1. Non-platinum amorphous Fe60Co20Si10B10 cathode catalyst combined with anion selective binder for alkaline water electrolysis
M. Ďurovič, J. Hnát, C. I. Müller, T. Rauscher, L. Röntzsch, M. Paidar, K. Bouzek
Dep. of Inorganic Technology, University of Chemistry and Technology, Prague
Fraunhofer Institute for Manufacturing Technology and Advanced Materials, Dresden
Institute of Materials Science, Technische Universitat, Dresden

2. Introduction – Alkaline water electrolysis
25 – 30 wt.% KOH
70 – 80 °C
Cathode: Steel
4 H2O + 4 e- = 2 H2 + 4 OH-
Anode: Nickel
4 OH- = O2 + 2 H2O + 4 e-
Overall reaction
2 H2O = 2 H2 + O2
Separator
Asbestos, ceramics, composite materials
Long-term stability, non-platinum catalysts
Low efficiency, aggressive environment, limited flexibility
Scheme of industrial alkaline water electrolysis
Zeng, K.; Zhang, D., Recent progress in alkaline water electrolysis for hydrogen production and applications. Progress in Energy and Combustion Science 2010, 36 (3), 2

3. Introduction – Alkaline membrane water electrolysis
Alkaline zero gap arrangement
Diaphragm
Nonporous anion selective membrane
Selectively transports OH-
Porous electrodes
Ni mesh, tungsten
Catalysts
Anode: Spinel oxides, perovskites
Cathode: Ni/Fe-based alloys
Anion selective binder
Keeps catalyst particles on the surface of the electrode
Ensures the mechanical stability of the layer
Ensures the ionic conductivity in the catalytic layer
Higher efficiency and better flexibility
Stability of anion selective membranes, suitable catalytically active porous electrodes
Alkaline zero gap arrangement
Carmo M, Fritz DL, Mergel J, Stolten D. A comprehensive review on PEM water electrolysis. International Journal of Hydrogen Energy. 2013;38: 3

4. Aim of the work Porous cathode modified by a catalytic layer
Cathode catalyst
Amorphous Fe60Co20Si10B10 alloy
Anion selective polymer binder
poly(styrene-ethylene-butylene-styrene) (PSEBS) copolymer with 1,4-diazabicyclo[2.2.2]octane (DABCO) functional groups
Performance of the cathode catalytic layer with respect to:
Catalyst: Binder weight ratio (20:80, 50:50, 70:30, 80:20, 90:10)
Surface activation of the catalyst (Cyclic polarisation, leaching in KOH)
Long-term stability test (200 h, AWE conditions)
Anion selective polymer binder PSEBS-DABCO
Hnat, J., et al., Anion-selective materials with 1,4-diazabicyclo octane functional groups for advanced alkaline water electrolysis. Electrochimica Acta, : p 4

5. Experimental part – Fe60Co20Si10B10 alloy
Material
Fe, Co, Si, B
Fraunhofer Inst Mfg Technol & Adv Mat IFAM, Dresden, Germany
Production route
Gas atomization process  Ball milling (8 hours)  Amorphous powder
Properties
Good malleability
Simple preparation
Cheaper than Pt metals
Sufficient catalytic activity for hydrogen evolution reaction (HER)
Its catalytic activity is possible to increase by a suitable surface activation 5

6. Experimental part – Electrodes preparation
Cathode
Catalytic mixture: Fe60Co20Si10B10 catalyst + PSEBS-DABCO polymer binder
Support: Ni foam
Sedimentation of the catalyst on the Ni foam surface  Spraying of the binder on top of the catalyst
Anode
Catalytic mixture: NiCo2O4 + PSEBS-DABCO polymer binder
Spraying of the catalytic mixture on the Ni foam surface 6

7. Experimental part – Cathode catalyst activation
Cyclic polarisation
Ag/AgCl, KCl (sat.) ref. electrode
Ni counter electrode
Potential range: V to 0.2 V (vs. ref)
Scan rate: 100 mV s-1
Number of cycles: 20, 100 and 1000
1 mol dm-3 KOH solution, 25 °C
Leaching in KOH
1 mol dm-3 KOH, 25 °C
1, 4, 7 and 30 days 7

8. Experimental part - Methods
Scanning electrone microscopy
Morphology of prepared cathodes
Hitachi S4700
Accelerating voltage: 15 kV
Secondary electron detection
X-ray fluorescence
Elemental composition of as prepared and activated cathodes
Axios spectrometer (PANanalytical, Holland)
ICP-OES
Concentration of the individual elements of the catalyst released into the KOH solution after the surface activation
PerkinElmer® Optima™ 8000 spectrometer 8

9. Experimental part – Methods
Alkaline water electrolysis
10 wt.% KOH solution
Flow rate: 5 ml min-1
Polymer electrolyte: copolymer PSEBS with
trimethylamonium (TMA) functional groups
2-electrodes arrangement
Electrochemical impedance spectroscopy
Frequency range: 40 kHz – 1 Hz
Max. amplitude: 30 mV
Cell voltage: V
Equivalent electrical circuit.
L1 – Inductance of the wires; Rcell – Ohmic resistance of the cell resistance; Rc/Ra – Polarization resistance of cathode/anode; CPE1/CPE2 – Electrochemical double-layer capacitance of cathode/anode 9

10. R & D – Catalytic layer composition
10 wt.% KOH, 5 ml min-1, 50 °C
1.5 – 2 V, potential step: 0.05 V
Ni cathode:
20 mg Fe60Co20Si10B10 cm-2
PSEBS-DABCO binder
Ni anode:
5 mg NiCo2O4 cm-2
0.56 mg PSEBS-DABCO cm-2
Separator:
PSEBS-TMA polymer membrane 10

11. R & D – Catalytic layer compositionB C D F E
Catalyst: Binder weight ratio (20 mg cm-2)
A – Pure Ni foam
B – 20:80
C – 50:50
D – 70:30
E – 80:20
F – 90:10
High amount of binder (B,C)
Worse electron contact between the catalyst particles and Ni support
Insuficient amount of binder (E,F)
Worse three-phase contact for the catalyst particles
Formation of the relatively large agglomerates (white circle) of the catalyst particles
Optimal composition – 70:30 11

12. R & D – Cathode catalyst activation
XRF analysis
SEM analysis
ICP-OES
A – Fresh particle
B – Leaching in KOH
C – Cyclic polarisation
Element (wt. %)
Fresh electrode
Cyclic polarisation
Leaching in KOH Fe
38.806
32.169
37.904 Co
13.251
12.352
14.944 Si
0.764
0.466
0.456 B -
Element
(mg l−1) Fe Co Si B
Cyclic polarisation
n/A
0.116
0.044
Leaching in KOH
0.135
0.15 A B C 12

13. R & D – Activation by cyclic polarisation
10 wt.% KOH, 5 ml min-1, 50 °C
1.5 – 2 V, potential step: 0.05 V
Ni cathode:
15 mg Fe60Co20Si10B10 cm-2
6.5 mg PSEBS-DABCO binder
Ni anode:
5 mg NiCo2O4 cm-2
0.56 mg PSEBS-DABCO cm-2
Separator:
PSEBS-TMA polymer membrane 13

14. R & D – Activation by leaching in KOH
10 wt.% KOH, 5 ml min-1, 50 °C
1.5 – 2 V, potential step: 0.05 V
Ni cathode:
15 mg Fe60Co20Si10B10 cm-2
6.5 mg PSEBS-DABCO binder
Ni anode:
5 mg NiCo2O4 cm-2
0.56 mg PSEBS-DABCO cm-2
Separator:
PSEBS-TMA polymer membrane 14

15. R & D – Activation conclusion
10 wt.% KOH, 5 ml min-1, 50 °C
1.5 – 2 V, potential step: 0.05 V
Ni cathode:
15 mg Fe60Co20Si10B10 cm-2
6.5 mg PSEBS-DABCO binder
Ni anode:
5 mg NiCo2O4 cm-2
0.56 mg PSEBS-DABCO cm-2
Separator:
PSEBS-TMA polymer membrane 15

16. R & D – Long-term stability testC B A
A – Continuous activation of the catalyst and conditioning of the polymer electrolyte
B – Sorption of atmospheric CO2 / membrane degradation
C – Stabilization of the cell voltage
Addition of water 16

17. R & D – Long-term stability test
Rcell = Rmem + RKOH
Membrane degradation
Fresh membrane (1.22 mmol g-1)
After the stability test (1.1 mmol g-1)
Sorption of CO2
Decrease in membrane conductivity
Decrease in KOH conductivity
RC – Cathode polarization resistance
Constant values during the test
Values of cell ohmic resistance RCell and cathode polarization resistance Rc during the stability test.
Experimental conditions: Voltage – 1,8 V; separator – PSEBS-CM-TMA; anode – 5  mg NiCo2O4 cm−2 + 0.56 mg PSEBS-CM-DABCO polymer binder (4 cm2); cathode – 15 mg Fe60Co20Si10B10 cm−2 + 6,5 mg PSEBS-CM-DABCO cm−2 (3.8 cm2); electrolyte – 10wt.% KOH solution; flow rate – 5 ml min−1; temperature – 50 °C. 17

18. Conclusion
The combination of an Fe60Co20Si10B10 alloy and a PSEBS-DABCO binder represents a promising and cost-effective cathode catalyst system for alkaline water electrolysis
Optimal Catalyst: Binder weight ratio – 70:30
Both activations increased the activity of the catalyst by almost 50 %
Leaching in a KOH solution seems to be the optimal method considering the possible industrial application (simple, cost-effective procedure)
Catalyst remained stable and active during the long-term stability test 18

19. THANK YOU FOR YOUR ATTENTION