HT-XAFS for Elucidating the Formation Mechanisms of ORR
Active Sites in Fe-N-C Electrocatalysts
A. Mufundirwa,1 K. Ogi,2 S. Yoshioka,2,6 T. Sugiyama,6 G. F. Harrington,7,9 K.
Sasaki,1,5,7 A. Hayashi,1,8 S. M. Lyth5,8,10*
1Department of Mechanical Engineering; 2Department of Applied Quantum
Physics and Nuclear Engineering, 6Research Centre for Synchrotron Light
Applications (RCSLA); 8Platform of Inter/Transdisciplinary Energy Research(Q-PIT), Kyushu University.
Iron-decorated nitrogen-doped carbon (Fe-N-C) catalysts could replace platinumin fuel cells. However, there is lack of understanding of the formation mechanismsof active sites in these materials. Here, we utilise a nitrogen -doped carbon foam
support with optimised porosity, surface area, and condu ctivity. This is infiltrated
with iron (II) acetate and heat treated, changing the chemical state of theadsorbed iron, whilst the support properties are relatively unchanged. Hightemperature X-ray adsorption spectroscopy (XAS) was used to observe changes in
the adsorbed iron in-situ during synthesis, revealing the transition from Fe -Obonds in FeAc at low temperature to Fe-N bonds at 700 C as the iron binds withnitrogen atoms in the support. At 900

C Fe-Fe bonds are observed as the iron is

reduced to metal, forming carbon-encapsulated nanoparticles. These physicalchanges significantly affect the electrochemical activity.

- 69 -HT-XAFS for Elucidating the Formation Mechanisms of ORR Active Sites
in Fe-N-C Electrocatalysts
Mufundirwa,1 K. Ogi,2 B. Smid,3 B. V. Cunning,4 Y. Shundo,5 S. Yoshioka, 2,6 T. Sugiyama,6 G. F. Harrington,7,9 K. Sasaki,1,5,7 A. Hayashi,1,8 S. M. Lyth5,8,10*A.

1Department of Mechanical Engineering, Kyushu University, 2 Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University,
3Charles University, Prague, Czech Republic, 4UNIST, Ulsan, Republic of Korea, 5 International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University

NEXT-FC

6 Research Centre for Synchrotron Light Applications (RCSLA), Saga Light Source, Kyushu University Beamline BL06, Saga Light Source, Tosu, Japan,
7Next-Generation Fuel Cell Research for Hydrogen Energy, Kyushu University, 8Platform of Inter/Transdisciplinary Energy Research (Q-PIT), Kyushu University,

Next-Generation Fuel Cell Research Center

9Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA., 10Energy 2050, University of Sheffield, UK

Introduction

1. (a)

1. (c)

1. (b)(PEFCs)(Pt/C)

Pt/C(Fe-N-C)

New Ballard fuel cell stackwith Nissinbo Fe-N-C catalyst(ORR)(Pajarito Powder Ballard

1. (d))

Fe-N-Cand /orFe-N-C
Fe-N-CUp to 45% of fuel cell costcomes from the platinum
catalyst!

-Fe-N-C proposed active sites

Fe-N-C Catalyst

Figure 1: (a) PEFC schematic, (b) Pt/C to Fe-N-C schematic (c) Commercial Fe-N-C systems (d) Proposed active sites

Support Synthesis
2. (a)

Iron-Decoration

2g15 gN-C1000 CN2N2

2. (b)

FeAc Adsorption

Na + N[CH2CH2OH]3

N[CH2CH2O-Na+]3 + 3/2 H2Figure 2: (a) Schematic diagrams of N-C support, and (b) Fe-N-C synthesis procedures.

(TEA)
NaOH
22(FeAc)

1000
N-C

Results
3. (a)

N-C
150

1. BET and XRD

3505007009002(NH3/N2)

2. XPS and EXAFS
4. (a)

N-CFeAc-N-C
Fe-N-C300

400300

N 1s

N-C
FeAc-N-C
Fe-N-C900

Fe-N(O)

4. (b)

300

Heat Treatment (RT-900 ºC)

3. Transmission electron microscopy
Fe-C

Fe-Fe

Fe-Fe

7

5.

900 oC

6.5
6250

5Fe-N-C700

150

700 oC

5.5

Fe-N-C500

200

700 oC

4.5

Fe-N-C900
410 408 406 404 402 400 398 396 394 392

50Fe 2p

3.5

500 oC

30

2.5
0.0

0.2

0.4

0.6

0.8

1.0

300 oC

2

Relative Pressure (p/po)

3. (b)

Carbon-encapsulated Fe-nanoparticles

4100

1.5

150 oC

1N-C
Fe-N-C900
NPC-20000.5Binding Energy (eV)

-Fe(011)-Fe(002)

RT

0740 735 730 725 720 715 710 705 700 695

C(002)

012345Atomic Fe (Porphyrin-like)
6Radial distance (A)4. Electrochemical Characterization

6. (a)

Figure 4: (a) N 1s and Fe 2p XPS, and (b) EXAFS-Fe(112)6. (b)

0108XPSFeAc

N-C

0.1 M HClO450 mV/s

6-1

41020304050

607080902

Figure 3: (a) BET of N-C and Fe-N-C samples, and (b)XRD of N-C, Fe-N-Cs and commercial Fe-N-C sample.

FeAc 150~300 C
Fe-N
300~700 C
700 C
Fe-N-30.

-2-4-5-6

XRD

0Fe-N-C900 N-C

N-C

0.6500 C

Fe-N-C

0.8

11.2-60.2

0.4

0.60.8Potential (VRHE)

1Fe-N-C

ORR

700 C

References(1600 m2/g )
PGM

(N-C)
ORR
Fe

Fe-N-C

0.4

Figure 6: (a) CVs and (b) LSVs of Fe-N-C samples

FeAc

Conclusions:0.2

Potential (VRHE)

Fe-N-C900

FeAc-N-C
Fe-N-C300
Fe-N-C500
Fe-N-C700
Fe-N-C(NH3)900-4-8

N-C Fe-N-C I
FeAc
Fe-N-C700

0.1 M HClO4
10 mV/s-2

2700 C

ORR
Fe-N

ORR

NAP-XPS MössbauerUIIn-Situ XAFSKyudai
HR-TEM
FIB-SEM
Taro,2007
MEA- 70 -1.

Platinum-decorated nitrogen-doped graphene foam electrocatalysts, J. Liu, T. Daio, K. Sasaki, S. M. Lyth, Fuel Cells 14, 728 (2014)

2.

Defective Nitrogen-Doped Graphene Foam: A Metal-Free, Non-Precious Electrocatalyst for the Oxygen Reduction Reaction in Acid, J. Liu, T. Daio, D. Orejon, K.
Sasaki, S. M. Lyth, J. Electrochem. Soc. 161 (4), F544-F550 (2014)

3.

Solvothermal Synthesis of Nitrogen-Containing Graphene for Electrochemical Oxygen Reduction, S. M. Lyth, Y. Nabae, N. M. Islam, T. Hayakawa, S. Kuroki, M.
Kakimoto, S. Miyata, eJ. Surf. Sci. & Nanotech., 10, 29-32 (2012)

4.

Strickland, K. et al. Nat. Commun. 6:7343 (2015).

5.

Identification of catalytic sites for oxygen reduction in iron- and nitrogen-doped graphene materials, A. Zitolo, V. Goellner, V. Armel, M.-T. Sougrati, T. Mineva, L.
Stievano, E. Fonda, and F. Jaouen Nat. Mater., vol. 14, no. 9, pp. 937 42, 2015.

6.

Metal-Free Nitrogen-Doped Carbon Foam Electrocatalysts for the Oxygen Reduction Reaction in Acid Solution,J. Liu, S. Yu, T. Daio, M. S. Ismail, K. Sasaki, and S. M.
Lyth, J. Electrochem. Soc., vol. 163, no. 9, pp. F1049 F1054, 2016.

7.

F. Jaouen, J. Herranz, M. Lefèvre, J.-P. Dodelet, U. I. Kramm, I. Herrmann, P. Bogdanoff, J. Maruyama, T. Nagaoka, A. Garsuch, J. R. Dahn, T. Olson, S. Pylypenko,P. Atanassov, and E. A. Ustinov, ACS Appl. Mater. Interfaces, 2009, 1, 1623 39..

8.

http://www.gizmag.com/daihatsu-gets-greative-with-three- concepts-fortokyo/20477/pictures#8

9.

http://www.greencarcongress.com/2016/01/20160127-hzb.hmlt

1.2