlarging the gas production

scale. He has gained the first-class award of Dalian Scien- tific and Technological Progress. Until now, he has pub-

lished more than 17 academic papers, and applied for 35

patents.

Dr. Li Zhou , professor, master advisors. His research in-

terests include the stack and systems of MCFC, SOFC, PEMFC and RFC, especially the applications of the fuel

cell systems. He is the choice of Key Technology Talents Program of Chinese Academy of Sciences, and won the

first-class award of Dalian Technological Invention. He has

published 10 academic papers and applied for 31 patents until now.

Professor Baolian Yi , Academician of Chinese Academy of

Engineering, a chief scientist in China 863 high-tech pro- gram. His research field covers alkaline fuel cell, molten

carbonate fuel cell, PEMFC, regenerative fuel cell, direct methanol fuel cell and solid oxide fuel cell and so on.

He founded the R& D Centre on Fuel Cells of DICP in

1968. He led to set up the China Fuel Cell Test Centre. He also led to establish the National Engineering Centre

of Fuel Cell & Hydrogen Technology. He has trained more than 100 masters and doctors, who are now professors

and senior engineers, and most of them play important roles in China’s fuel cell academic world and industrial

world.

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1. Introduction

Proton exchange membrane fuel cell (PEMFC) is an energy con-

version device that directly converts chemical energy in fuel and

oxidant into electrical energy by electrochemical reaction [1] . A

typical PEMFC module is given in Fig. 1 (a), including fuel cell

stacks, air supply system, H 2 supply system, electronic control unit

(ECU), voltage inspector and the thermal treatment system. The ex-

ploded view of the PEMFC stack is given in Fig. 1 (b), which in-

cludes the end plates, current collectors, bipolar plates, gaskets,

and MEAs that are constitute of gas diffusion layers (GDL), cata-

lyst layers (CL) and the proton exchange membrane (PEM). With

the advantages of high energy efficiency, no pollution and zero

carbon emission, PEMFC is considered to be of broad application

prospects in portable power supply, automobile power supply and

fixed power station and military applications. With the sustained

support of national programs and the investment of enterprises,

PEMFC is now in an explosive period of large-scale commercial-

ization, especially in the vehicle power field. Improving the power

density of fuel cells is strongly demanded [2] , which requires to

evelop catalysts with higher activity, super thin composite mem-

rane, metal bipolar plates and the scale up producing technology.

he cost and life are also the obstacles. At present, the platinum

oad of PEMFC is relatively high [3] , and the life of key compo-

ents such as membrane electrode assemblies (MEAs) and bipolar

lates (BPs) cannot meet the needs of commercial applications, for

xample 20,0 0 0 h for cars or 10 0,0 0 0 h for stationary power sta-

ion. At the same time, the mastery of environmental adaptation

echnology and system integration technology still need to be pro-

oted to address the problems on low temperature start-up, air

urification and performance deterioration. It is still necessary to

urther improve the performance, reduce the cost and prolong the

ife of PEMFCs.

As the heart of a fuel cell system, the stack is expected to be

equentially promoted in power density, mainly by increasing the

orking current density with limited potential loss [4] . The perfor-

ance of MEAs and the resistance of bipolar plates are the key

oints. Pt-based alloy catalysts, ordered electrodes and ultrathin

omposite reinforced PEMs are beneficial for the MEAs, while the

urface modified stainless steel plate plays a great role in reducing

he contact resistance. The design of the flow field and the anode

ater management also significantly affect the power density, es-

ecially when the current density is higher than 500 mA cm

−2 . In

ddition, the mass-produce technologies of MEAs and bipolar plate

nd the batch production process design are the key preconditions

or PEMFCs’ commercialization.

In order to reduce the cost of fuel cell to realize the commercial

pplication of PEMFCs, improvements have been made in key ma-

erials, components, stacks and systems. Alloy catalysts with low

t loading and high performance are extensively studied [5] . Stain-

ess steel-based metal bipolar plates with costless coatings are also

eveloped. Advancing the electrode preparation technology to im-

rove the utilization ratio of the Pt catalysts in MEAs is important.

ots of researches focus on raising the power density of the PEMFC

tack and reducing the cost of the auxiliary system by simplifying

he system. In addition, alkaline anion membrane fuel cells are also

onsidered to be of great potential to reduce the cost [6,7] . In or-

er to reduce the life cycle costs, prolonging the life of PEMFCs is

lso claimed to be effective ways.

Much work has been done to improve the durability of PEM-

Cs. The stability of the catalyst is improved from both support

nd metal components. Radical quenching agent is used to im-

rove the anti-oxidant of the PEMs [8] . The corrosion resistance

f metal bipolar plates is also enhanced. The structure of MEAs

s designed and optimized to be stable. By finely adjusting the

perating strategy, the life of the stacks is promoted. Lots of re-

earches also aim at keeping the performance of the stacks and

he quick start-up ability in low temperature environment. Be-

ides, tolerance of impurity air such as NO x and SO x is studied

9,10] . At the system level, employing hydrogen circulating pump

o promote the management of anode water can greatly improve

he life of PEMFCs. The life of PEMFC can also be greatly im-

roved by using the hybrid power of fuel cell and Li-ion battery in

utomobiles.

Since 1994, the H 2 -PEMFCs have been studied in Dalian Insti-

ute of Chemical Physics (DICP). PEMFC System and Engineering

esearch Center of DICP is one of the earliest players in the H 2 -

EMFCs. A series of advances have been achieved in the fields

f low-platinum contained catalysts, PEMs, high-efficiency MEAs,

ow-cost metal bipolar plates, low-temperature and impurity air

nvironment adaptability, stacks and systems. This paper intro-

uces recent progresses of H 2 -PEMFCs at DICP in key materials,

omponents, stacks, systems and the applications, and also the en-

ineering status of proton exchange membrane water electrolysis

PEMWE) and the alkaline anion exchange membrane fuel cells

AEMFCs).

F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140 131

Fig. 1. Composition of PEMFC. (a) PEMFC module and (b) PEMFC stack.

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. Progresses in H 2 -PEMFC at DICP

.1. Low-platinum contained catalysts

.1.1. 3D graphene modified carbon black support

Catalyst support can improve the dispersion of Pt nanoparticles

NPs), leading to a higher utilization ratio of Pt. Also the strong

nteractions between the support and Pt nanoparticles can also

mprove the activity and stability of catalysts. A qualified cata-

yst support for PEMFCs should be of large specific surface area,

ood conductivity and corrosion resistance under the operating

onditions [11,12] . A variety of supports including carbon free

aterial such as SnO 2 and TiN, and carbon based supports such as

ctive carbon, carbon nanotubes and graphene are widely studies

13] . Graphene draws lots of attentions owing to its large specific

urface area, remarkable electrical conductivity and high resistance

o electrochemical corrosion in acid media [14,15] . However, the

tability of graphene needs to be further improved because of

ts tendency to restack due to π- π stacking and Van der Waals

nteractions, as well as the decrease of electroconductivity re-

ulting from the defects introduced by the reduction of graphene

xide. To avoid these shortcomings, three-dimensional (3D) hybrid

tructures built of graphene and other nanomaterial with good

onductivity such as WC, g-C 3 N 4 nanosheets and carbon fiber

ave been developed. Unfortunately, their applications as catalyst

upports for the ORR under PEMFC operating conditions have been

eldom addressed, and the complexity of preparation, high energy

onsumption and high cost in the preparation process also limit

heir commercial applications.

A facile and cost-effective approach is developed at DICP to

abricate a novel 3D hierarchical architecture constructed from re-

uced graphene oxide and poly(diallyldimethylammoniumchloride)

unctionalized carbon black (rGO-FCB), on which Pt NPs is fur-

her loaded ( Fig. 2 (a)) [16] . The electrode prepared with this ar-

hitecture demonstrates superior performance in single cell test,

ith a peak power density of 1.344 W cm

−2 and a maximum

ass specific power density of 7.5 W mg Pt −1 , which are 1.25

old greater than those of the conventional Pt/C electrode. The

atalysts with this support also possess superior cycling stabil-

ty, with a 5% diminution of the power density, which is much

ower than that of the conventional Pt/C electrode (21%) in the

ame accelerated degradation test (ADT, Fig. 2 (b)). The intercon-

ected 3D porous structure effectively prevents the restacking of

he graphene sheets. The strong interaction between Pt NPs and

he rGO–FCB composite provides a stabilizing effect against Pt de-

achment/dissolution. High graphitic crystallinity provides electron

onduction highways and is more resistant to oxidation/corrosion

nder harsh electrochemical conditions. As a result, the ORR activ-

ty and durability for PEMFC are greatly enhanced.

.1.2. Pt 3 Pd alloy catalyst

Considering the slow ORR kinetics in the cathode, a number of

recious metals such as Pt are employed as the catalysts, resulting

n the high cost of the PEMFCs. Reducing the load of Pt catalyst

ill directly reduce the cost. One practicable route is to develop

ow-platinum or platinum-free catalysts, which are often of low ac-

ivity and poor stability [17] . Alloy catalysts composed of platinum

nd cheap transition metals are proved to have high activity and

tability with low platinum loading. The electronic and geometric

tructures of Pt-based alloy nanocatalysts are tailored by different

ompositions, structures and morphologies to weaken the adsorp-

ion strength of OH ad on the surface of Pt atoms and enhance the

RR activity [18,19] .

PtPd alloy catalysts with high durability and ORR activity are

ynthesized at DICP on a large scaled and employed as the cathode

atalysts for PEMFC stacks ( Fig. 3 (a)) [20,21] . The Pt 3 Pd/S770 cat-

lyst is prepared in a continuous stirred tank teactor (CSTR) with

thylene glycol as the reducing agent. The initial performance of

he Pt3Pd/S770 catalyst is the same to the commercial Pt/C cata-

ysts. However, after the ADT of about 200 h, the performance of

t 3 Pd/S770 remains the same, while that of Pt/C-TKK drops signifi-

antly ( Fig. 3 (b)). The Nyquist plots at 200 mA cm

−2 are also tested.

132 F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140

Fig. 2. (a) TEM images of Pt/rGO–FCB; (b) Polarization curves of Pt/rGO–FCB and the conventional Pt/C electrode before and after ADT (I-V test: Pt loading 0.18 mg cm

−2 ,

65 °C, 0.05 MPa for both H 2 and O 2 ; ADT: Potential cycling from 0.6 V to 1.2 V vs. anode, sweep rate 100 mV s −1 , 30 °C, H 2 /N 2 for anode/cathode) [16] .

Fig. 3. (a) TEM image of Pt 3 Pd/S770 and (b) I-V curves using Pt/C-TKK and Pt 3 Pd/S770 as cathode catalyst before and after ADT (I-V Test: Precious metal loadings both are

0.5 mg cm

−2 for each cell; Electrode area 5 cm

2 , 85 °C, 35 mL min −1 /800 mL min −1 for H 2 /air at 0.2 MPa; ADT: Cycling current varies in the following sequences: 0 mA cm

−2

for 60 s, 200 mA cm

−2 for 60 s, 400 mA cm

−2 for 180 s, 300 mA cm

−2 for 60 s, 600 mA cm

−2 for 60 s and 200 mA cm

−2 for 60 s) [20] .

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The R ct of the single cell using Pt/C-TKK as the cathode catalyst

increased much more than that using Pt 3 Pd/S770 as the cathode

catalyst.

Because of the qualified performance and stability and simple

preparation process of Pt 3 Pd/S770, the catalyst is prepared on a

large scale and employed as the cathode catalyst for PEMFC stacks

in Sunrise Power Co., Ltd.

2.1.3. PtCo nanotube array catalyst

PtCo alloy is one of the most famous alloy catalysts for PEM-

FCs. The PtCo alloy catalysts have already been used in PEMFC

automobiles of Toyota and Honda. However, there are still some

drawbacks of PtCo alloy nanoparticle catalysts. Firstly, most of the

Pt atoms are under the surface, lowering the utilization ratio of

Pt. Secondly, the cheap metal on the surface is also easy to dis-

solve. What’s more, preparing MEAs with catalyst slurry requires

high control accuracy. Thin ordered electrode structure is a new

choice to reduce the Pt loading [22,23] . In the ordered electrodes,

the transportations of gas, electron and proton are improved by

the ordered channels, and the thin catalyst layer is beneficial for

removing the water generated. As a result, thin ordered electrodes

are considered to be the next generation electrodes with high per-

formance and low Pt loading.

Thin ordered electrodes based on open-tube PtCo alloy nan-

otube arrays are prepared at DICP employing highly ordered

Co–OH–CO 3 nanowire arrays as templates and cobalt sources

( Fig. 4 (a)) [24] . The ultrathin catalyst layer is prepared by hy-

drothermal and physical vapor deposition method. The open-

walled PtCo bimetallic nanotube arrays with a diameter ca. 100 nm

are directly aligned onto the PEM, forming an ultrathin catalyst

layer with a thickness ca. 300 nm. The incorporation of Co and

Pt is realized by a facile thermal annealing method, endowing

he catalyst layer with improved activity. During the purification

f catalyst-coated-membrane (CCM) electrode, the sealed off PtCo

anotubes cracks into open-walled nanotubes, making both the in-

erior and exterior surfaces expose to the surroundings. The cata-

yst layer is binder-free and beneficial for exposing catalytic active

ites, thus enhancing mass transport when the PEMFC works.

The PtCo nanotube arrays serving as the cathode are tested in

single fuel cell. With a cathode Pt loading of 52.7 μg cm

−2 , a

eak power density of 14.38 kW g Pt −1 is achieved, which is 1.7 fold

igher than that of the conventional CCM ( Fig. 4 (b)). Accelerated

egradation test manifests that the prepared nanostructured ultra-

hin catalyst layer is more stable than the conventional CCM.

.2. PEMs

.2.1. Cs x H 3- x PW 12 O 40 /CeO 2 as radical quenching agent for PEMs

The durability of proton exchange membrane (PEM) is one of

he key factors of PEMFC’s life [25] . To improve the durability of

EM, on the one hand, it is important to improve the antioxi-

ant ability of polymers themselves, such as eliminating hydrogen-

ontaining end groups and using support materials to improve the

echanical strength; on the other hand, radical quenching agent in

embrane is notable to eliminate radicals formed in ORR process

n situ, thus slowing down the degradation of PEMs. CeO 2 nanopar-

icles have already been widely used as radical quenching agent in

iological field. Babu et al. employs 5,5-dimethylpyrroline-N-oxide

DMPO) as the radical scavenger, and proves the fact of quenching

adical HO � by Electron Paramagnetic Resonance (EPR) [26] . How-

ver, CeO 2 nanoparticles are not proton conductive at low temper-

ture, resulting in a decrease of ionic conductivity after introducing

eO nanoparticles into PEMs.

2

F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140 133

Fig. 4. (a) SEM image of Pt-Co NTAs and (b) their performance in fuel cells (I-V Test: electrode area 2.56 cm

2 , 80 °C, gas flow rate 50/100 mL min −1 for H 2 /O 2 , relative

humidity 80%; The current density is normalized to the cathode Pt loadings) [24] .

Fig. 5. (a) TEM image of Cs x H 3 −x PW 12 O 40 /CeO 2 and (b) the FERs of Nafion, CeO 2 /Nafion and Cs x H 3- x PW 12 O 40 /CeO 2 -Nafion membranes [8] .

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Cs x H 3- x PW 12 O 40 /CeO 2 is employed as the radical quenching

gent for PEMs at DICP aiming to slow down the degradation

nd retain the proton conductivity because of the proton con-

uctivity of Cs x H 3- x PW 12 O 40 and the radical quenching properties

f CeO 2 . CeO 2 is prepared by a hydrothermal method, on which

s x H 3- x PW 12 O 40 with Keggin anionic structure is loaded by a

wo-step impregnation method [8] . The size of the supported

s x H 3- x PW 12 O 40 /CeO 2 is about 12 nm ( Fig. 5 (a)). The oxidative

egradation of Nafion membrane, Cs x H 3- x PW 12 O 4 0/CeO 2 -Nafion

omposite membrane and CeO 2 /Nafion composite membrane

re tested respectively with Fenton reagent at 80 °C, and the

uoride etching rates (FERs) of these membranes are com-

ared ( Fig. 5 (b)). The FERs of Cs x H 3- x PW 12 O 40 /CeO 2 -Nafion and

eO 2 /Nafion are significantly lower than that of Nafion membrane.

s x H 3- x PW 12 O 40 /CeO 2 in composite membranes can effectively

ecompose H 2 O 2 vice produced in PEMs and quench the radicals,

hus significantly improve the chemical stability of PEMs.

.2.2. CeO 2 modified PBI membranes for high temperature PEMFC

Polybenzimidazole (PBI) is one of the most ideal matrix

esins for high temperature PEMFCs because of its excellent me-

hanical and electrical properties over 100 °C. Polybenzimida-

ole/phosphoric acid (PBI/PA) PEM is one of the earliest studied

igh temperature PEMs, and the fuel cell employing PBI/PA mem-

rane gains satisfying performance. However, there are still some

hortcomings, such as phosphoric acid leakage, poor dimensional

tability and easily degradation of PBI polymers. Radicals such as

OH and �OOH are formed under operating condition of fuel cells.

he �OH often attacks the nitrogenous groups of PBI main chain,

nd the �OOH attacks the hydrocarbon bonds in benzene ring, thus

ggravating the degradation of PBI matrix and lead to a significant

ecline in power output of fuel cells.

PBI polymers with good solubility, high purity and moder-

te molecular weight are prepared by condensation of domestic

onomers at DICP to further synthesis the PBI membranes [27] .

onsidering the radical quenching properties of CeO 2 , PBI/CeO 2

omposite membranes with different CeO 2 loadings are prepared

y recasting method ( Fig. 6 (a)), and their electrochemical and an-

ioxidant properties are studied. Accelerating test in Fenton reagent

hows that the residue weight of PBI/CeO 2 membrane is higher

han that of PBI membrane, and with the more CeO 2 content in

BI/CeO 2 , the higher residue weight ( Fig. 6 (b)). The CeO 2 improve

he oxidation resistance of PBI membranes significantly. However,

he ionic conductivity of PBI membrane decreases with the in-

rease of CeO 2 , and the decrease of PBI in PBI/CeO 2 membrane is

till too high for fuel cell applications. Therefore, it is necessary to

ptimize the doping amount or fundamentally develop new mate-

ial for HT-PEMFCs.

.3. High-efficiency MEAs

.3.1. MEAs prepared by electrospinning

The structure of electrode significantly affects the performance

nd durability of the MEA in a fuel cell. Researches on electrode’s

tructure mainly focus on two aspects: (i) optimizing the three-

hase interface of the electrode to improve the utilization of elec-

rocatalyst and (ii) constructing the microchannels of the electrode

o improve the transportation efficiency of reactants and prod-

cts. Electrodes of nanofibers have good three-phase interface and

hree-dimensional interconnected microchannels, which are bene-

cial to improve the performance of the electrodes with low Pt

oading.

Electrospinning is a technology of drawing polymer solu-

ion/melt into nanofibers in a strong electric field. The diameter of

ontinuous fibers is from tens of nanometers to several microns.

rodt et al. prepare Pt/C nanofiber electrodes with electrospinning

echnology [28] . The ECSA reaches 114 m

2 g Pt −1 , which is 1.9

imes higher than that of traditional Pt/C catalyst. The power

ensity of Pt/C nanofiber electrode is 0.524 W cm

−2 with Pt

oading of 0.1 mg cm

−2 , which is higher than that of traditional

134 F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140

Fig. 6. (a) TEM image of PBI/CeO 2 and (b) the residue weight of PBI during the accelerating test in Fenton reagent (3 wt% H 2 O 2 , 4 ppm Fe 2 + , 80 °C).

Fig. 7. (a) SEM image of electrospinning electrode and (b) the performance in a single cell (H 2 /Air stoic: 1.5/4.5, anode Pt loading 0.2 mg cm

−2 , cathode Pt 0.25 mg cm

−2 ,

80 °C) [30] .

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Pt/C electrode even with a Pt loading of 0.4 mg cm

−2 . Yang et al.

fabricates ordered PtRu/C nanofiber electrodes by electrospinning

[29] . The ECSA of Pt in PtRu/C nanofiber electrodes is 1.5 times

higher than that of traditional PtRu/C electrodes, and the highest

power density of PtRu/C nanofiber electrodes for direct methanol

fuel cells is 1.4 times higher than that of traditional PtRu/C elec-

trodes with the same Pt loading. In addition, the Pt/C nanofiber

electrodes prepared by electrospinning often have better stability.

The electrospinning technology is also applied at DICP [30] . The

catalyst slurry is electrospinned onto an aluminum foil to form the

catalyst layer, then transferred to a PEM to form CCM electrode

( Fig. 7 (a)), and further hot-pressed with the gas diffusion layer to

form a MEA. The prepared electrodes are evaluated in single cells

with active areas of 25 cm

2 . The results show that the power den-

sity reaches 1.5 W cm

−2 with a Pt loading of 0.45 mg cm

−2 , or

0.3 mg Pt W

−1 ( Fig. 7 (b)). Although there is a certain gap compared

to the 2020 target of US DOE (0.125 mg Pt W

−1 ), the performance

of MEA is of great potential to be promoted by employing better

catalysts rather than commercial Pt/C.

2.3.2. MEAs prepared by spraying

In order to improve the performance of MEAs, the electrostatic

spraying process is also studied. Applying static charge to the cata-

lyst slurry and adjusting the potential between spraying head and

the base to finely control the spraying process, the loss of the

slurry dispersed into the air is notably reduced, improving the uti-

lization ratio of catalyst slurry. What’s more, the electrostatic force

can also improve the adhesion strength between the slurry and the

base, making the catalyst layer flat and uniform.

CCM is prepared by spraying catalyst slurry directly onto PEM.

The MEA is further formed by hot pressing the CCM with a gas

diffusion layer ( Fig. 8 (a)), and the performance in the single cell

is tested. Using 10 μm membrane from W. L. Gore & Associates,

nc. and commercial Pt/C catalyst with the anode Pt loading of

.1 mg cm

−2 and the cathode Pt loading of 0.2 mg cm

−2 , the peak

ower density of the MEA reaches 1.75 W cm

−2 ( Fig. 8 (b)), indicat-

ng that the preparation of MEAs by electrostatic spraying is valu-

ble for commercialization.

.4. Low-cost (CrN/Cr) 6 coated 316 L stainless steel bipolar plates

Bipolar plate is one of the key components of PEMFCs, whose

ost and life determines to some level the cost and life of PEMFC

tacks. The material of bipolar plate should be of high electrocon-

uctivity, corrosion resistance and stability under fuel cell’s operat-

ng conditions. In order to reduce the cost and increase the specific

ower of the stack, stainless steel-based bipolar plate has become

ne of the main choices. The poor corrosion resistance of stainless

teel bipolar plates is a problem. There are defects on the surface

f stainless steel, and local galvanic corrosion occurs at the defect

hen fuel cell works, which accelerates the corrosion to form pin-

oles. The pinholes on the surface of metal bipolar plates are usu-

lly prevented by preparing multilayer corrosion resistant films.

Since Fu prepared Cr x N coatings on 316 L to avoid the pinholes

n 2008 [31] , we have continuously focused on improving the cor-

osion resistance of metal bipolar plates and the electroconduc-

ivity [32,33] . 316 L stainless steel bipolar plate coated by multi-

ayer thin films consisting of CrN and Cr is also prepared at DICP,

amed (CrN/Cr) 6 /316 L SS ( Fig. 9 (a)). Basing on (CrN/Cr) 6 /316 L SS,

e design a type of bipolar plate with a working area of 670 cm

2

Fig. 9 (b)). The modified bipolar plates have excellent interfacial

onductivity, high corrosion resistance and durability. The inter-

acial contact resistance between (CrN/Cr) 6 /316 L SS bipolar plate

nd Toray carbon paper is 8.4–12.8 m � cm

2 under the pressure

f 0.8–1.4 MPa, which is 1–2 orders of magnitude lower than that

f metal bipolar plate without coatings ( Fig. 9 (c)). Meanwhile, the

F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140 135

Fig. 8. (a) SEM image of electrode prepared by spraying and (b) the performance of the MEA in the single cell (H 2 /air stoic: 2/3, RH 45%, 25 cm

2 , 90 °C, and 1.8 bar).

Fig. 9. (a) The multilayer coatings of CrN/Cr on 316 L SS, (b) 670 cm

2 (CrN/Cr) 6 /316 L SS bipolar plate, (c) its electroconductivity and (d) corrosion resistant compared to

316 L SS bipolar plate without coatings (70 °C, air saturated 0.5 M H 2 SO 4 + 5 ppm F −) [32] .

p

a

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v

n

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g

d

n

e

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l

P

2

2

i

w

t

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a

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c

h

f

t

b

t

−

s

o

d

r

a

f

p

c

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t

otentiostatic polarization experiments under simulated PEMFC

node and cathode conditions show that the corrosion resistance

f (CrN/Cr) 6 /316 L SS bipolar plates increases by 1–2 orders of

agnitude ( Fig. 9 (d)). In addition, the material to form CrN/Cr

oating is cheap, and the preparation process is simple and en-

ironmentally friendly. The flow field, metal sheet stamping tech-

ology and laser welding technology are also developed. The re-

ulted metal bipolar plate is 1 mm thick, containing an anode plate

ith the hydrogen flow field and a cathode plate with the oxy-

en flow field, and a water flow field between them. In our in-

ustrialization base, or Anhui Ming Tian Hydrogen Energy Tech-

ology Co., Ltd, full automatic generation line of fuel cell stacks

mploying metal bipolar plates have been established. Therefore,

his low-cost, high-electroconductive and corrosion-resistant stain-

ess steel-based bipolar plate has great potential for application in

EMFCs.

.5. Low-temperature and impurity air adaptability

.5.1. Research on cold storage/startup of stacks

The adaptability of PEMFCs to low temperature environment

s of great significance for the large-scale application. Liquid

ater helps in proton conduction of the PEM, but hinders the

ransport of reactants in GDL and flow fields. Icing of water at low

emperatures degrades the performance of PEMFCs or even re-

ults in a failure. Therefore, it is necessary to study the storage

nd startup of PEMFCs at low temperature. The key point is to

nderstand the relationship between the state of water and the

onductivity of the PEMs, and the effect of water content on the

eat capacity of the stacks [34] . The destination is to obtain a

easible and efficient strategy to store and startup the stack in low

emperature circumstance.

The study of low temperature storage/start-up of fuel cells has

een carried out in DICP [35,36] . An experimental platform is es-

ablished to simulate the low temperature environment as low as

40 °C. For cryogenic storage, the attenuation caused by −30 °Ctorage can be effectively avoided by blowing the free water out

f the fuel cell. The process is described as follows: after the shut-

own of the fuel cell, N 2 is purged into the stack until the internal

esistance reaches a plateau stage. The plateau stage is regarded as

sign that free water is completely exhausted. Then the stack is

rozen at −30 °C for a period of time, and is thawed at room tem-

erature after freezing. After that, the I-V curve and electrochemi-

al impedance of the stack are tested. Then the stack is shutdown

nd purged with N 2 again. The cycle of purge-freeze-thaw test is

arried out for 60 times. As can be seen from Fig. 10 (a), by remov-

ng the free water from the stack, the performance remains almost

he same for 60 cycles.

136 F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140

Fig. 10. (a) The I-V curves of the stack after freezing at −30 °C for different times and (b) the time dependence of the stack’s temperature when started at −40 °C.

Fig. 11. (a) The structure of the electrochemical air purifier and (b) its effect.

1

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2

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v

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a

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r

l

In order to realize low temperature start up, H 2 /air mixture re-

acts in the catalytic layer, releasing a large amount of heat to warm

the fuel cell up. Two mass flowmeters are used to accurately con-

trol the flux of air and H 2 , which are mixed in the pipeline and fed

into the cathode or anode of the fuel cell. When the temperature

of the fuel cell rises to a set value, the inlets of H 2 and air are both

switched to inert gas. After that, air and H 2 are fed into cathode

and anode respectively, and the fuel cell works. In the preheating

process, the mixture of H 2 and air is firstly fed into the anode for a

period of time, and then into the cathode to prevent the freezing of

water generated in the catalytic preheating process, which would

block the gas transport path. With this start up strategy, the fuel

cell can be started at −40 °C in about 60 s, which is about 10 °Clower than Toyota and Honda’ PEMFC stacks ( Fig. 10 (b))

2.5.2. Effects of SO 2 in the air

PEMFC uses ambient air as oxidant, and the air often contains

a certain amount of impurities such as CO, NO x and SO 2 . These

impurities can poison the catalyst even at very low concentration,

leading to degradation of performance, of which SO 2 has the most

significant damaging effect [37] . Therefore, it is of great signifi-

cance to study the influence of impurities in the air on the per-

formance of fuel cells and put forward corresponding solutions.

An electrochemical purifier is developed at DICP to eliminate

the SO 2 in the air. The anode of the electrochemical purifier is car-

bon felt coated with SO 2 oxidation catalyst and the cathode cat-

alyst is Pt/C. An external power supply provides potential for the

electrochemical purifier. The anode of the power supply is con-

nected with the anode of the purifier, and the cathode is connected

with the cathode of the purifier. Air containing a certain amount

of SO 2 passes through the anode of the purifier and then enters

cathode of the stack ( Fig. 11 (a)). The result is shown in Fig. 11 (b).

Without the purifier, 1 ppm SO 2 is directly fed into the fuel cell,

causing a voltage decrease from 0.683 V to 0.493 V within 50 h at

0 0 0 mA cm

−2 . As a contrast, the performance of the fuel cell re-

ains unchanged for 240 h with the purifier.

.6. Stacks and systems

.6.1. H 2 -PEMFC stacks at DICP

The stack is the heart of the fuel cell system. Large-scale com-

ercialized stacks should be competitive in terms of performance,

ife and cost. The route to improve the performance of fuel cell

tack includes improving the performance of catalyst and MEAs, re-

ucing the contact resistance of bipolar plate, designing appropri-

te gas flow field to promote transfer efficiency of gas and water,

nd improving the consistency of each single cell in the stacks. Re-

arkable progress has been made in stack technology in China and

broad. The most advanced stacks reported abroad have a volume

pecific power of 3.1 kW L −1 and a durability of 10,0 0 0 h. There are

lready more than 10,0 0 0 cars employing PEMFCs as the power

upply in Toyota, Honda and Hyundai, which are among the most

amous automobile enterprises around the world.

DICP masters a set of stack technology with wholly indepen-

ent intellective property right. The PEMFC stack of 50 kW using

tainless steel bipolar plates is fabricated at the beginning of 2018

ith a mass specific power of 2.0 kW kg −1 and a volume specific

ower of 3.0 kW L −1 , and the platinum dosage is 0.45 g Pt kW

−1

Fig. 12 (a) and (b)). The consistency of the stack is improved, with

he maximum amplitude of voltage 40 mV and a mean square de-

iation of 12 mV ( Fig. 12 (c)). The stack technology is still develop-

ng continuously at DICP, with the main concerns on reducing the

ost, improving the performance and life to enhance the competi-

iveness.

Local high potential ( > 0.85 V) often occurs in a fuel cell stack

t low load and startup/shutdown procedure. The high potential

ill accelerate the decay of catalyst support and membrane, thus

educing the durability of the PEMFCs. In order to prolong the

ife of fuel cell stack, it is important to prevent the hydrogen-air

F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140 137

Fig. 12. (a) 50 kW PEMFC stack in 2018, (b) performance and (c) consistence of the stack (100–110 kPa, 65 °C, utilization of circulating H 2 ∼90% without external humidity,

stoic air 2.5 with RH 60%), and (d) degradation of the stack with/without the shutdown strategy after 60 cycles of startup/shutdown.

Fig. 13. (a) PEMFC system for buses (2013) and (b) PEMFC system for cars (2018).

i

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2

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c

m

s

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t

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l

nterface when the stack starts and stops [38] . A shutdown strat-

gy for eliminating the hydrogen-air interface is developed at DICP.

he core procedures are as follows: when the stack stops, the air

s set to idle flow rate, and the hydrogen inlet and outlet valves

re closed at the same time. A resistor is used for self-discharge

f the stack. When the voltage of each single cell in the stack falls

elow 0.4 V, the hydrogen exhaust valve is opened and then the

outine procedures to shut the stack down are carried out. The

ydrogen-air interface is greatly weakened after lowering the open

ircuit voltage of each cell, thus preventing the rapid corrosion

f the catalyst layer at high voltage. The voltage decrease of the

tack with this strategy is about 1.47% at 500 mA cm

−2 after about

0 cycles of startup/shutdown, while without this strategy the

ecrease reaches 25.74% ( Fig. 12 (d)). Appropriate startup/shutdown

trategy can effectively slow down the attenuation and prolong

he service life of PEMFCs.

.6.2. PEMFC systems

Two generations of PEMFC system for automobiles are devel-

ped respectively in 2013 and 2018 at DICP. The system made in

013 ( Fig. 13 (a)) gains a power output from 50 to 150 kW with

n efficiency more than 50% at the rated working point, and the

tartup temperature is as low as −20 °C. The new generation stacks

roduced in 2018 with thin metal bipolar plate have a volume

epecific power 3.0 kW L −1 ( Fig. 13 (b)), and the power output of

he systems in 2018 is set to from 35 kW to 120 kW, with an en-

rgy efficiency more than 50% at the rated working point, and a

old start temperature as low as −40 °C.

Besides of H 2 /air PEMFCs, we also develop H 2 /O 2 PEMFCs. The

ajor works are on MEA and bipolar plates, stacks/modules and

ystems. The MEA is promoted on catalysts, PEMs and the prepar-

ng technologies. In order to increase the O 2 utilization, a water

ransport plate is designed and prepared to in-situ sweep out the

ater generated at the cathode, which is named “static drainage

echnology”. We have already assembled several 60 kW modules

nd systems employing this technology, and the H 2 /O 2 utilization

re both higher than 98%.

.6.3. Low cost fuel cells of next generation

Alkaline anion exchange membrane fuel cells are expected to

educe the cost of fuel cells considerably because of their poten-

ial of using non-noble metal catalysts [39,40] . At present, the re-

earch on AEMFCs mostly focuses on ionmers, membranes, cata-

ysts, MEAs and single cell. The highest power density of AEMFC

138 F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140

Fig. 14. (a) Kilowatt-level AEMFC system with Pt catalyst and (b) its performance (2014), (c) kilowatt-level AEMFC stack with Pt free catalyst and (d) its performance (2016).

Fig. 15. (a) PEMWE system with a H 2 production rate of 10 Nm

3 h −1 and (b) I-V curves at 0 MPa and 3.5 MPa.

2

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has reached 2 W cm

−2 with pure O 2 as the oxidant [41] . However,

the bad durability of AEMFCs and the lack in scaling up the key

components of the stacks make it not mature enough for commer-

cial application. The drawbacks also include the lack of stable com-

mercial membranes and resins, bad CO 2 adaptability, inadequate

research on water management and so on. As a result, there are

no publicly reported kilowatt-level AEMFC stacks and systems else-

where in China.

Basing on the homemade AEMs and ionmers, two kilowatt-level

AEMFC stacks respectively employing Pt catalysts and Pt free cata-

lysts are developed in DICP. The power output of Pt-based catalyst

stack exceeds 1 kW ( Fig. 14 (a) and (b)), and that of Pt free catalyst

stack reaches 920 W ( Fig. 14 (c) and (d)), which verifies the per-

formance and scaling-up feasibility of AEMFCs. By employing the

water transport bipolar plate to sweep out the water in anode, the

life of the AEMFC stacks reaches more than 500 h, indicating that

there is still a long way to go for commercial application.

.6.4. Progresses on proton exchange membrane water electrolysis

Producing hydrogen by water electrolysis is one of the key

ethods for large-scale utilization of renewable energy, and also

he premise of realizing green hydrogen economy and perfecting

reen hydrogen industry chain. Compared to the traditional al-

aline water electrolysis, proton exchange membrane water elec-

rolysis has the advantages of high efficiency, high gas purity and

ollution-free [42] .

The PEMWE technologies are also developed in DICP, including

he electrocatalysts and MEAs, the material and structure of bipo-

ar plates, and stacks and system [43–45] . Several PEMWE systems

re assembled with H 2 production rate of 10 Nm

3 h

−1 at 3.5 MPa

Fig. 15 (a)), and the energy consumptions are about 4.1 kWh Nm

−3

t the setting working point ( Fig. 15 (b)). PEMWE still has some

roblems to resolve, such as reducing the cost, improving energy

fficiency, raising the range of working current density and further

mproving the gas pressure.

F. Xie, Z. Shao and M. Hou et al. / Journal of Energy Chemistry 36 (2019) 129–140 139

Fig. 16. (a) First UAV powered by PEMFCs in China in 2012, (b) first manned aircraft powered by PEMFC in China in 2016 and (c) Ankai HFF6852G03FCEV fuel cell bus

employing 30 kW PEMFC system.

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.7. Recent application progresses

The PEMFC systems are used in unmanned aerial vehicle

UAV) to realize the first UAV flight powered by PEMFC in 2012

Fig. 16 (a)), and also used in manned aircraft to realize the

rst manned aircraft flight powered by PEMFC in China in 2016

Fig. 16 (b)). The thin metal bipolar plates, MEAs and fuel cell

tack technology have partly been authorized to Anhui Ming Tian

ydrogen Energy Technology Co., Ltd. for industrial production.

ully automated production lines of MEAs, metal bipolar plates

nd stack assemble lines have been established. The hydrogen-air

uel cell system is successfully applied in Ankai HFF6852G03FCEV

uel cell bus ( Fig. 16 (c)). At present, we are constructing pilot

cale-up bases for PEMFCs in Zhangjiagang, Jiangsu province and

alian, Liaoning province to promote the further industrialization.

. Conclusions

A relatively complete PEMFC industry chain has been formed in

hina, and the continuous expansion of PEMFC’s application will

ignificantly reduce the cost and improve the maturity. As one of

he earliest research institutes to develop PEMFC technology, DICP

ontinuously contributes to key materials, components, stacks and

ystems of PEMFC. In this paper, recent advances in H 2 -PEMFC at

ICP are introduced, including support materials, catalysts, PEMs,

EAs, bipolar plates, stacks, systems, AEMFCs, PEMWE and the ap-

lications. With the improvement of materials and components, as

ell as the optimization of stacks and control strategies, the cost

f fuel cell will be reduced and the performance and durability of

EMFCs will be further improved. The future work should focus

n reducing the cost by developing new materials, structures and

trategies of PEMFCs. And it is also important to strengthen the

nfrastructure construction of hydrogen production, transportation

nd filling.

cknowledgments

This work is supported by the National Key Research and

evelopment Program of China (2016YFB0101207), the Strategic

riority Research Program of the Chinese Academy of Sciences

XDB06050303 ) and the Natural Science Foundation of China

U1664259 ).

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