Method of conditioning an anion exchange membrane in an electrolysis cell

Abstract

A method of conditioning an anion exchange membrane (AEM) in an electrolysis cell is described. The anion exchange membrane (AEM) comprises non-hydroxide anions. The method comprises: providing an ele

Description

FIELD OF THE INVENTION The invention relates to a method of conditioning an anion exchange membrane in an electrolysis cell. BACKGROUND OF THE INVENTION Electrolysis of water using an anion exchange membrane (AEM) is known. Such electrolysis employs the use of a semipermeable membrane that conducts hydroxide ions (OH ), called an anion exchange membrane, between a pair of electrodes. Like a protonexchange membrane (PEM), an AEM separates the products, provides electrical insulation between electrodes, and conducts ions. In contrast to a PEM, an AEM conducts hydroxide ions rather than protons. The anion exchange membrane employed in conventional AEM electrolysis cells typically comprises a polymer having quaternary ammonium cations. Such a membrane is typically supplied with halide or bicarbonate counter-ions. Accordingly, in order to function as a hydroxide conductor, the membrane must be “conditioned”, during which the as-supplied counterions are replaced by hydroxide ions. Conventionally, this is achieved by soaking the AEM in a solution of NaOH or KOH for 24 to 48 hours, typically refreshing the hydroxide solution a number of times throughout. Exchanged membranes are stored in KOH or demineralised water before being installed onto the single-cell or stack whilst wet. The installation needs to be completed in a short time to minimise the carbonation reaction that occurs when the membrane in OH' form is exposed to the CO2 in the atmosphere. Furthermore, the membrane is installed into the electrolysis cell in a “swollen” form due to uptake of the alkaline solution. While this is acceptable for laboratory-scale research purposes, it is wholly undesirable for large-stack assembly because handling of a KOH-soaked membrane, or even of a water-wet membrane, in large quantities poses safety and practical issues. Performance issues, e.g. due to exposure to air, carbonation and swelling, also need to be considered when conditioning a membrane upon which one or more catalyst layers have been applied. For example, swelling in the x-y plane is an issue that can compromise the geometric area of the catalyst layers (resulting in an electrode area higher than the gas diffusion layer area and the geometric active area of the electrolysis cell), the homogeneity of the catalyst layers (causing cracking in the layers if the layers are less elastic than the AEM), and the catalyst loading at the cathode and anode (which will be lower than expected). As a consequence, the performance and stability of the catalyst-coated membrane in the electrolysis cell is negatively impacted. The present invention seeks to tackle at least some of the problems associated with the prior art or at least to provide a commercially acceptable alternative solution thereto. SUMMARY OF THE INVENTION One aspect of the present disclosure is directed to a method of conditioning an anion exchange membrane in an electrolysis cell, the method comprising: providing an electrolysis cell comprising an anode, a cathode and an anion exchange membrane situated between the anode and the cathode, the anion exchange membrane comprising non-hydroxide anions; and contacting the anion exchange membrane with a conditioning solution comprising hydroxide ions to replace at least some of the non-hydroxide anions with hydroxide anions. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a plot of current density against time during the conditioning of the anion exchange membrane of Example 1. Figure 2 shows a plot of cell potential against time during the conditioning of the anion exchange membrane of Example 2. DETAILED DESCRIPTION OF THE INVENTION In a first aspect, the present disclosure is directed to a method of conditioning an anion exchange membrane in an electrolysis cell, the method comprising: providing an electrolysis cell comprising an anode, a cathode and an anion exchange membrane situated between the anode and the cathode, the anion exchange membrane comprising non-hydroxide anions; and contacting the anion exchange membrane with a conditioning solution comprising hydroxide ions to replace at least some of the non-hydroxide amons with hydroxide amons. Each aspect or embodiment as defined herein may be combined with any other aspect(s) or embodiment(s) unless clearly indicated to the contrary. In particular, any features indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous. Surprisingly, by conditioning the anion exchange membrane in situ, swelling of the anion exchange membrane in the x-y plane, i.e. the plane perpendicular to the direction of anion flow between the cathode and anode during normal operation, may be inhibited. This may be because the membrane is conditioned while being mechanically constricted in the electrolysis cell. Advantageously, such inhibited swelling in the x-y plane may ensure that the geometric area of the catalyst layers remains substantially as designed, and the areaspecific catalyst loading at the cathode and anode will not vary to any great extent. In addition, the homogeneity of a catalyst layer present at the cathode and / or anode may not be compromised, therefore reducing the risk of cracking or delamination of such catalyst layers. This may be particularly important when conditioning a membrane on which one or more catalyst layers have been applied. Furthermore, any interaction of expanded catalyst layers with O-rings and other seals, which may cause loss of adhesion by physical erosion, may be substantially avoided. As a result, in comparison to conventional conditioning methods, the method of the present invention may result in a conditioned membrane that exhibits improved performance during operation of the electrolysis cell. While swelling in the x-y plane may be inhibited, swelling along the z-axis, i.e. perpendicular to the x-y plane, may occur during the in situ conditioning. However, such swelling along the z-axis may be beneficial since it may improve contact between the anion exchange membrane and the electrodes. Advantageously, by carrying out the conditioning in situ, one can avoid handling of the membrane while soaked in alkaline solution. In comparison to conventional conditioning methods, this may render the method easier to carry out and / or improve the safety of the method. The term “conditioning” as used herein may encompass rendering the anion exchange membrane in a form suitable for use in the electrolysis cell to convert water to hydrogen and oxygen. In other words, “conditioning” may encompass providing the anion exchange membrane with hydroxide ions, i.e. exchanging at least some of the non-hydroxide anions with hydroxide ions. The term “anion exchange membrane” or “AEM” as used herein may encompass a semipermeable membrane configured to conduct anions but minimise the transport of gases such as oxygen or hydrogen. The anion exchange membrane may be formed of ionomers. The term “electrolysis cell” as used herein may encompass a device capable of carrying out electrolysis. The electrolysis is typically carried out on water (which may include additives to improve conduction, such as an alkaline potassium salt) to form hydrogen and oxygen. The electrolysis cell comprises an anode, a cathode and an anion exchange membrane. The anion exchange membrane is typically in the form of a sheet. The sheet may have a thickness of, for example, from 20 to 150 pm, or from 30 to 100 pm. The anode and / or cathode may comprise a gas diffusion layer (GDL). A gas diffusion layer is sometimes referred to as a porous transport layer (PTL). The gas diffusion layer may be microporous, or may include microporous layer adjacent to the catalyst layer. The gas diffusion layer may take the form of, for example, a mesh (e.g. a nickel mesh), non-woven metal fibres and / or sintered metal. The gas diffusion layer may comprise, for example, nickel, nickel alloy and / or steel. Suitable gas diffusion layers are known in the art. The anode and cathode are electrically connected to each other and to a source of electricity to enable the electrolysis. So as to render the method more environmentally friendly, the electricity is preferably generated by renewable sources. The anode and / or cathode typically each comprises a bipolar plate. The bipolar plates are typically situated on the side of the anode or cathode opposite to that which faces the anion exchange material. The anion exchange membrane is situated between the anode and the cathode. The anion exchange membrane is typically in contact with the anode and the cathode. The anion exchange membrane is typically mechanically constricted within the electrolysis cell. For example, when assembled in a stack the membrane is typically clamped between two gas diffusion layers, which may make it harder for expansion in the x-y plane. The anode and anion exchange membrane are typically in contact via a catalyst layer. The catalyst layer is typically either applied to the membrane and pressed against the gas diffusion layer or applied to the gas diffusion layer and pressed against the membrane. As discussed in more detail below, the catalyst layer contacting the anode and anion exchange membrane may comprise an oxygen evolution reaction (OER) catalyst. Suitable OER catalysts are known in the art. The OER catalyst may promote the production of oxygen gas from OH' ions at the anode, i.e. 4OH' -+ 2H2O + O2 + 4e’ The cathode and anion exchange membrane are typically in contact via a catalyst layer. The catalyst layer is typically either applied to the membrane and pressed against the gas diffusion layer or applied to the gas diffusion layer and pressed against the membrane. As discussed in more detail below, the catalyst layer contacting the cathode and anion exchange membrane may comprise a hydrogen evolution reaction (HER) catalyst. Suitable HER catalysts are known in the art. The HER catalyst may promote the production of hydrogen gas from water at the cathode, i.e. 4H2O + 4e' -+ 4OH' + 2H2 Prior to conditioning, the anion exchange membrane comprises non-hydroxide anions. Typically, on a molar basis the majority of the anions contained in the anion exchange membrane prior to conditioning are non-hydroxide anions, preferably substantially all of the anions contained in the anion exchange membrane are non-hydroxide anions. Typically, at least 50 mol.% of the anions contained in the anion exchange membrane prior to conditioning are non-hydroxide anions based on the total moles of anions in the anion exchange membrane, more typically at least 60 mol%, 75 mol.%, even more typically at least 90 mol.%, still even more typically at least 95 mol.%, still even more typically at least 98 mol.%, still even more typically at least 99 mol.%. The method comprises contacting the anion exchange membrane with a conditioning solution comprising hydroxide ions. As discussed in more detail below, this typically involves contacting the anode and / or the cathode with the conditioning solution. The porous nature of the gas diffusion layers and catalyst layers enables the conditioning solution to pass through the anode and / or cathode to contact the anion exchange membrane. The conditioning solution is typically an aqueous solution. The contacting is carried out to replace at least some of the non-hydroxide anions with hydroxide anions. Typically, the contacting is carried out to replace substantially all of the non-hydroxide anions with hydroxide anions on a molar basis. For example, typically at least 75 mol.% of the non-hydroxide anions are replaced with hydroxide anions based on the total moles of anions in the anion exchange membrane, more typically at least 90 mol.%, even more typically at least 95 mol.%. The anion exchange membrane is preferably part of a catalyst coated membrane (CCM). The terms “catalyst coated membrane” or “CCM’ as used herein may encompass an anion exchange membrane having a catalyst layer situated on the anode-facing surface and / or the cathode-facing surface. In a preferred embodiment, the catalyst coated membrane comprises both a catalyst layer at an anode side (i.e. anode-facing side) and a catalyst layer at a cathode side (i.e. cathode-facing side). In an alternative preferred embodiment, the catalyst coated membrane comprises either: a catalyst layer at an anode side but not at a cathode side, the cathode comprising a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane; or a catalyst layer at a cathode side but not at an anode side, the anode comprising a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane. Such a CCM may be referred to as a % CCM. Preferably, the catalyst coated membrane comprises a catalyst layer at a cathode side but not at an anode side, the anode comprising a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane. Preferably, the anode comprises a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane, and the cathode comprises a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane. The catalyst layer at the cathode side or the catalyst layer of the gas diffusion layer of the cathode preferably comprises a hydrogen evolution reaction (HER) catalyst, more preferably a hydrogen evolution reaction catalyst comprising platinum, even more preferably a hydrogen evolution rection catalyst comprising platinum on a carbon support. Such catalysts may be particularly effective at generating hydrogen gas from water at the cathode. The catalyst layer at the anode side or the catalyst layer of the gas diffusion layer of the anode preferably comprises an oxygen evolution reaction (OER) catalyst, such as iridium oxide (IrOx), more preferably an oxygen evolution reaction catalyst comprising nonplatinum group metal, even more preferably an oxygen evolution reaction catalyst comprising an alloy and / or an oxide of one or more of nickel, manganese, cobalt, iron, and copper. Such catalysts may be particularly effective at generating oxygen gas from hydroxide ions at the anode. In addition, such catalysts may be lower cost in comparison to platinum group metal catalysts. In a particularly preferred embodiment, the anode comprises a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane, the catalyst layer comprising an OER catalyst comprising iridium oxide (IrOx) or an alloy and / or an oxide of one or more of nickel, manganese, cobalt, iron, and copper; and the catalyst coated membrane comprises a catalyst layer at a cathode side, the catalyst layer comprising a HER catalyst comprising platinum on a carbon support. This may provide enhanced membranecatalyst layer interaction, which may promote the desired electrochemistry. In an alternative preferred embodiment, the anion exchange membrane does not have a catalyst layer applied to it; the cathode comprises a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane; and the anode comprises a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane. The catalysts preferably correspond to the catalysts described above. Contacting the anion exchange membrane with a conditioning solution preferably comprises passing the conditioning solution to the anode and / or the cathode. More preferably, the conditioning solution is passed to both the anode and the cathode. As noted above, the porous nature of the gas diffusion layers of the anode and cathode and the catalyst layers may enable conditioning solution to pass through the anode and cathode to contact the anion exchange membrane. The non-hydroxide anions preferably comprise halide anions (e.g. Cf, Br', I') and / or bicarbonate (HCO3) anions. Commercial anion exchange membranes are typically supplied with such anions. The anion exchange membrane preferably comprises quaternary ammonium cations. Commercial anion exchange membranes typically contain such cations. The conditioning solution may comprise, for example, sodium hydroxide and / or potassium hydroxide. The conditioning solution preferably comprises potassium hydroxide. Potassium hydroxide is particularly suitable for exchanging non-hydroxide anions with hydroxide anions in the anion exchange membrane. The concentration of hydroxide ions in the conditioning solution is preferably from 0.1 to 2 M, more preferably from 0.5 to 1 M. Lower concentrations may result in inadequate and / or slow conditioning. Higher concentrations may increase the cost of the conditioning solution without any significant increase in the rate of conditioning and / or may cause corrosion of components of the electrolysis cell and / or may results in degradation to the membrane. The method preferably further comprises passing an electric current between the anode and the cathode while the anion exchange membrane is contacted with the conditioning solution. This may promote ion exchange and may increase the rate and / or extent of conditioning. The current preferably provides a current density of from 1 to 20 mAcm4, more preferably from 5 to 15 mAcm'1. Such current densities may result in particularly fast and / or extensive conditioning. The conditioning solution is preferably at a temperature of (i.e. contacts the anion exchange membrane at a temperature of) up to 80 °C, more preferably from 18 to 40 °C. Lower temperatures may result in slow and / or incomplete conditioning. Higher temperatures may increase the cost of the method without any significant increase in the rate or extent of conditioning. Furthermore, higher temperatures may result in corrosion of components of the electrolysis cell. The method preferably further comprises monitoring the extent of conditioning by monitoring a property of the electrolysis cell over time. When carrying out the conditioning in situ it is particularly useful to monitor the extent of conditioning. This is because, compared with conditioning a single anion exchange membrane ex situ in a vessel of alkaline solution, it is not always possible to predict how long it will take for in situ conditioning to complete. This may be because, when carrying out conditioning in situ, not all parts of the anion exchange membrane will be contacted with the conditioning solution to the same extent, for example due to the presence of catalyst layers or other components of the electrolysis cell. This may be particularly the case where the electrolysis cell comprises multiple anion exchange membranes in a stack. By monitoring the extent of conditioning, one can ensure that the conditioning is not carried out for longer than is needed. This may reduce the cost of the conditioning step by reducing the amount of conditioning solution that is required and / or the amount of current that is passed between the anode and cathode. This may also avoid any risk of starting operation of the electrolysis cell before the anion exchange membrane is fully conditioned, thereby reducing the performance of the electrolysis cell. Preferably, monitoring the extent of conditioning by monitoring a property of the electrolysis cell comprises monitoring the change in resistivity of the electrolysis cell over time and / or monitoring the change in concentration of non-hy dr oxide anions (e.g. halide or bicarbonate ions) in the conditioning solution over time. As the conditioning progresses, the resistivity of the electrolysis cell varies over time. This is due to, for example, an increase in the conductivity of the anion exchange membrane and / or a decrease in the conductivity of the conditioning solution as hydroxide ions are replaced with halide ions. As the conditioning progresses, the concentration of non-hydroxide anions (e.g. halide or bicarbonate ions) in the conditioning solution, originating from the unconditioned or partially conditioned membrane, increases over time. In a preferred embodiment, the change in resistivity is monitored by maintaining a current density profile and monitoring the change in the voltage, preferably wherein the current density profile comprises a constant current density or a stepped current density. In an alternative preferred embodiment, the change in resistivity is monitored by maintaining a voltage profile and monitoring the change in the current density, preferably wherein the voltage profile comprises a constant voltage or a stepped current density. In another alternative preferred embodiment, the change in resistivity is monitored by monitoring the open circuit voltage. Preferably, once the change in resistivity over time (the rate of change of resistivity) becomes less than 2% of an initial change in resistivity over time, the contacting of the anion exchange membrane with the conditioning solution is halted. This is because once the change in resistivity over time becomes less than 2% of an initial change in resistivity over time, this may indicate that sufficient anion exchange, i.e. conditioning, has taken place. Preferably, contacting the anion exchange membrane with a conditioning solution comprises passing the conditioning solution to the anode and / or the cathode, more preferably to both the anode and the cathode; passing the conditioning solution to the anode and / or the cathode comprises circulating the conditioning solution in a continuous loop; and the method further comprises monitoring the extent of conditioning by monitoring the resistivity of the conditioning solution. As conditioning progresses, hydroxide ions in the conditioning solution are replaced by non-hy dr oxide anions (e.g. halide or bicarbonate ions) from the anion exchange membrane. As a result, the resistivity of the conditioning solution increases. Preferably, during contacting the anion exchange membrane with the conditioning solution, additional hydroxide anions are added to the conditioning solution. This may ensure that the conditioning continues to progress as non-hydroxide anions in the membrane are replaced by hydroxide anions. Alternatively or in addition, the conditioning solution may be replaced with a fresh conditioning solution one or more times. In a further aspect, the present invention provides a method of monitoring the in situ conversion of an anion exchange membrane in an electrolysis cell from a non-hydroxide form to a hydroxide form, the method comprising: providing an electrolysis cell comprising an anode, a cathode and an anion exchange membrane situated between the anode and the cathode, the anion exchange membrane being in a non-hydroxide form; contacting the anion exchange membrane with a conditioning solution comprising hydroxide ions to convert the anion exchange membrane from the non-hydroxide form to a hydroxide form; and monitoring the extent of conversion by monitoring the resistance of the electrolysis cell. The advantages and preferable features of the first aspect apply equally to this aspect. The term “non-hydroxide form” as used herein may encompass a form in which the anion exchange membrane comprises non-hydroxide anions, as per the method of the first aspect. The term “hydroxide form” as used herein may encompass a form in which the anion exchange membrane comprises hydroxide anions, as per the method of the first aspect. In a further aspect, the present invention provides a method of monitoring the in situ conversion of an anion exchange membrane in an electrolysis cell from a non-hydroxide form to a hydroxide form, the method comprising: providing an electrolysis cell comprising an anode, a cathode and an anion exchange membrane situated between the anode and the cathode, the anion exchange membrane being in a non-hydroxide form; contacting the anion exchange membrane with a conditioning solution comprising hydroxide ions to convert the anion exchange membrane from the non-hydroxide form to a hydroxide form; and monitoring the extent of conversion by monitoring the resistance of the conditioning solution. The advantages and preferable features of the first aspect apply equally to this aspect. In a further aspect, the present invention provides a method of monitoring the exchange of non-hydroxide anions for hydroxide anions in an anion exchange membrane situated in an electrolysis cell, the method comprising: providing an electrolysis cell comprising an anode, a cathode and an anion exchange membrane situated between the anode and the cathode, the anion exchange membrane comprising non-hydroxide anions; contacting the anion exchange membrane with a conditioning solution comprising hydroxide ions to replace at least some of the non-hydroxide amons with hydroxide anions; and monitoring the extent of exchange by monitoring the resistance of the electrolysis cell. The advantages and preferable features of the first aspect apply equally to this aspect. In a further aspect, the present invention provides a method of monitoring the exchange of non-hydroxide anions for hydroxide anions in an anion exchange membrane situated in an electrolysis cell, the method comprising: providing an electrolysis cell comprising an anode, a cathode and an anion exchange membrane situated between the anode and the cathode, the anion exchange membrane comprising non-hydroxide anions; contacting the anion exchange membrane with a conditioning solution comprising hydroxide ions to replace at least some of the non-hydroxide anions with hydroxide anions; and monitoring the extent of exchange by monitoring the resistance of the conditioning solution. The advantages and preferable features of the first aspect apply equally to this aspect. The invention will now be described in relation to the following non-limiting examples. EXAMPLE 1 An electrolysis cell was provided having a catalyst coated membrane with a 2 mgirox cm'2 anode layer applied to the membrane and a 0.4 mgpt cm'2 cathode layer applied to the membrane. The membrane was a Fumasep® FAA-3-50 membrane having Br counter anions. Stainless steel GDL and current collector and Pt coated Ti flow mesh were used at the anode and the cathode. The membrane was conditioned by recirculating IM KOH flow for 24 hours at 25 °C at 40 ml / min. A voltage of 1.5 V was applied between the anode and cathode and the current density was monitored to monitor the extent of conditioning. The results are shown in Figure 1. As can be seen, the current density at 1.5 V decreases during the conditioning indicating increasing resistance. After the KOH is replaced at the end of conditioning the performance improves to expected current densities of ~ 10 mA cm’2 @ 1.5 V. Without being bound by theory, it is considered that the reduction in current density may be caused by an increase in the concentration of bromide ions in the feed solution causing an increase in resistance. The current density begins to flatten off indicating completion of OH' exchange. EXAMPLE 2 An electrolysis cell was provided having a catalyst coated membrane including a 2 mgirox cm'2 anode layer applied to the membrane and a 0.4 mgpt cm'2 cathode layer applied to the membrane. The membrane was a Fumasep® FAA-3-50 membrane having Br counter anions. Stainless steel GDL and current collector and Pt coated Ti flow mesh were used at the anode and the cathode. The membrane was conditioned by recirculating IM KOH flow for 16 hours at 40 °C under 40 ml / min. A current density of 10 mAcm'2 was applied between the anode and cathode and the voltage was monitored to monitor the extent of conditioning. The results are shown in Figure 2. As can be seen, the cell potential at 10 mA cm’2 increases during the 5 conditioning indicating increasing resistance. After the KOH is replaced at the end of conditioning the performance improves to expected current densities of ~10 mA cm'2 @1.5 V. Without being bound by theory, it is considered that the increase in cell potential may be caused by an increase in the concentration of bromide ions in the feed solution causing an increase in resistance. The potential does not flatten off indicating that conditioning may not 10 be complete. The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A method of conditioning an anion exchange membrane in an electrolysis cell the method comprising:providing an electrolysis cell comprising an anode, a cathode and an anion exchange membrane situated between the anode and the cathode, the anion exchange membrane comprising non-hydroxide anions; andcontacting the anion exchange membrane with a conditioning solution comprising hydroxide ions to replace at least some of the non-hydroxide anions with hydroxide anions.

2. The method of claim 1, wherein the anion exchange membrane is part of a catalyst coated membrane (CCM).

3. The method of claim 2, wherein the catalyst coated membrane comprises a catalyst layer at an anode side and a catalyst layer at a cathode side.

4. The method of claim 2, wherein the catalyst coated membrane comprises:a catalyst layer at an anode side but not at a cathode side, the cathode comprising a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane; ora catalyst layer at a cathode side but not at an anode side, the anode comprising a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane.

5. The method of claim 4, wherein the catalyst coated membrane comprises a catalyst layer at a cathode side but not at an anode side, the anode comprising a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane.

6. The method of claim 1, wherein:the anion exchange membrane does not have a catalyst layer applied to it;the cathode comprises a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane; andthe anode comprises a gas diffusion layer having a catalyst layer on a surface thereof facing the anion exchange membrane.

7. The method of any of claims 3 to 6, wherein the catalyst layer at the cathode side or the catalyst layer of the gas diffusion layer of the cathode comprises a hydrogen evolution reaction catalyst, preferably a hydrogen evolution rection catalyst comprising platinum, more preferably a hydrogen evolution reaction catalyst comprising platinum on a carbon support.

8. The method of any of claims 3 to 7, wherein the catalyst layer at the anode side or the catalyst layer of the gas diffusion layer of the anode comprises an oxygen evolution reaction catalyst, such as iridium oxide (IrOx), preferably an oxygen evolution reaction catalyst comprising non-platinum group metal, more preferably an oxygen evolution reaction catalyst comprising an alloy and / or an oxide of one or more of nickel, manganese, cobalt, iron, and copper.

9. The method of any preceding claim, wherein contacting the anion exchange membrane with a conditioning solution comprises passing the conditioning solution to the anode and / or the cathode.

10. The method of claim 9, wherein the conditioning solution is passed to both the anode and the cathode.

11. The method of any preceding claim, wherein the non-hydroxide anions comprise halide anions and / or bicarbonate anions.

12. The method of any preceding claim, wherein the anion exchange membrane comprises quaternary ammonium cations.

13. The method of any preceding claim, wherein the conditioning solution comprises potassium hydroxide.

14. The method of any preceding claim, wherein the concentration of hydroxide ions in the conditioning solution is from 0.1 to 2 M, preferably from 0.5 to 1 M.

15. The method of any preceding claim, wherein the method further comprises passing a current between the anode and the cathode while the anion exchange membrane is contacted with the conditioning solution.

16. The method of claim 15 wherein the current provides a current density of from 1 to 20 mAcm4, preferably from 5 to 15 mAcm4.

17. The method of any preceding claim, wherein the conditioning solution is at a temperature of up to 80°C, preferably from 18 to 40 °C.

18. The method of any preceding claim, wherein the method further comprises monitoring the extent of conditioning by monitoring a property of the electrolysis cell over time.

19. The method of claim 18, wherein monitoring the extent of conditioning by monitoring a property of the electrolysis cell comprises monitoring the change in resistivity of the electrolysis cell over time and / or monitoring the change in concentration of nonhydroxide anions in the conditioning solution over time.

20. The method of claim 19, wherein the change in resistivity is monitored by maintaining a current density profile and monitoring the change in the voltage, preferably wherein the current density profile comprises a constant current density.

21. The method of claim 19, wherein the change in resistivity is monitored by maintaining a voltage profile and monitoring the change in the current density, preferably wherein the voltage profile comprises a constant voltage.

22. The method of claim 19, wherein the change in resistivity is monitored by monitoring the open circuit voltage.

23. The method of any of claims 19 to 22, wherein once the change in resistivity over time becomes less than 2% of an initial change in resistivity over time the contacting of the anion exchange membrane with the conditioning solution is halted.

24. The method of any of claims 1 to 19, wherein:contacting the anion exchange membrane with a conditioning solution comprises passing the conditioning solution to the anode and / or the cathode, preferably to both the anode and the cathode;passing the conditioning solution to the anode and / or the cathode comprises circulating the conditioning solution in a continuous loop; andthe method further comprises monitoring the extent of conditioning by monitoring the resistivity of the conditioning solution.

25. The method of any preceding claim, wherein during contacting the anion exchange membrane with the conditioning solution, additional hydroxide anions are added to the conditioning solution.

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