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EP-4735193-A1 - POROUS TRANSPORT LAYER

EP4735193A1EP 4735193 A1EP4735193 A1EP 4735193A1EP-4735193-A1

Abstract

A method for manufacturing a porous transport layer for use in a PEM electrode, comprises the steps of: providing a first powder having a first grade, and a second powder having a second grade, wherein the second grade of the second powder is finer than the first grade of the first powder; blending together the first and second powders; and constructing a porous construct by compacting together and sintering the blended powder; wherein the first grade of the first powder is selected such that the porous construct has a constant fluid transfer rate in use, and the second grade of the second powder is selected so as to produce enhanced fluid transfer properties in a surface-adjacent region of the porous construct in use.

Inventors

  • MARCHAL, FREDERIC ANDRE
  • BACKHOUSE, Rachel

Assignees

  • ITM Power UK Limited

Dates

Publication Date
20260506
Application Date
20240628

Claims (15)

  1. 1. A method for manufacturing a porous transport layer for use in a PEM electrode, comprising the steps of: providing a first powder having a first grade, and a second powder having a second grade, wherein the second grade of the second powder is finer than the first grade of the first powder; blending together the first and second powders; and constructing a porous construct by compacting together and sintering the blended powder; wherein the first grade of the first powder is selected such that the porous construct has a constant fluid transfer rate in use, and the second grade of the second powder is selected so as to produce enhanced fluid transfer properties in a surface- adjacent region of the porous construct in use.
  2. 2. The method of claim 1, further comprising the step of locally compacting the surface-adjacent region of the porous construct.
  3. 3. The method of claim 2, wherein the surface-adjacent region is compacted by rolling.
  4. 4. The method of claim 2 or 3, wherein the porous construct is re-sintered following compaction.
  5. 5. The method of any previous claim, wherein the fluid transfer rate is evaluated by measuring, over a period of time, a volume of a volume of water exiting the porous construct.
  6. 6. The method of any preceding claim, wherein the first powder has particle sizes of 80 pm or more, and the second powder has particle sizes of less than 80 pm.
  7. 7. The method of claim 6, wherein the first powder comprises powder sizes between 85 pm and 125 pm, and the second powder comprises powder sizes between 35 pm and 75 pm.
  8. 8. The method of any preceding claim, wherein the blended powder comprises at least 90% the first powder by mass.
  9. 9. A porous transport layer for use in a PEM electrode, comprising a porous construct; wherein the porous construct is constructed by compacting together and sintering a blend of a first powder and a second powder, the first powder having a first grade and the second powder having a second grade, wherein the second grade of the second powder is finer than the first grade of the first powder; and wherein the first grade of the first powder is selected such that the porous construct has a constant fluid transfer rate in use, and the second grade of the second powder is selected so as to produce enhanced fluid transfer properties in a surface- adjacent region of the porous construct in use.
  10. 10. A method for selecting a first grade of a first powder for use in manufacturing of a porous transport layer for use in a PEM electrode, the method comprising steps of: a) providing a plurality of sample powders each having a distinct sample powder grade; b) selecting a sample powder having an initial sample powder grade; c) manufacturing a sample porous construct by compacting together and sintering the sample powder; d) evaluating a fluid transfer rate of the sample porous construct; e) if the fluid transfer rate of the sample porous construct is constant, identifying the initial sample powder grade as the first grade of the first powder; f) if the water transfer rate of the sample porous construct is not constant, selecting a coarser sample powder grade from the plurality of sample powders; and g) repeating steps c-f iteratively until a sample powder grade is found from which a sample porous construct with a constant water transfer rate can be manufactured.
  11. 11. The method of claim 10, wherein the fluid transfer rate is evaluated by measuring a water transfer rate of the sample porous construct.
  12. 12. The method of claim 11, wherein measuring the water transfer rate comprises measuring, over a period of time, a volume of a volume of water exiting the porous construct.
  13. 13. The method of claim 12, wherein the period of time is at least 1000 hours.
  14. 14. A method for selecting a second grade of a second powder for use in providing enhanced water transfer properties in the surface-adjacent region of a porous transport layer for use in a PEM electrode, the porous transport layer being formed from a first powder having a first grade selected such that the porous construct has a constant water transfer rate in use, the method comprising steps of: a) providing a plurality of sample powders each having a distinct sample powder grade; b) selecting a sample powder having an initial sample powder grade, wherein the initial sample powder grade is finer than the first grade of the first powder; c) forming a sample blended powder by blending the sample powder together with the first powder; d) manufacturing a sample porous construct by compacting together and sintering the blended powder; e) evaluating fluid transfer properties in a surface-adjacent region of the sample porous construct; f) if the fluid transfer properties of the surface-adjacent region of the sample porous construct are enhanced, identifying the initial sample powder grade as the second grade of the second powder; g) if the water transfer properties of the surface-adjacent region of the sample porous construct are not enhanced, selecting smaller sample powder grade from the plurality of sample powders; and h) repeating steps c-g iteratively until a sample powder grade is found from which a sample porous construct with a constant water transfer rate can be manufactured.
  15. 15. The method of any of claims 10 to 15, wherein selecting the second powder further comprises characterising the porosity of the sample porous construct.

Description

POROUS TRANSPORT LAYER BACKGROUND TO THE INVENTION Hydrogen is emerging as a pivotal player in the pursuit of decarbonizing industries and achieving the goal of net-zero emissions. Its significance lies in its potential to act as a pristine and adaptable energy carrier, allowing a diverse range of industries and modes of transport to become more sustainable. Hydrogen offers a tangible solution for industries heavily reliant on fossil fuels, such as transportation, manufacturing, and power generation. Through the substitution of carbon-intensive fuels with hydrogen, these sectors can substantially diminish their carbon footprint. Hydrogen fuel cells emerge as a promising alternative to conventional internal combustion engines, as they solely emit water vapor and efficiently generate electricity. Hydrogen enables the integration of renewable energy sources into existing energy systems. Surplus electricity stemming from renewable sources, such as wind and solar power, can be harnessed to produce hydrogen via electrolysis. This process facilitates energy storage and mitigates the intermittency challenges associated with renewable power, ensuring a dependable and steadfast energy supply. Hydrogen produced via electrolysis from renewable energy sources is known as green hydrogen because no greenhouse gas is emitted (in contrast to other methods of producing hydrogen, such as from natural gas). Hydrogen can be produced using PEM (proton exchange membrane) electrolysis. This method is in essence the reverse of a fuel cell. Water is passed through an electrically charged PEM electrode, which splits the water into hydrogen and oxygen. Unlike other methods of hydrogen production, PEM electrolysis does not produce carbon-dioxide or greenhouse gas as a by-product. The membrane is impermeable to gases ensuring safety and is able to self- pressurise gases produced at each electrode. This, however, requires a finely tuned electrode/membrane interface. Additionally, PEM electrolysis can be powered by renewable energy sources such as wind turbines. As a result, PEM electrolysis can be used to produce hydrogen with very low carbon emissions. PEM electrolysis is typically performed by passing water through an electrochemical cell and applying a direct-current (DC) voltage at two electrodes: a negatively charged cathode and positively charged anode, separated by a gas impermeable proton exchange membrane. The membrane is coated by a catalyst layer on one or both sides. Water is oxidised giving protons and oxygen at the anode, the protons are transferred through the proton exchange membrane and are then reduced at the cathode with electrons, producing hydrogen. The protons (positively charged hydrogen ions) pass through the ion transport membrane (a solid polymer electrolyte -PEM) to the cathode, where they combine with electrons to form molecular hydrogen. The molecular hydrogen, in gaseous form, can then be collected at pressure. A porous transport layer (PTL) is positioned between the membrane and the anode and/or cathode, in order to manage the flow of water to the membrane. However, existing systems and methods for PEM electrolysis have drawbacks. Electrolysis is expensive, as electrical power must be supplied to the electrolyser to perform the reaction. Electricity may be wasted by efficiency losses inside the electrolyser. In addition, the rate of hydrogen production from electrolysis may be slow compared to other forms of hydrogen production, such as from natural gas. Accordingly, there exists a need for PEM electrolysis systems which provide increased efficiency and reduce overall costs. SUMMARY OF THE INVENTION According to a first aspect, there comprises a method for manufacturing a porous transport layer for use in a PEM electrode, comprising the steps of: providing a first powder having a first grade, and a second powder having a second grade, wherein the second grade of the second powder is finer than the first grade of the first powder; blending together the first and second powders; and constructing a porous construct by compacting together and sintering the blended powder; wherein the first grade of the first powder is selected such that the porous construct has a constant fluid transfer rate in use, and the second grade of the second powder is selected so as to produce enhanced fluid transfer properties in a surface-adjacent region of the porous construct in use. PTLs can be the source of significant inefficiencies. In PEM electrolysis, for long life, good water saturation of the catalyst layer is required, especially at maximum operating regime. PTLs can limit performance and reduce the lifetime of PEM water electrolysers. Inefficiencies can arise from impaired transport of reactant and products to and from active reaction sites, which is difficult to detect. These transports take place in opposite direction at the anode and in the same direction in the case of the cathode within the PTL. Over time, initial