ALKALINE WATER ELECTROLYSIS MEMBRANE DEVELOPMENT ...
Transcript of ALKALINE WATER ELECTROLYSIS MEMBRANE DEVELOPMENT ...
W. JU, M. HEINZ, D. BURNAT, C. BATTAGLIA,
U. F. VOGT*
EMPA
MATERIALS SCIENCE AND TECHNOLOGY
MATERIALS FOR ENERGY CONVERSION
CH-8600 DÜBENDORF
SWITZERLAND
ALKALINE WATER ELECTROLYSIS: MEMBRANE DEVELOPMENT & CHARACTERIZATION
~ 1800 : Electrolytic Water splitting (Ritter, Nicholson, Carlisle)
1834 : First use of the term «electrolysis» by Faraday
1900 : Oerlikon (Zürich) introduces first bipolar electrolyzer (2.5 V)
1939 : First 10’000 Nm3/h (900kg/h) electrolyzer
1949 : Zdansky pressure electrolyzer for Lonza
1951 : First commercial 30 bar electrolyzer (Lurgi)
1967 : Zero-Gap Design
HISTORY OF WATER ELECTROLYSIS: KNOWN FOR OVER 200 YEARS
Lurgi-Zdansky prototype
alkaline electrolyser, 1949
Hydrogen Report Switzerland 2010/2011
Water electrolysis accounts for ca. 5% of hydrogen production
Most of hydrogen is used on side for the production of
Ammonia (Haber Bosch Process)
Conversion of heavy petroleum sources by hydrocracking
Cooling of generators
steel & glass manufacturing
Diaphragm to separate H2 and O2,
conduction of OH- via KOH
in open pore network
Working conditions: 32 bar, 85°C, 25wt% KOH
Production rate: 760 m³/h H2 , equ. to 3.3 MWel
Energy Consumption: 4,3 - 4,6 kWh/m³ H2
H2 purity: 99.8 - 99.9 vol%, O2 purity: 99.3 - 99.6 vol%
556 cells, cell =1.6 m, length: 12 m, weight: 90 t
100 installed units worldwide Souorce: IHT 8th International Symposium Hydrogen & Energy, 16.-21. February 2014, Zhaoquing, China
Electrolyser , Giovanola SA, Monthey, CH, Sapphire production
1) bipolar plates
2) electrode meshes
3) separator membrane
4), 5) H2 and O2 ducts
6) electrolyte ducts
Source: Svein Sunde, NTNU, Trondheim, Halder Topse Catalysis Forum, 2006
Zero-gap geometry
Alkaline Water Electrolysis:
H2O H2 + ½ O2
ALKALINE WATER ELECTROLYSIS
Materials and system development:
Developing diaphragms with high ionic conductivity
Using highly active electrocatalysts for the OER and HER
Avoiding surface blockage by generated gas bubbles
ALKALINE WATER ELECTROLYZER
𝜺𝟐𝟓°𝑪
= 𝟏.𝟐𝟑 𝑽
𝑬𝒄𝒆𝒍𝒍
Energy loss:
Ionic resistance (membrane, KOH)
Activation energy
Gas-bubble resistance
Electronic resistance
E
I
DIAPHRAGMS FOR ALKALINE
ELECTROLYSER
Alkaline Water Electrolysis
High OH- conductivity via KOH in open pore
network during gas production
Chemical and mechanical stability
separator thickness (2.5 mm)
operating temperature (max. 85)
c(KOH) (25wt% - 35wt%)
Asbestos is banned by law since 1990
REPLACEMENT OF ASBESTOS DIAPHRAGMS
diaphragm to separate H2 and O2
Conduction of OH- via KOH in open pores
Zero-gap geometry
56% porosity of Asbestos
membrane Mg3Si2O5(OH)4
Mg3Si2O5(OH)4 Chrysotile Asbestos CaSiO3 Wollastonite (Mg,Fe)2SiO4 Olivine BaSO4 barite 99% purity
www.webmineral.com
BaTiO3 98% purity, perovskite str., electroceramics ZrO2 3YSZ (TOSOH), technical ceramics, SOFC
Synthetic based fillers
Mineral base fillers
ALTERNATIVE HYDROPHILIC FILLER MATERIALS
MINERALS AS FILLER: THERMODYNAMIC MODELING (GEMS)
Low pH: congruent dissolution
High pH: (a, b, c) Si ions increases , Ca, Mg drops precipitation of portlandite & brucite
Barite shows higher stability, no secondary phases formed
Calculations of the
influence of pH on the
concentration of different
Ions for:
a) wollastonite
b) forsterite
c) Chrysotile
d) Barite
@ 85°C, pH 9.6 - 13
The equilibrium phases are
indicated by gray and orange bars
Corrosion Experiments of Mineral Fillers, 85°C, 25 wt% KOH
Concentrations of Si, Mg, Ca, and Ba leached from forsterite, wollastonite, chrysotile and barite
in 5.5 M KOH solution at 85 C as a function of time.
Dotted lines represent the logarithmic function, drawn as a guide to the eye only.
Burnat et al. Journal of Power Sources 291 (2015) 163-172
concentration of ions from leaching experiments, measured by ICP-OES
relative mass loss of leached minerals
(Mg-Olivine)
MEMBRANE PRODUCTION BY PHASE INVERSION
2. tape casting (Si-Coated PET film or weaved reinforcement)
1. polysulfone + filler particles + solvent
Polysulfone + BaSO4 (barite) + NMP
3. Phase inversion process – immersion precipitation in H2O coagulation bath
Source: Membranes for Membrane Reactors, John Wiley & Sons, Ltd, 2011.
Phase inversion – Process in which polymer solution is converted into two phases:
- Solid polymer rich phase (rigid structure) - Polymer lean phase (pores)
Membrane thickness:
0.2 – 1.5 mm
CONTINUOUS PILOT DIAPHRAGM PRODUCTION @ CILANDER
Manufacturing of 0.4 m width diaphragm
Source: Burnat et al. Composite membranes for alkaline electrolysis based on polysulfone and mineral fillers, Journal of Power Sources, (291), 2015, pp.163-172
(I) – skin layer; polymer rich,
quite dense, develops first
(gas separation properties)
(II) – bulk microstructure;
very porous, less polymer,
develops after the skin layer,
mainly mechanical properties
MICROSTRUCTURAL FEATURES OF THE MEMBRANE
CAPILLARY FLOW POROMETRY
Liquid (Porofil) membrane
P
N2
Sketch of the measuring cell for CFP (capillary flow porometry )
Defines pore size distribution of percolating pores (effective for the mass transport)
The higher the BP pressure – the better the physical gas separation
a) differential flow distribution through the percolating pore network
b) determination of the largest, medium and smallest pore sizes for various membranes located within the top layer
Source: Burnat et al. Composite membranes for alkaline electrolysis based on polysulfone and mineral fillers, Journal of Power Sources, (291), 2015, pp.163-172
𝑅𝑀 = 𝑅𝐸+𝑀 − 𝑅𝐸
𝜌𝑀 =
1
𝐾𝐸+𝑀−
1
𝐾𝐸 𝐿𝐸+𝑀
𝐿𝑀+
1
𝐾𝐸 Ω𝑐𝑚
where KE+M is the conductivity including the membrane, KE conductivity without membrane, L the distance between the electrodes, LM the thickness of the membrane
Measured as zero-bias, provides a fingerprint of electrical performance of the membrane
ZERO-BIAS RESISTIVITY MEASUREMENT
a) Schematic representation of top layer (Lt) and bulk microstructure (Lb) ratios for membranes of
various thicknesses
b) Influence of membrane thickness on total resistivity
Ratio between the skin layer and bulk microstructure changes variation in resistivity
Top skin layer has resistivity 2 orders of magnitude higher!
Source: Burnat et al. Composite membranes for alkaline electrolysis based on polysulfone and mineral fillers, Journal of Power Sources, (291), 2015, pp.163-172
𝜌𝑀 = (𝑹𝒕+𝑹𝒃)𝐴
𝐿𝑀=
𝝆𝒕𝑳𝒕 + 𝝆𝒃(𝐿𝑀 − 𝑳𝒕)
𝐿𝑀= 𝝆𝒃 + (𝝆𝒕 − 𝝆𝒃)
𝑳𝒕
𝐿𝑀
ρ = 5 Ω·cm
VARIATION OF TOTAL RESISTIVITY AS A FUNCTION OF THICKNESS
Good electrical performance and high bubble points can be achieved
MEMBRANE POROSITY VS. RESISTIVITY
Source: Burnat et al. Composite membranes for alkaline electrolysis based on polysulfone and mineral fillers, Journal of Power Sources, (291), 2015, pp.163-172
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54 56 58 60 62 644.0
4.5
5.0
5.5
6.0
To
tal p
oro
sity / %
NMP / vol%
a)
me
mb
rane
resis
tivity
cm
Porosity / %
M14
M16
M21
b)
(Zirfon)
influence of NEP content on porosity influence of porosity on resistivity
- Zirfon 500utp membrane as reference
Determined by the Zero-bias resistivity measurement method
Nitidor Pilot Electrolyser, 0.2 Nm3/h, 5 cells, 117 mm
Voltammetric results of Barite based Diaphragms
LAB-SCALE 1 CELL ELECTROLYSER
LAB-SCALE ALKALINE WATER ELECTROLYSER
• Lab-scale Electrolyser
• Specifications:
• Pressure: 30 bar
• Temperature: 80 °C
• Electrode area: 19.6 cm2
• Current density: 500 mA/cm2
• Complete in-house development
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LAB-SCALE ALKALINE WATER ELECTROLYSER
LAB-SCALE ALKALINE WATER ELECTROLYSER
Electrolysis cell
LabVIEW interface
For electrolyser adjustment: Diaphragm: Zirfon 500utp Electrodes: Nickel plates
LAB-SCALE ALKALINE WATER ELECTROLYSER
Voltammetric curves measured with Zirfon 500utp diaphragm and Nickel plates
Pressure effect on cell voltages
30 °C increasing pressures
80 °C increasing pressures
Pressure effect on cell voltages not very pronounced
LAB-SCALE ALKALINE WATER ELECTROLYSER
Voltammetric curves measured with Zirfon 500utp diaphragm and Nickel plates
Temperature effect on cell voltages
1 bar increasing temperature
30 bar increasing temperature
Temperature effect on cell voltages very pronounced
SUMMARY & OUTLOOK
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Chemical stable membrane based on polysulfone & BaSO4 filler
Top surface layer significantly contributes to membrane resistivity ~2 orders of magnitude higher than bulk.
Labscale electrolyser suitable for electrode & membrane characterization
Ongoing work: electrode- and catalyst development
CTI Project NMAE: New membranes for Alkaline Electrolysis
SI/50076
European Project ELYGRID, FCH-JU: High Pressure Alkaline
Electrolysis
BFE P&D Project PALE: Laboratory alkaline electrolyser test
bench for high pressure and temperature
Swiss electric project: Alkaline Electrolysis for renewable
energy generation: Membrane Development for Industrial
Electrolyser
ACKNOWLEDGEMENT
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© Daimler
THANK YOU FOR YOUR ATTENTION!
FOR A SUSTAINABLE FUTURE