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Catalyst coated membrane for zero-gap alkaline water electrolyzer

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Presentation on theme: "Catalyst coated membrane for zero-gap alkaline water electrolyzer"— Presentation transcript:

1 Catalyst coated membrane for zero-gap alkaline water electrolyzer
Jaromír Hnát, Michaela Plevová, Jan Žitka, Karel Bouzek Department of Inorganic Technology University of Chemistry and Technology Prague

2 Hydrogen and hydrogen economy
Hydrogen as energy vector produced from renewable sources energy storage – alternative to batteries water as side product Renewable sources Water electrolysis Electricity production

3 Alkaline vs. Proton Exchange Membrane water electrolysis

4 Alkaline membrane water electrolysis
Membrane electrode assembly (MEA) decrease the KOH concentration differential pressure is possible lower operational temperature membrane membrane diaphragm standard setup anion selective membrane zero gap arrangement catalyst coated membrane anion selective membrane, ionomer binder and catalyst

5 Experimental part – polymer synthesis
Synthesis in three steps synthesis of the back bone polymer block copolymer of styrene-ethylene-buthylene-styrene (PSEBS) chloromethylation 5 wt.% liquid solution in chloroform was prepared -> polymer binder introduction of the functional groups 1,4-Diazabicyclo[2.2.2] octane (DABCO)

6 Experimental part – temperature characterization
TGA/DSC measurement Linseis STA PT 700 LT device temperature stability determination glass transition temperature identification Ion exchange capacity measurement measured by UV/VIS spectroscopy membranes treated: under air atmosphere in Cl- cycle at 20 – 200 °C for 24 hours mechanical changes and stability

7 Experimental part – CCM preparation
Catalyst synthesis NiCo2O4 as anode catalyst NiFe2O4 as cathode catalyst prepared by coprecipitation of the nitrates by NaOH calcined at 325 °C (NiCo2O4) and 475 °C (NiFe2O4) nickel cobalt iron oxygen Ion exchange capacity measurement air-brush spraying technique polymer substrates PSEBS-CM PSEBS-CM-DABCO ink composition mixture of catalyst and binder in CHCl3 ratio catalyst:binder equal to 9:1 catalyst load 2.5 or 10 mg cm-2

8 Experimental part – CCM characterization
Scanning electron microscopy Hitachi S4700 scanning electron microscope morphology and interface contact of the layers Alkaline water electrolysis load curves measurement: cell voltage – 1.5 – 2.0 V liquid electrolyte – 1 – 15 wt.% KOH temperature – 45 °C electrode area – 4 cm2 galvanostatic test conditions of the load curves measurement 250 mA cm-2; 20 hours electrochemical impedance spectroscopy frequency range – 65 kHz – 1Hz; cell voltage 1.8 V

9 Results – temperature characterization
TGA/DSC Chemical stability measurement stability of the backbone polymer up to 420 °C stability of the functional groups up to 200 °C no glass transition temperature no changes in IEC up to 120 °C degradation of the functional groups at 200 °C

10 Results – first steps PSEBS-CM-DABCO PSEBS-CM
Temperature: 45 °C; liquid electrolyte flow rate: 5 ml min-1; anode – 10 mg NiCo2O4 cm-2, cathode – 10 mg NiFe2O4 cm-2, concentration of the liquid electrolyte indicated in the inset of the figure, Ni foam as substrate, geometrical area 2 x 2 cm2

11 Results – first modification
Alkaline water electrolysis Dependence of the cell voltage on the time of alkaline water electrolysis using different MEAs (shows in figures inset) at current density 250 mA cm-2. Geometrical area of the electrode 4 cm2, temperature 45 °C, concentration of the liquid electrolyte 10 wt.%, electrolyte flow rate 5 ml min-1.

12 Results – first modification
Morphology Fig. A – 2.5 mg catalyst cm-2 fresh CCM Fig. B – 2.5 mg catalyst cm-2 used CCM Fig. C – 10 mg catalyst cm-2 Fig. D – 10 mg catalyst cm-2 Fig. E – bare Ni foam Fig. F – 10 mg catalyst cm-2 fresh CCE CCM used for load curve measurement in 10 wt.% KOH at 45 °C in the cell voltage range 1.5 – 2.0 V with additional 20 hours at current density 250 mA cm-2.

13 Results – PSEBS usage Alkaline water electrolysis load curves
Temperature: 45 °C; liquid electrolyte flow rate: 5 ml min-1; anode – 10 mg NiCo2O4 cm-2, cathode – 10 mg NiFe2O4 cm-2, concentration of the liquid electrolyte indicated in the inset of the figure, Ni foam as substrate, geometrical area 2 x 2 cm2

14 Results – PSEBS usage Alkaline water electrolysis electrochemical impedance spectroscopy Values of the system resistance and polarization resistance on KOH concentration evaluated from EIS spectra measured under the conditions of the alkaline water electrolysis at 1.8 V cell voltage.

15 Results – PSEBS usage Alkaline water electrolysis load curves
Dependence of the cell voltage on the time of alkaline water electrolysis using different MEAs (shows in figures inset) at current density 250 mA cm-2. Geometrical area of the electrode 4 cm2, temperature 45 °C, concentration of the liquid electrolyte 10 wt.%, electrolyte flow rate 5 ml min-1.

16 Results Stable catalyst coated membrane was prepared for the first time for alkaline water electrolysis. CCM MEA with catalyst loading 2.5 mg cm-2 showed the comparable performance to CCE MEA with catalyst loading 10 mg cm-2. Vital influence of the catalytic layer thickness on the performance alkaline water electrolysis observed. Further optimization of the catalytic layer composition and preparation is needed.

17 Thank you for your attention
Financial support of this research by Ministry of the Industry and Trade of the Czech Republic under project No. FV10529 is gratefully acknowledged.


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