A method for activating an electrolysis cell or a co 2 electrolytic device, an activated electrolysis cell and an activated co 2 electrolytic device

Abstract

A method for activating an electrolysis cell or an electrolytic device, the method comprising providing an electrolysis cell or an electrolytic device comprising one or more electrolytic cells, preferably comprising a membrane electrode assembly, providing a power supply connected to the electrolysis cell(s) to activate the electrolytic cell, operating the power supply while monitoring the current density, and applying an activating reverse current treatment to the electrolysis cell and / or applying an activating reverse potential treatment to the electrolysis cell. An activated electrolysis cell, and an activated electrolytic device for reducing carbon dioxide to products, the electrolytic device comprising one or more activated electrolysis cells, and a power supply for providing electric current to the electrolysis cells.

Description

[0001] A method for activating an electrolysis cell or a CO2 electrolytic device, an activated electrolysis cell and an activated CO2 electrolytic device

[0002] Field of the application

[0003] The present application relates to a method for activating an electrolysis cell or a CO2 electrolytic device. The present application also relates to an activated electrolysis cell and to an activated CO2 electrolytic device.

[0004] Background

[0005] It has been generally recognized that CO2 emissions causing global warming can be converted into useful product such as hydrocarbons or CO using CO2 electrolytic devices. CO can be used as a reactant for example for Fischer- Tropsch synthesis to produce liquid hydrocarbons.

[0006] However, the prior art materials and methods have problems in the selectivity of electrochemical methods used for converting CO2 to a desired product. Recent investigations have demonstrated that there is need for efficient and fast methods for activating membrane electrode assemblies (MEA), especially in zero gap CO2 electrolyzers. Typically, an electrolyzer performance increases until the required stable plateau. Without a suitable activation, it can take the electrolyzer a very long time, for example from several hours to days if not more, to reach required performance, depending on the MEA. The prior art activation methods are complex and may for example require special and often lengthy treatment cycles.

[0007] Examples of prior art activation methods typically include applying combination of one or more of electrochemical potentiostatic or galvanostatic polarization, overpotentials, short-circuiting, cyclic voltammograms / voltammetries (CVs) as well as external methods, such as elevating temperature or pressure and the use of activating reagents or recovery gas. The prior art methods may be destructive to the electrolytic cells and potentially effecting the overall lifetime of the MEA.

[0008] There is a need for activating, enhancing and prolonging the function and efficiency of devices comprising electrolysis cells. For example, it would be desirable to recover the function of electrolytic devices and to provide a nondestructive activation method. Summary

[0009] In the present invention it was found out how to overcome drawbacks of prior art and how to avoid using the methods of prior art. A simple and effective electrolytic / potentiostatic / galvanostatic two step procedure as disclosed herein was developed to activate CO2 electrolyzers to achieve rapid activation and subsequent stabilised performances. The activation method was successfully demonstrated on electrolyzers comprising a membrane electrode assembly (MEA), such as based on copper (Cu), silver (Ag) or AgCu alloy cathodes, and an iridium oxide (IrCh) anode separated by an anion exchange membrane.

[0010] The present activation method (A) was compared to representative methods commonly described in prior art, such as LSVs (method (B)) and CVs (method (C)), to demonstrate the effectiveness of activation method A. In addition, the method A was further demonstrated to recover the performance of the electrolyser previously not activated, in a control experiment.

[0011] The present disclosure provides a method for activating an electrolysis cell or an electrolytic device, the method comprising

[0012] -providing an electrolysis cell or an electrolytic device comprising one or more electrolytic cells,

[0013] -providing a power supply connected to the electrolysis cell(s) to activate the electrolytic cell,

[0014] -optionally flowing anolyte and catholyte through the electrolysis cell(s) prior to activation,

[0015] -operating the power supply while monitoring the current density,

[0016] -optionally measuring open circuit potential of the electrolysis cell(s), and

[0017] -applying an activating reverse current treatment to the electrolysis cell, which reverse current is reverse to the current of the normal operation of the cell, and / or -applying an activating reverse potential treatment to the electrolysis cell, which reverse potential is reverse to the potential of the normal operation of the cell.

[0018] The present disclosure also provides an activated electrolysis cell for reducing carbon dioxide to one or more products, the activated electrolysis cell comprising a membrane electrode assembly comprising -an anode, -a cathode, and -an ion exchange membrane between the anode and the cathode, wherein the electrolysis cell has been activated with the method.

[0019] The present disclosure also provides an activated electrolytic device, such as a CO2 electrolytic device for reducing carbon dioxide to one or more products, the electrolytic device comprising

[0020] -one or more activated electrolysis cells, and

[0021] -a power supply for providing electric current and / or potential to the electrolysis cells.

[0022] The present disclosure also provides a method for converting, such as reducing, carbon dioxide to products, such as to hydrocarbons, alcohols, carboxylic acids and / or to CO, the method comprising

[0023] -providing the activated electrolysis cell, or the activated electrolytic device, -providing a source of carbon dioxide,

[0024] -supplying the carbon dioxide to the activated electrolysis cell or to the activated electrolytic device,

[0025] -applying electric current and / or potential to the anode and the cathode to provide electrolysis to electrocatalytically reduce the carbon dioxide to generate products, and

[0026] -separating and / or recovering the generated products, such as one or more of hydrocarbons, alcohols, carboxylic acids and CO.

[0027] The main embodiments are characterized in the independent claims. Various embodiments are disclosed in the dependent claims. The embodiments and examples recited in the claims and in the specification are mutually freely combinable unless otherwise explicitly stated. Examples not in the scope of the claims are examples useful for understanding the invention.

[0028] The present activation method significantly reduces the initial surge in potential and time required for the performance to stabilise at the desired potential. It can be used to recover the performance of electrolyzer that has not been activated. It is possible to easily activate or regenerate an existing electrolytic device to obtain an activated or regenerated electrolytic device.

[0029] The present activation method can be applied to cathodes with variety of catalysts. It was found out that the present activation method is especially suitable for cathodes with catalyst layers comprising or consisting of copper (Cu), silver (Ag), silver-copper (AgCu) alloy, preferably in the form of nanoparticles, such as with particle sizes around 20 nm.

[0030] The activation procedure is simple and fast and not specific to the electrolyzer area. The activation is scalable and can be performed with cells of various sizes, as the activation treatment modifies MEA perpendicular to the MEA plane. All the variables, such as potential and initial concentration of reactants, across the cell area remain the same. The activation can be performed at room temperature and at ambient pressure.

[0031] As the present activation method is non-destructive, it enhances the durability of the electrolysis cell and electrolytic device.

[0032] The activation method described herein can be performed whilst both anolyte, such as KHCO3 solution, and humidified CO2 as catholyte are flowing through the electrolyzer. No activating agents or other gaseous input streams, such as N2, are needed, or even desired.

[0033] Brief description of the figures

[0034] Figure 1 shows a graph demonstrating Activation method A applied on silver (Ag) based cathode. The preferred activation method comprises an initial positive linear sweep voltammetry (LSV) applied from the open circuit potential (OCP) to 3.4 V with little increase in current density. A second sweep from -2 V to 3.4 V with an onset in current density at 2.3 V. Activation using method A was applied to the failed non-activated sample.

[0035] Figure 2 shows a graph demonstrating corresponding potential vs time performance at 200 mAcm-2of the Ag electrolyzer using Activation method A. Following the reactivation using method A, the performance, at constant current density of 200 mA cm-2was recovered at a stable potential of 3 V within a minute.

[0036] Figure 3 shows a graph demonstrating Activation method B on Ag based cathode. Sweep rate was 5-10 mVs’1. Four consecutive positive LSVs were applied from the OCP up to 6 V with current cut-off at 200 mAcirr2. The first two LSVs achieve current densities below 50 mAcirr2at 6 V, and the second two LSVs reached 200 mAcirr2at around 5 V with an initial onset potential at 2.3 V. Figure 4 shows a graph demonstrating corresponding potential vs time performance at 200 mAcm-2run on Ag electrolyzer following activation method B. The performance of the electrolyser at a constant current density of 200 mAcm-2proceeds with an initial surge in potential followed by a dip and then a gradual increase in potential. The initial stabilisation takes up to an hour before a potential of around 5 V is achieved which exceeds the desired potential limit of 3 V.

[0037] Figure 5 shows a graph demonstrating corresponding Activation method C on Ag based cathode. Sweep rate was 5-10 mVs’1. Cyclic voltammetries (CVs) were applied from OCP to an upper limit of 3.4 V and a lower limit of -2.0 V for a total of twenty cycles. The CVs indicate the decrease in evolution of a reduction wave and an oxidation wave at around -1 V and 0.25 V, respectively. The on-set potential occurs at 2.2 V. A total of 20 redox cycles were applied.

[0038] Figure 6 shows a graph demonstrating corresponding potential vs time performance at 200 mAcm-2of Ag electrolyzer following activation using method C. The performance of the electrolyser at a constant current density of 200 mAcirr2proceeds with an initial surge in potential to a value of 3.5 V before reducing back down to steady value of around 3.2 V within 10 minutes. A noticeable increment in the potential can be observed towards 3.25 V the end of the test run.

[0039] Figure 7 shows a graph demonstrating potential vs time performance of an Ag electrolyzer at 200 mAcm-2with no activation. In the absence of any activation method, the electrolyser exceeds 10 V within the first minute under a current density of 200 mAcirr2and the performance testing was subsequently stopped.

[0040] Figure 8 shows a graph demonstrating Activation method A on copper (Cu) based cathode. The same activation method A was used to successfully activate Cu based cathode.

[0041] Figure 9 shows a graph demonstrating the potential vs time performance at 200 mAcirr2of Cu electrolyzer. The overall poor stability, with respect to the increase in voltage, is an inherent characteristic of Cu catalysts.

[0042] Figure 10 shows a graph demonstrating Activation method A on a AgCu alloy based cathode. The activation proceeds with similar response to both Cu and Ag counterparts. Figure 11 shows a graph demonstrating the potential vs time performance at 200 mAcm-2of the AgCu alloy.

[0043] Figure 12 shows an exemplary single cell electrolyzer configuration (12A), a cathode GDE structure (12B) and a setup comprising an electrolyzer connected to a potentiostat / power supply (12C), as used herein. The legends are: 1. Cathode flow field plate, 2. Anode flow field plate, 3. Polymer Electrolyte Membrane, 4. Cathode gasket, 5. Anode gas diffusion electrode (GDE), 6. Cathode gas diffusion electrode (GDE), 7. Anode gasket, 8 / 9. Flow channels, 10. Inlet for catholyte, 11. Outlet for anolyte, 12. Outlet for catholyte and gaseous products, 13. Inlet for anolyte, 14. Cathode electrical connection point, 15. Anode electrical connection point. 16. Membrane electrode assembly (MEA), 17. GDE composition, 18. Macrofibrous layer, 19. Microporous layer, 20. Catalyst layer, 21. Electrolyzer, 22. Potentiostat / power supply, 23. Computer, and 24. Electrical wires.

[0044] Figure 13 shows a process flow diagram of a process including the activation method A.

[0045] Figure 14 shows a graph demonstrating Activation method A applied on silver (Ag) based cathode of a larger 250 cm2electrolyzer cell. The activation method comprises an initial positive linear sweep voltammetry (LSV) applied from the open circuit potential (OCP) to 3.4 V with little increase in current density. A second sweep from -2 V to 3.4 V with an onset in current density at 2.3 V.

[0046] Figure 15 shows a graph demonstrating corresponding potential vs time performance at 200 mAcm-2of the larger 250 cm2Ag electrolyzer using Activation method A. Following the reactivation using method A, the performance was run continuously for 50 hours with a stable potential around 3.6 V at a constant current density of 200 mAcm2.

[0047] Detailed description

[0048] In this disclosure, percentage values, unless specifically indicated otherwise, are based on weight (w / w, by weight, or wt%). If any numerical ranges are provided, the ranges include also the upper and lower values. In specific examples the embodiments or examples specified with the open term “comprise” may be further limited with a closed term “consisting of’. The diameters disclosed herein, such as particle size, unless specifically indicated otherwise, refer to the smallest diameter, and may be average diameter, which may be number-average diameter, and may be determined microscopically, such as by electron microscopy. Disclosed dimensions or other features may be measured by image analysis of microscope images, such as images from a field emission scanning electron microscope (FE- SEM), a transmission electron microscope (TEM), such as a cryogenic transmission electron microscope (CRYO-TEM), or an atomic force microscope (AFM). A suitable imaging software may be used to determine the dimensions or the other features. Particle size can be also determined by Dynamic Light Scattering (DLS), spICP-MS, and / or XRD.

[0049] The present disclosure provides a method for activating an electrolysis cell or a CO2 electrolytic device. The electrolysis cell may be for a CO2 electrolytic device, such as designed for a CO2 electrolytic device and / or configured to electrolytically reduce carbon dioxide, or it may be a part of a CO2 electrolytic device. The method may be also a method for regenerating an electrolysis cell or a CO2 electrolytic device, wherein the activation may be carried out to regenerate the electrolysis cell or the electrolytic device. The regenerating may refer to recovering the performance of the electrolysis cell or the electrolytic device. In one embodiment the method is a method for recovering the performance of the electrolysis cell or the electrolytic device. Regeneration is needed when the cell or the electrolytic device is performed for an amount of time and the performance diverts from optimum, i.e. the cell performance depletes, which can be seen as a gradual increase in potential, for example up to 4.0 V. An ideal and / or general rate of depletion is in the range between 10-25 pVh’1, which corresponds to 0.2-0.4 V in 2 years. A regeneration is applied to bring the performance back to the optimum and / or to the initial state. The method may comprise detecting or recognizing an electrolysis cell or electrolytic device in need of activating and / or regenerating, and carrying out the method to activate and / or regenerate the electrolysis cell or the electrolytic device.

[0050] Disclosed is an electrochemical pre-conditioning and / or activating method that activates the electrolysis cell and reduces time required for an electrolyzer or the like electrolytic device to reach optimal and / or desired performance. The method is a simple and effective electrolytic method for activating CO2 cells and / or electrolytic devices to achieve rapid initialization and subsequent stabilized performances. The activation of the cell can be carried out by using a potentiostat, a galvanostat or other suitable controllable power supply. Electrolysis cells and electrolytic devices

[0051] The method comprises providing an electrolysis cell or an electrolytic device, such as a CO2 electrolytic device or any other applicable electrolytic device comprising one or more electrolytic cells, such as comprising one or more gas-fed polymer electrolyte membrane electrolysis cells. The electrolysis cell or the electrolytic device preferably comprises a membrane electrode assembly. The electrolysis cell or the electrolytic device may be newly assembled cells or devices, i.e. unused, or they may be old or used cells or devices, which have been used previously, and which may need regenerating or recovering.

[0052] In one embodiment the method is a method for activating an unused electrolysis cell or an unused electrolytic device before normal operation of the electrolysis cell or the electrolytic device.

[0053] The present devices, which may be defined as electrocatalytic devices, can be used in electrocatalytic methods. Electrocatalysis is a catalytic process involving oxidation and reduction reactions through direct transfer of electrons, which requires electrocatalysts to lower the overpotential of the reactions. The electrocatalytic methods thus require electricity, catalyst and reagents, such as CO2 and H2O.

[0054] Disclosed is an electrolysis cell, such as an electrolytic cell and / or an electrocatalytic cell, or a device, system or a device arrangement comprising such a cell. An electrolysis cell converts electrical energy into chemical energy. The electrolysis cell may be included in a system or an arrangement, for example in a reactor assembly or in an electrolytic device.

[0055] The electrolysis cell comprises an anode and a cathode. The anode and the cathode are arranged in or as a cell, which may be placed or located in a container, which can receive gas and / or liquid, such as electrolyte in the form of gas and / or liquid, usually water vapor or aqueous liquid. The cell may be in a zerogap configuration in a two-compartment cell. In general, the anode operates to complete the redox reaction cycle by oxidation reaction of water resulting in oxygen gas (O2) and carbon dioxide (CO2) formation. The reduction of CO2 occurs on the cathode via a series of proton-electron transfer processes preferably resulting in formation of the specific reaction product distribution. The cell or a cell assembly may comprise a membrane electrode assembly comprising an anode and a cathode, preferably in form of a sheet. The electrodes may be diffusion electrodes. Between the anode and the cathode there may be an ion exchange membrane interposed, which may be a polymer electrolyte membrane (PEM). The polymer electrolyte membrane may refer to any types of suitable membranes, such as anion exchange membranes (AEM), cation exchange membranes (CEM) or bipolar exchange membranes (BPM). Preferably the ion exchange membrane is an anion exchange membrane. Membrane electrode assemblies comprising an anion exchange membrane were found well responsive to the present activation / recovery method. Preferably the membrane is not a proton exchange membrane, as such membranes are used in methods of different field of technology, which are not such responsive to the present method.

[0056] The membrane electrode assembly may be interposed between two fluid flow plates, i.e. flow field plates, having one or more, such as a plurality of channels, for reactant. The channels may be formed in or on the surfaces of the fluid flow plates on the side facing the electrodes, i.e. the channels may be open faced channels. Such a structure may be used in devices such as electrolytic devices and the like.

[0057] The electrolysis cell may have a casing, a frame or a body, including one or more inlets and one or more outlets for liquids and / or gases, and connections for a source of electrical energy, i.e. electric current or electric power. The flow field plates may form the casing, the frame or the body or a part thereof. In most cases the cathode plate is formed of stainless steel and the anode plate is formed of titanium. The anode and the cathode, and / or the flow field plates, are connected or connectable to a source of electric current, such as an external source of electric current, for example a power source or a power supply, which may be controllable. Electric current, such as with desired and / or controlled voltage and / or current, may be applied to the anode and to the cathode, and / or to the flow field plates, to obtain electrochemical, such as electrolytic, reactions in the liquid in contact with the anode and the cathode. The flow field plates may be considered as part of the electrodes, or as the electrodes. The flow field plate may comprise one or more connections for electric energy, more particularly electricity. The connection may comprise one or more connectors for wiring, or apertures or the like receiving portions for the connectors and / or the wiring.

[0058] The flow field plate may comprise an electrically conductive portion. The flow field plate may be used in an electrode, such as in an anode and / or a cathode, in an electrolysis cell, and in an electrolytic device. The flow field plate may be also called as a current collector plate. The flow field plate comprises or is a planar structure, and it typically has two large surfaces, wherein at least one of the large surfaces comprises open faced channels. The flow field plates comprise sides, which have the shortest dimension of the plate and may define the thickness of the plate, such as the highest thickness.

[0059] In applications relating to electrolytic devices and the like devices comprising two or more, such as a plurality, of electrolysis cells arranged as or in a stack, the flow field plates may be arranged in either bipolar and / or monopolar configuration.

[0060] One example provides an electrode comprising a flow field plate comprising an electrically conductive portion, and a gas diffusion cathode, wherein the flow field plate comprises one or more open faced channels, i.e. flow fields, on a surface of the flow field plate. The flow field plate may be configured or designed to receive the gas diffusion cathode. Open faced channels are open to the interior of an electrolysis cell when the flow field plate is installed in the cell. The open-faced channels enable flow and contact of liquid, gas and agents contained in the liquid, i.e. are in fluid and / or gas communication, with an electrode and for example with the catalytic portion of the cell, which may be in a form of a sheet.

[0061] The flow field plate may comprise one or more apertures for inlets and outlets, for example at the sides having the shortest width / thickness. Such apertures may be located on a side of a stack of cells or may be connected to the side of the stack, wherein connectors and / or tubes for incoming and outcoming liquid and / or gases may be connected to the apertures or other receiving parts. In or inside the plates the apertures may be connected to the channels. The one or more channels may be therefore connected from one end to an inlet and from other end to an outlet thus allowing circulation of liquid and / or gas through the electrode or cell.

[0062] The flow field plate may comprise one or more apertures for attaching to the other parts, such as for assembling the cell, for example with one or more screws, bolts, pins or the like attaching means. The parts of the cell may be sandwiched and preferably attached with the attaching means to obtain a cell. The cell may be designed as a single cell or as a stack of cells in bipolar and / or monopolar configuration, wherein the cells are preferably designed to fit each other i.e. they may have compatible sides and / or attaching portions, which allow the cells to be attached to each other. Disclosed is an electrolytic device or device arrangement, such as an electrolyzer, comprising one or more of the electrolysis cells, such as comprising one or more gas-fed polymer electrolyte membrane electrolysis cells, or one or more devices comprising the cell(s), the cell comprising a membrane electrode assembly (MEA). The electrodes may be gas diffusion electrodes (GDE), which comprise a gas diffusion layer (GDL) and a catalyst layer (CL). The membrane electrode assembly comprises an anode GDE and a cathode GDE and a membrane between the anode and the cathode, which assembly is encased between an anode flow field plate and a cathode flow field plate.

[0063] In most cases the electrolysis cells comprises

[0064] -an anode comprising or combined with a flow field plate, i.e. a current collector, and a gas diffusion anode, and / or

[0065] -a cathode comprising or combined with a flow field plate, and a gas diffusion cathode, and

[0066] -an ion exchange membrane between the anode and the cathode. The flow field plate, in the anode and / or in the cathode, may comprise one or more open faced channels on a surface of the flow field plate. The electrodes are in contact with a corresponding flow field plate, such as a cathode 6 is combined with a corresponding cathode flow field plate 1 so that the channels 8 of the cathode flow field plate are in fluid and / or gas communication with the cathode 1 (Fig. 2A). In analogous manner the anode 5 is combined with a corresponding anode flow field plate 2.

[0067] There are several MEA configurations. Preferred configurations include 5-layer systems, where two catalyst layers (one for anode and one for the cathode) are attached to two gas diffusion electrodes (GDEs) and sandwiched between one polymer electrolyte membrane (PEM) resulting in a total of 5 layers. Another configuration includes 3-layer configuration which is essentially the same as the 5 layers but without the two gas diffusion layers (GDLs), and instead the catalyst layers are directly coated on either side of the PEM.

[0068] An electrolytic device in general is a device that uses electricity to split carbon dioxide, water and / or other components into their constituent elements through electrolysis. An electrolytic device as described herein refers to a device setup comprising parts and / or components required to operate the device, including the electrolysis cell(s) and any required other parts and / or components, such as inlets and outlets, and any operating and / or controlling parts and / or components. An electrolytic device may comprise a plurality of electrolysis cells or cell assemblies arranged as a stack, for example wherein the electrolysis cells are flow cells arranged as one or more stack(s). A plurality may refer to two or more, five or more, ten or more, up to hundreds of cells, for example to 2-500, 2-10, 10-500, 10-100 or 10-50. An electrolytic device may comprise the electrolysis cell stack(s), pumps, valves, storage tanks, a power supply, a separator, one or more sensors, and / or other operating components. Electrolysis occurs within the cell stacks when an electric current is applied in the system across the electrolytes. The cells in a stack may be connected to the electric current in parallel and / or in series. Bipolar plates cannot be connected only in parallel. The electrolytic device described herein may be also called as an electrolyzer, or an electrocatalytic device.

[0069] The electrolyzer may be a gas-fed electrolyzer, at least for the cathode side, and it may comprise one or more gas-fed polymer electrolyte membrane electrolysis cells. The anode side may use a liquid anolyte / electrolyte. The gas may comprise CO2, such as humidified CO2 gas, or any other applicable gas, such as inert gas. The electrolyzer may be a CO2 electrolyzer.

[0070] The electrolyzer may be a zero-gap electrolyzer, such as a zero-gap CO2 electrolyzer. Similarly, the electrolysis cell may be a zero-gap electrolysis cell. A zero-gap electrolyzer, or a zero-gap electrolysis cell, has no gap between the cathodes, anodes and the polymer electrolyte membrane (PEM). A zero-gap two- compartment electrolyzer or cell can be specifically used for CO2 conversion to non-liquid products.

[0071] In zero-gap electrolyzers both catalyst layers in the cathode and anode GDEs are in direct contact on either side of the membrane. Zero-gap electrolyzer typically constitute in a 2-compartment electrolyzer.

[0072] The present cathode enables implementing the electrolytic device in the form of any applicable electrolytic device with any applicable structure. For example, the electrolytic device may be a two-compartment electrolytic device or a three- compartment electrolytic device. A two-compartment electrolytic device may be used for acids or acidic conditions. A three-compartment electrolytic device may be used to maximize liquid product output, such as liquid hydrocarbon output. The electrolytic device may be a CO2 electrolytic device. The present disclosure provides an electrolysis cell, which may be an electrolytic device cell or a cell for an electrolytic device, the electrolysis cell comprising -an anode, -a cathode, and

[0073] -preferably an ion exchange membrane between the anode and the cathode, wherein

[0074] -the cathode is the cathode disclosed herein. Preferably the anode and the cathode are connected or connectable to a source of electric current, such as to a power supply for providing electric current to the electrolysis cells.

[0075] The electrolysis cell may be a flow cell. In a flow cell a flow of stream is arranged into the cell, such as a flow of liquid and / or a flow of gas. The flow may be continuous, in which case the cell is a continuous flow cell.

[0076] Disclosed is an electrolytic device for reducing carbon dioxide to products, such as hydrocarbons, alcohols, carboxylic acids and / or to CO, the electrolytic device comprising one or more, such as a plurality of, for example two or more, the (activated) electrolysis cells disclosed herein, preferably arranged as a stack. The device may comprise

[0077] -an inlet for reactant stream and / or feed, such as a source of carbon dioxide, and -an outlet for reaction products, such as a stream and / or feed thereof.

[0078] The electrolytic device may be a continuous electrolytic device, which may be used for continuous electrolysis of carbon dioxide, preferably humidified carbon dioxide.

[0079] Preferably the device comprises two or more of the activated electrolysis cells. In such case the electrolysis cells may be flow cells arranged as one or more stack(s).

[0080] In one example the electrolytic device comprises

[0081] -one or more, such as a plurality, for example two or more, of the (activated) electrolysis cells disclosed herein, preferably arranged as a stack, and

[0082] -a power source and / or a power supply and / or wherein the electrolytic device is connectable to a power source and / or a power supply. The power supply or the power source is arranged to provide electric current to the anode and the cathode, or to the electrolysis cell(s). The electrolytic device may comprise connectors and / or wiring for the power source or the power supply. The power supply may refer to a device controlling the application of power and / or properties thereof, which usually converts electric current from a source to the correct voltage, current, and frequency to power the load. Power supply may be referred to as an electric power converter. The power supply may be controllable, for example by controlling means such as a control unit, to which it may be operatively connected, so that desired voltage or current may be obtained and provided to the anode and the cathode. The power timing, pulsing, frequency, polarity, and / or the like parameters may be also controlled. In one example the power supply comprises or is a potentiostat or a galvanostat, which may be used for controlling the activating method. The present activation treatment (’’reverse operation”) requires switching of polarity that is not trivial to common DC power sources. The power supply may be a software-controlled DC power supply with a polarity-reversing switch or other suitable polarity-reversing means.

[0083] The electrolytic device, the electrolytic device system or the reactor assembly, which may be called as device, system and / or assembly, or a combination thereof, may comprise, be connected or be connectable to a power source or power supply. Any operating components may be operatively connected to controlling means, which enable the controlling means to control such as operate, the component(s). The electrolytic device, the electrolytic device system or the reactor assembly may be electronically controllable, thus comprising one or more controlling means, such as electronic control means, for controlling the operation of the electrolytic device. The controlling means may be or comprise one or more electronic control units, which may be programmable, comprising one or more processors, memory, and software configured, when executed with a processor in the control unit, to carry out one or more operations to implement the method. The control unit may be, comprise and / or be connected to a computer. The controlling means may be for example arranged to operate a power source or a power supply, for example to adjust the voltage, current, frequency, switching on and off and the like, and / or to adjust temperature, pressure and / or flow of liquids and / or gases by controlling and / or adjusting any of the operating components of the device, the system or the assembly, such as one or more pumps, valves, source of pressurized gas, actuators and / or the like, which may be operatively connected to the controlling means. The controlling means may be arranged to maintain one or more of said parameters in a desired range. The controlling means may be arranged, such as programmed, to monitor one or more properties from the device, the system, and / or the assembly, for example as a function of time, and as feedback to the monitored properties carry out one or more control actions in the device or the system to adjust the function of the device to carry out the present method and / or to maintain a property at a desired range and / or to a desired value.

[0084] The electrolytic device may comprise flow control means, which may also be or comprise pressure control means, arranged to control flow and / or pressure in the electrolytic device and / or in the electrolysis cells. The flow control means may be operatively connected to controlling means. The flow control means may include one or more sensors for detecting flow and / or pressure in a cell or the electrolytic device / reactor, such as gaseous flow and / or pressure and / or liquid flow and / or pressure, which sensors may be connected to controlling means. The controlling means may be arranged, as feedback to the detected pressure, to control one or more devices and / or parameters to adjust the pressure in a desired range. For example, the electrolytic device may comprise one or more means for adjusting the pressure, such as one or more pumps, valves, sources of pressure, actuators, and / or the like, which may be operatively connected to the controlling means.

[0085] The portion of an electrolyte near the cathode, especially in a cell in which the cathode and anode are in separate compartments, may be called catholyte. Correspondingly the portion of an electrolyte near the anode, especially in a cell in which the cathode and anode are in separate compartments, may be called anolyte.

[0086] In one example the electrolytic device comprises one or more electronic control means for controlling the operation of the electrolyzer, such as pressure control means arranged to control the pressure in the electrolytic device and / or in the electrolysis cells.

[0087] Activation

[0088] The present electrolysis cells and the electrolytic devices can be activated with a activation method to enhance the operation thereof and / or to recover the performance of an electrolysis cell and / or an electrolytic device, which may have been operated for a certain period of time and wherein the performance thereof may have been decreased. The method may comprise detecting and / or identifying such a decreased performance and / or other need for activation and / or regeneration, and when detected and / or identified, carrying out the preconditioning and / or activation method. What is discussed herein for activation also applies to regeneration, i.e. the activation may be carried out to regenerate the cell.

[0089] The present method for activating an electrolysis cell or an electrolytic device comprises providing a controllable power source, such as a potentiostat, connected to the electrolysis cell(s) to activate the electrolytic cell. An example of the device setup is presented in Figure 14C, wherein the setup can be controlled by a computer. A potentiostat is a control and measuring device comprising an electric circuit, which controls the potential across the cell by sensing changes in its resistance, varying accordingly the current supplied to the system. A higher resistance will result in a decreased current, while a lower resistance will result in an increased current, in order to keep the voltage constant as described by Ohm's law.

[0090] A galvanostat is a control and measuring device comprising an electric circuit, which is capable of keeping the current through an electrolytic cell in coulometric titrations constant, disregarding changes in the load itself.

[0091] The activation method preferably comprises flowing anolyte and catholyte through the electrolysis cell(s), such as for at least 5 or 10 minutes, prior to activation. A time period of 10-30 minutes was found suitable for most cases. This preactivation or precirculation step can provide stable conditions for the actual activation. Shorter flowing times can also work especially for more porous electrodes (diffusion). The activation method itself can assist or encourage diffusion through the GDEs.

[0092] The methods disclosed herein preferably do not comprise, and / or are carried out in the absence of, gaseous streams and / or flows other than CO2 or other reactant gas, or gaseous streams and / or flows such as gases and / or vapours of one or more of recovery gas other than the reactant gas, isopropanol, ethanol, ammonia, N2, O2, N2H2, HCI, sulphur dioxide and / or nitrous oxide, and / or in the absence of activating agents, such as alkali or alkali earth metal cations, or in the absence of acidic conditions, such as in conditions close to neutral pH, such as at a pH of 6 or higher, such as in a range of 6-10, such as 6-8.. The pH may refer to the pH of the liquid comprising the carbon dioxide and / or to catholyte, and / or other liquid provided to the electrolysis cell and / or in the electrolysis cell. The activation may not require flow conditions, but some electrolyte (moisture / H2O) needs to be present. Flow conditions are required to maintain target current under normal cell operation. The activation treatment may work for gas fed water electrolyzer, where CO2 is replaced with an inert gas, such as noble gas or nitrogen.

[0093] The methods disclosed herein are preferably also carried out in the absence of prior art methods and / or reagents not described herein for the present method, such as in the absence of electrochemical potentiostatic and / or galvanostatic polarization, overpotentials, short-circuiting, and / or cyclic voltammograms / voltammetries (CVs) as well as external methods such as elevating temperature or pressure and the use of activating reagents or recovery gas.

[0094] The activation comprises operating the power supply while monitoring the current density. An open circuit potential may be measured, such as until a stable result is obtained, for example for 60 seconds. The method may further comprise applying initial positive linear sweep voltammetry (LSV), preferably from open circuit potential, such as from the measured open circuit potential, preferably to obtain an increase in current density. The linear sweep voltammetry may be linear sweep voltammetry with a reverse potential. The open circuit potential (OCP) is the potential of the cell when there is no current flowing through. The initial positive linear sweep voltammetry is a first linear sweep voltammetry. The initial positive linear sweep voltammetry may be applied / provided to a voltage from the open circuit potential to an upper limit in the range of 3.3-4.0 V, such as 3.3-3.8 V. In one example the initial positive linear sweep voltammetry is applied / provided to a voltage from the open circuit potential to an upper limit of about 3.4 V. The activation, such as the initial positive linear sweep voltammetry, may be ended when the target voltage is obtained and / or when the increase in current density is obtained. The initial LSV may serve as a control. However, as a control another method may be used instead, such as one of the methods discussed in the following.

[0095] It was found out that the electrolysis cell or the electrolytic device comprising the electrolysis cell can be efficiently activated with a suitable method applying a (small) reverse current to the cell and / or by reversing the electrochemical polarity applied to the cell. This can be controlled by potential or by current. The reverse current is reverse to the current of the normal operation of the cell, i.e. to operational current, which comprises any suitable electrolytic method for obtaining one or more reaction products from the reactant. In the case of the reverse current, the flow of electrons is reversed so that the electrode that serves as a cathode during normal operation serves as an anode during application of reverse current, and the electrode that serves as an anode during normal operation serves as the cathode during application of reverse current.

[0096] The method comprises applying an activating reverse current treatment to the electrolysis cell, which reverse current is reverse to the current of the normal operation of the cell, and / or applying an activating reverse potential treatment to the electrolysis cell, which reverse potential is reverse to the potential of the normal operation of the cell.

[0097] The present method does not require and involve prior art activation steps, such as use of recovery gas, which has a different composition to reactant gas, and / or creating an electrical short circuit between the anode and cathode, or other prior art methods or steps discussed herein.

[0098] The method may comprise applying one or more activating reverse current treatments, which is reverse to the current used in the normal operation of the electrolysis cell or the electrolytic device, to the electrolysis cell, preferably to obtain an onset in current density. The activating reverse current treatment is applied subsequently to the initial positive linear sweep voltammetry, if carried out. The activating reverse current treatment may be a sweep or a step. A sweep refers to a gradual change of current from an initial value to a final value over a time period, for example with a sweep rate disclosed herein, and a step refers to an immediate change of current from initial value to a final value. The present activation method may comprise applying one or more activating reverse current treatments. The present activating treatment may be the only activating treatment carried out in the method.

[0099] The method may comprise applying one or more activating reverse potential treatments, which is reverse to the potential used in the normal operation of the electrolysis cell or the electrolytic device, to the electrolysis cell, preferably to obtain an onset in potential. The activating reverse potential treatment is applied subsequently to the initial positive linear sweep voltammetry, if carried out. The activating reverse potential treatment may be a sweep or a step. A sweep refers to a gradual change of potential from an initial value to a final value, i.e. range, over a time period, for example with a sweep rate disclosed herein, and a step refers to an immediate change of voltage, current and / or potential from initial value to a final value, i.e. range. The present activation method may comprise applying one or more activating reverse potential treatments. The present activating treatment may be the only activating treatment carried out in the method.

[0100] If the current is reversed, a change in potential is measured by varying the current density range. If the potential is reversed, a change in current density is measured by varying the potential range.

[0101] The activating reverse current treatment and / or the activating reverse potential treatment may be applied to obtain an onset in current density, such as until a target current density, especially target current density for activation, of 150 mAcnrr2or more, preferably at an operational cell potential, such as at a typical operational cell potential, is obtained. The (typical) operational cell potential may be presented as a range and / or comprising one or more of the potential values or ranges thereof disclosed herein. For example, for the initial positive linear sweep voltammetry the operational cell potential may be from OCP to 3.4 V. For the activating reverse potential treatment, the operational cell potential may be from -3 to +4 V, preferably from -2 to 3.4 V.

[0102] The target current density may be up to 700 mAcm-2, such as up to 600 mAcirr2or up to 500 mAcirr2. However, it may be desired to use a lower upper target current density to protect the cell, such as 400 mAcirr2or less, 300 mAcirr2or less, 250 mAcirr2or less, or preferably 230 mAcirr2or less, such as 220 mAcirr2or less. The target current density, especially target current density for activation, may be for example 170 mAcirr2or more, 180 mAcirr2or more or 190 mAcirr2or more, for example in the range of 170-700 mAcirr2, such as in the range of 180-220 mAcirr2or any other combination of ranges of lower and upper values. This may be considered as a current density cut-off value or range.

[0103] The activating reverse current treatment and / or the activating reverse potential treatment may comprise voltammetry and / or a potential or current step or sweep. In embodiments the method comprises applying one of a linear sweep voltammetry, a staircase voltammetry and a potential or current step. With these methods it was possible to obtain an activated cell, which exhibits a stable potential, which can be detected by the performance test described herein. In one embodiment the activating reverse current treatment comprises applying a reverse current sweep or step in the range from -200 mA cm-2to 240 mA cm-2, such as for 5-1000 s.

[0104] In one embodiment the activating reverse potential treatment comprises applying a reverse potential, such as a reverse potential sweep or a step, in the range of 5- 100 mAcm-2, such as for 5-1000 s, such as 5-60 mAcm-2or 20-60 mAcirr2and / or for 5-500 s, or 5-300 s.

[0105] In one embodiment the method comprises applying a (second) linear sweep voltammetry to obtain an onset in current density, preferably at about 2.3 V, until a target current density, especially target current density for activation, of 150 mAcm-2or more at an operational cell potential is obtained.

[0106] In normal present LSV activation (50 mV / s) the amount of transferred negative charge is about 500 mC / cirr2(based on Fig. 1). The same negative charge, Q, can be transferred by applying a negative current of 50 mAcm-2for 10 s (Q = It).

[0107] The current density cut-off ensures that current density does not exceed the desired limit (the target current density) and cause damage to the MEA. When current density exceeds the limit, the LSV may be (automatically) ended and the method may proceed to the next step.

[0108] The activating reverse current treatment and / or the activating reverse potential treatment, such as the sweep, may be applied / provided from about -2 to -1 V, such as from about -2 V, to about 2.9-4.0 V, or to about 3.0-4.0 V, such as to about 3.3-3.8 V. In one embodiment the method comprises applying the activating reverse potential treatment from -2—1 V to +2.9-4.0 V. In one embodiment the activating reverse current treatment and / or the activating reverse potential treatment is applied / provided from about -2 V to about +3.4 V, which is suitable for all the present activating methods.

[0109] In one embodiment the method comprises applying the initial positive linear sweep voltammetry (LSV), and / or applying the activating reverse potential treatment, with a sweep rate in the range of 40-100 mVs’1, such as in the range of 40-70 mVs’1, for example in the range of 40-60 mVs’1, or about 50 mVs’1. The sweep rate, i.e. how quickly the LSV’s are performed, is an important parameter, as it was experimentally confirmed that the activation does not perform as well with lower sweep rates.

[0110] The activating treatment may be carried out for a time period enabling the activation, which may be 5 minutes or less, such as 1-20 minutes, 1-15 minutes, or 2-10 minutes, for example. The required time is not dependent on the size of the cell.

[0111] In one embodiment the method comprises carrying out a performance test, such as monitoring stability of the cell, for example by applying a galvanostatic measurement, at the target current density, and / or by applying a constant / fixed current density. The electrolysis cell is supplied with a current from the power supply, such as about 1 A for 5 cm2electrolysis cell or about 50 A for a 250 cm2electrolysis cell., to obtain a current density that may be any target current density disclosed herein, especially target current density for activation, such as a current density of about 200 mAcm-2, until the electrolysis cell performs at a stable potential, such as of about 2.9 V, about 3 V or about 3.0 V, about 3.1 V or about 3.2 V or another value as disclosed in the examples and / or a stable value in the range of 3.0-3.6 V, such as 3.0-3.3 V, for at least 100 minutes, such as for at least 200 minutes as shown in Figures 2 and 9, determined by electrochemical voltage vs. time (chronopotentiometry) measurements. Even lower limits may be applied, such as in the tests even a current onset at 2.3 V was used at room temperature. Further experimental data supports long term stabilities of even 500 to 2000 hours.

[0112] This indicates / identifies an activated electrolysis cell. The stability may be also monitored by electrochemical impedance spectroscopy (EIS) Nyquist plots at the target current density. The stable potential refers to maintaining the same or substantially the same voltage value, such as within a tolerance or variation of 2 % or less, 1 % or less, or 0.5 % or less, during the time period. For example, from Figure 6, which is obtained from activation method C, it can be seen that the potential is not stable but increases constantly. The stable potential indicates and identifies that the cell is activated with the present method and / or that the cell passes quality control. The performance test may be carried to evaluate the quality of the activated cell, and / or to confirm that the activation was successful.

[0113] Figure 13 shows a flow diagram of an example of the activation method, which is suitable for a CO2 electrolyzer comprising one or more electrolysis cells. The process starts with pre-circulation (flowing) of anolyte and catholyte through the cell in step 30. After the pre-circulation has been carried out for a suitable time, such as for 10-30 minutes, an open circuit potential (OCP) is measured from the cell for 60 seconds in step 32. Next, a linear sweep voltammetry (LSV) is applied from OCP in step 34, such as to 3.4 V at 50 mVs’1. Voltage vs current density response is recorded with a cut-off current density at > 200 mAcirr2. Next an activating reverse potential treatment, such as a linear sweep voltammetry (LSV), is applied in step 36, such as from -2 to 3.4 V at 50 mVs’1for 110 seconds. The steps 12-16 represent an example of the activation method A. Subsequently in step 38 a performance test is started at a constant current, such as 200 mAcirr2, and potential time vs time response is measured.

[0114] In one example the method for activating an electrolysis cell or a CO2 electrolytic device comprises

[0115] -providing an electrolysis cell or a CO2 electrolytic device comprising one or more electrolytic cells comprising a membrane electrode assembly,

[0116] -providing a potentiostat connected to the electrolysis cell(s) to activate the electrolytic cell,

[0117] -flowing anolyte and catholyte through the electrolysis cell(s), for example for 10- 30 minutes prior to activation,

[0118] -operating the power supply while monitoring the current density,

[0119] -measuring open circuit potential of the electrolysis cell(s),

[0120] -preferably applying initial positive linear sweep voltammetry (LSV) from the measured open circuit potential to a voltage in the range of 3.3-4.0 V with a sweep rate in the range of 40-100 mVs’1to obtain an increase in current density, and

[0121] -applying a second linear sweep voltammetry with a reverse potential from -2—1 V to 2.9-4.0 V with a sweep rate in the range of 40-100 mVs’1to obtain an onset in current density, until a target current density of 170 mAcm-2or more is obtained, and ending the second linear sweep voltammetry.

[0122] The present disclosure provides an activated electrolysis cell for reducing carbon dioxide to products, the electrolysis cell comprising a membrane electrode assembly comprising -an anode, -a cathode, and

[0123] -an ion exchange membrane between the anode and the cathode, wherein the electrolysis cell has been activated with the present method. The activated electrolysis cell can be identified by detecting one or more of the characteristic features disclosed herein. A non-activated electrolysis cell or an electrolysis cell activated with a different method exhibits different features, as shown in the examples.

[0124] In one embodiment the activated electrolysis cell performs at a stable potential of about 3 V for at least 100 minutes, such as for at least 200 minutes, for at least 100 hours, for at least 500 hours, for at least 1000 hours or even for at least 2000 hours, determined by electrochemical voltage vs. time (chronopotentiometry) measurements.

[0125] The present disclosure provides an activated CO2 electrolytic device for reducing carbon dioxide to products, such as to hydrocarbons, alcohols, carboxylic acids and / or to CO, the electrolytic device comprising

[0126] -one or more activated electrolysis cells disclosed herein, and

[0127] -a power supply for providing electric current to the electrolysis cells.

[0128] In one embodiment the CO2 electrolytic device performs at a stable potential, such as of about 3 V, for at least 100 minutes, such as for at least 200 minutes, for at least 100 hours, for at least 500 hours, for at least 1000 hours or even for at least 2000 hours, determined by electrochemical voltage vs. time (chronopotentiometry) measurements.

[0129] After the electrolysis cell or the electrolytic device has been activated, it can be used for the normal operation of the electrolysis cell or the electrolytic device, and / or the normal operation may be resumed.

[0130] In one embodiment the activated electrolysis cell is an unused electrolysis cell.

[0131] In one embodiment the activated electrolysis cell is a recovered electrolysis cell.

[0132] Electrodes

[0133] The cathode and optionally also the anode may comprise a catalyst layer on a support. The cathode may comprise a catalyst layer on a cathode support and the anode may comprise a catalyst layer on an anode support, such as a thin layer of catalyst material disposed on their major surfaces at the interface with the interposed membrane. The catalyst may be different in the cathode and in the anode. It was found out how to obtain suitable catalyst in the cathode to promote desired electrolytic reactions. The present cathode can be used with any suitable anode and in any suitable device, device arrangement and / or process.

[0134] The anode comprises anode support, which may comprise or be same material as the cathode support, or it may comprise or be different material. The support in general may be called an electrode support. The anode may or may not contain a catalyst on the anode support. If the anode comprises a catalyst, the catalyst may be different from the catalyst on the cathode support. The anode may be prepared by using the same or similar methods, however preferably from different materials.

[0135] In one example the cathode support and / or the anode support comprise porous material, preferably porous electrically conductive material, which may be in a sheet or a layer form, and which may have planar major surfaces, such as carbon fibre paper or sheet. The cathode support is preferably a cathode support layer and / or the anode support is preferably an anode support layer. A gas diffusion electrode can be obtained by using such a porous electrode support.

[0136] The cathode support and / or the anode support may be a gas diffusion layer (GDL), and the support may comprise two layers: a macrofibrous layer (a backing layer) and a microporous layer (MPL). The catalyst layer (CL) is applied and / or adhered to or is on the microporous layer.

[0137] The present electrode may be a gas diffusion electrode. A gas diffusion electrode (GDE) comprises a gas diffusion layer (GDL) and a catalyst layer (CL). The anode may be an anode comprising an anode catalyst layer deposited on a gas diffusion layer (an anode GDE). The cathode may be a cathode comprising a cathode catalyst layer deposited on a gas diffusion layer (a cathode GDE). These kinds of electrodes were found to respond well to the present activation method.

[0138] The anode may be based, or comprise, one or more suitable compounds, such as metal, metal oxides, mixed metal and / or mixed metal oxides of Ir, Ru, Rh, Pt, Ni, Fe, such as iridium, lrO2, or NiFe, transition metals, and the like materials. Commercially available anode materials may be used in the present devices and methods. Disclosed is a metal catalyst and a metal alloy catalyst, i.e. a mixture of metals, which metal catalyst or metal alloy catalyst may be used in electrolytic applications. The metal catalyst or the metal alloy catalyst may comprise or be in a form of nanoparticles. The metal catalyst or the metal alloy catalyst may be obtained with the methods disclosed herein.

[0139] Disclosed is a cathode for an electrolysis cell, the cathode comprising metal alloy catalyst in the form of nanoparticles on a cathode support. The cathode is especially suitable for a CO2 electrolytic device.

[0140] In one embodiment the cathode comprises a metal and / or metal alloy catalyst, which may be on, or which may be deposited on, a cathode support. A catalyst may comprise one or more transition metal and / or alloy thereof. A catalyst may comprise one or more elements selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, Sn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Ir, Pt, Au, Hg, Al, Si, In, Tl, Pb, Bi, Sb, Te, U, Sm, Tb, La, Ce, and Nd. It was found advantageous to use copper in the catalyst, preferably in combination with silver. Especially catalysts in the form of nanoparticles were found advantageous for the present methods. Other suitable catalytic materials include zinc, nickel, aluminium, titanium and cobalt, or transition metals in general.

[0141] In one embodiment the catalyst comprises Ag and Cu, preferably the catalyst is a metal alloy catalyst consisting of Ag and Cu. In such as the catalyst layer preferably does not contain other catalysts. It was found out that the combination of Ag and Cu enabled promoting the reactions towards formation of specific hydrocarbons, such as ethene. The selectivity of the reaction could be enhanced by providing the alloy in the form of nanoparticles. The selectivity may be 80% or more, such as 90% or more, even 95% or more. Selectivity data may be obtained using gas-chromatography whereby the products are analysed with respect to known calibration standard gases. More specifically, the peak areas for each chromatographic peak (product) are compared with known calibration standards. These raw product values (%) can then be converted into other more meaningful data including overall product selectivity (%), Faradaic efficiency (FE, %) and energy efficiency (%). The high selectivity is of practical value only when the activity of the reaction in terms of the turn-over-frequency is sufficiently high, which was achieved with the present catalysts. This is the main concern with the electrocatalytic reduction of CO2 to feedstock chemicals. The selectivity and the stability can be controlled by either tailoring the AgCu alloy ratios as demonstrated in the examples, and / or by altering the ionomer mixture.

[0142] It was also found out that the catalysts comprising Ag and / or Cu responded especially effectively to the present activation and regeneration method.

[0143] Preferably the catalyst comprises AgCu alloy, such as AgCu alloy nanoparticles. For the thermodynamically stable performance under electrochemical conditions, the AgCu composition of the nanoparticles may vary as follows: Ag(99-90 wt%)Cu(1-10 wt%), Ag(1-10 wt%)Cu(99-90 wt%) or Ag(1-5 wt%)Cu(99-95 wt%). In one example the Ag:Cu ratio is in the range of 1-10:99-90 (wt%), which was found to provide improved electrocatalytic performance, including stability and selectivity, especially in combination with ionomers and / or binders.

[0144] In one example the metal alloy catalyst comprises phase-separated Ag / Cu alloy nanoparticles. Especially phase-separated AgCu alloy nanoparticles were experimentally confirmed to provide desired selectivity. These alloys could enhance the selectivity of the reactions towards formation of ethene. The selectivity was higher than the selectivity of corresponding metal catalyst comprising only Ag or Cu. For example, it was possible to convert 90 % or more, such as 95 % or more, of all the formed hydrocarbons into ethene.

[0145] The formation of phase separated nanoparticles is a direct result of the synthetic method(s) described herein, such as depositing methods, for example a method comprising electrodeposition. The phase-separation refers to structural change of the nanoparticles and exact metastructure thereof, which can be controlled and tuned by selecting the appropriate reaction conditions, such as temperature, concentration, current, and time.

[0146] X-ray photoelectron spectroscopy (XPS) and / or transmission electron microscopy with energy dispersive spectroscopy analysis (TEM-EDS) data can be used to confirm the phase-separated structure and to distinguish from non-phase- separated structure.

[0147] The present catalysts are preferably obtained with the method disclosed herein, wherein the metal alloy nanoparticles are formed either directly on the cathode support or deposited from a nanoparticle catalyst containing ink solution or dispersion, or a combination of both. By “combination of both” it is meant that it is possible to deposit a first set of nanoparticles, such as by ink deposition, to obtain a first deposit, and subsequent deposit a second deposit, such as by depositing a second set of nanoparticles by electrodeposition on top of the first deposit. It was found out that nanoparticles formed on the cathode support were better suitable for cathodes for electrolysis cells and for devices comprising the cells, compared for example with preformed nanoparticles which would be combined with cathode support.

[0148] The nanoparticles may have an average particle diameter, such as number average particle diameter, in the range of 10-50 nm, such as 15-25 nm or 20-40 nm, determined microscopically. The average nanoparticle size can also be estimated by X-ray diffraction (XRD). The average crystallite size (D) can be estimated according to the Scherrer equation which correlates peak broadening to the average crystallite size:

[0149] D = kA / pcosO, where 3 is the full width at half maximum (FWHM) of the diffraction peak after instrumental broadening correction and k is the shape factor for the average crystallite. 3 is calculated from 02 = 0o2 - b2, where 0o is the measured FWHM of the sample and b is the measured FWHM of a well crystallized material (LaB6, 99.5%) to account for instrument broadening and k = 0.9 for powders, assuming spherical shape.

[0150] Nanoparticles can be characterized with suitable methods. XRD constitutes a primary method of characterization on nanoparticles and nanoparticle alloys synthesized and applied as electrocatalysts in the present electrolytic devices. Other characterization methods include electron microscopy ( / .e. TEM), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). XRD analysis is used to confirm crystal data including, phase composition, crystal structure and size of the synthesized nanoparticles. In addition, XRD can be used to detect the presence of inorganic impurities. Individual XRD pattens of for example individual Cu or Ag nanoparticles, as well as AgCu nanoparticle alloys could be identified and used for characterizing the nanoparticles.

[0151] The catalyst or the cathodes comprising thereof can be prepared by using two different approaches. The first comprises deposition, such as electrodeposition, of ions directly onto the surface of a gas diffusion layer or other porous layer, such as a carbon fibre paper. The second approach requires two steps comprising first pre-synthesizing the nanoparticles or nanoparticle alloys and then forming a dispersion with the synthesized nanoparticles, and any ionomer / binder, carbon powder and / or appropriate solvent, that is deposited onto the gas diffusion layer or the other porous layer by airbrushing and / or spray coating and / or dried i.e. annealed and / or post-annealed. In one example the synthesis of the nanoparticles comprises providing individual Cu or Ag nanoparticles, preferably having a number average particle diameter disclosed herein, for example 20-100 nm, then introducing an alloying ion (Ag+, Cu+or Cu2+) and / or one or more oxides thereof in a suitable medium, such as water or an aqueous solution or mixture, and applying a reducing agent, such as ethene glycol or hydrogen, and / or reducing conditions, such as at elevated temperature, for example at 60 °C or more, and / or at elevated pressure, to obtain the desired nanoparticle alloy. The ratio between the starting nanoparticle and the alloying ion determines the properties of the final nanoparticle alloy.

[0152] The depositing methods disclosed herein may comprise controlling reaction conditions, such as temperature, concentration, current, and time, to obtain desired properties of the catalyst material, such as nanoparticles, for example desired metastructure, for example phase-separated structure.

[0153] The carbon powder may comprise any suitable carbon powder, such as comprising carbon particles, for electrodes, such as carbon black, conductive carbon and / or the like, which can be used as a (catalyst) support and / or conductive material in the electrodes, such as in anodes and / or cathodes. One example of commercial carbon powder is Vulcan XC-72. The carbon powder may have an average (basic) particle size in nanometre range, such as in the range of 20-100 nm, such as 20-50 nm or 30-60 nm.

[0154] In one example the catalyst is obtained by

[0155] -providing a support,

[0156] -providing a solution comprising Ag+and / or Cu+and / or Cu2+, and / or a dispersion comprising Ag, Cu and / or AgCu alloy nanoparticles and optionally binders, and -electrodepositing, airbrushing and / or (ultrasonic) spray coating the solution and / or the dispersion to the support to form a catalyst layer on the support, preferably the catalyst comprising metal alloy nanoparticles, such as a catalyst layer comprising Ag, Cu and / or AgCu alloy nanoparticles. A method for preparing a cathode may comprise -providing a cathode support, which may be pretreated, -providing a solution comprising Ag+and / or Cu+and / or Cu2+, and / or providing a dispersion comprising Ag, Cu and / or AgCu alloy nanoparticles, and -electrodepositing, airbrushing and / or (ultrasonic) spray coating the solution and / or the dispersion to the cathode support to form a catalyst layer on the cathode support, preferably the catalyst comprising metal alloy nanoparticles, such as to form a catalyst layer comprising Ag, Cu and / or AgCu alloy nanoparticles, to obtain the cathode. The cathode may be the cathode disclosed herein.

[0157] In one example the method for preparing a cathode comprises -providing a cathode support, -providing a solution comprising metal ions, such as a solution comprising Ag+and / or Cu+and / or Cu2+, and -electrodepositing the solution to the cathode support to form metal alloy nanoparticles, such as to form a catalyst layer comprising the metal alloy nanoparticles on the cathode support.

[0158] The electrodeposition may be carried out by any suitable electrodeposition method. In one example electrodeposition comprises providing a gas diffusion layer or other porous layer, such as a carbon fibre paper or sheet, such as pretreated carbon fibre paper or sheet. The porous layer may comprise a macrofibrous layer and / or a microporous layer. The porous layer may be pretreated with concentrated nitric acid (HNO3). More particularly, to prepare a substrate or a gas diffusion layer for electrodeposition a pre-treatment may be carried out to increase the hydrophilicity of the substrate, as typically the gas diffusion layer, such as a carbon paper, may contain PTFE (Teflon) coatings, such as 5 wt% or more, that are on the surface and make the carbon paper hydrophobic. Though the hydrophobicity is needed for gas diffusion properties of the GDL it can provide adverse effects when placed in aqueous electrodeposition / plating baths and can lead to poor deposition. To improve this some of the PTFE can be stripped off by using the nitric acid on the surface for short periods time, such as for 1-24 h. In case the substrate does not contain PTFE, the pre-treatment is not required.

[0159] The porous layer may be fixed to a substrate or holder, such as a glass substrate. This is to ensure that electrodeposition only occurs on the microporous layer and not on the macrofibrous backing. The substrate including the porous layer may be immersed into an electroplating solution comprising a mixture of metal ions comprising Cu2+or Cu+and Ag+. The pH of the solution may be adjusted by using acid, such as HCI or H2SO4. Additives such as complexing agents may also be used. These can be used to tune the morphology of the nanoparticles. The (micro)porous layer is subjected to electrodeposition, for example by using a two- electrode configuration comprising the porous layer as the working electrode and a counter electrode, such as a copper-based counter electrode. A current density of -15-25 mAcm-2may be applied, such as at a constant mode or at a pulsed deposition mode, until the desired thickness / charge density is obtained. The resulting films may be washed, such as with deionized water, and annealed at an elevated temperature, such as at a temperature between 100-150 °C, for 30-120 minutes, such as for about 1 h.

[0160] The dispersion, which may be a solution, may comprise metal ions dispersed and / or soluble in a suitable liquid, such as aqueous liquid or organic solvent, for example water, or a suitable mixture of water and organic solvent, such as water and isopropanol. The dispersion may also comprise already formed and / or obtained nanoparticles, wherein the dispersion may be called as ink, and which may be used in methods such as airbrushing and ultrasonic spray coating system. The obtained nanoparticles comprise or consist of the metal catalyst and / or the metal catalyst consists of the nanoparticles. The dispersion may or may not comprise an ionomer. If an ionomer is used, it can be added also at a different point, such as to a cathode support without a catalyst, and / or to a formed catalyst on the support.

[0161] The porous layer may comprise an ionomer and / or binder coating, or it may be uncoated. Ionomers and / or binders may be added to the dispersion(s) to improve consistency and / or mechanical stability. They also improve electrical / ionic conductivity of catalyst layer as well as adherence to a gas diffusion layer or other porous layer, such as a carbon paper. Ionomers may also behave as co-catalysts for tuning CO2RR selectivity. Key difference between ionomer and binder is that ionomers facilitate ion transport whilst binders do not. Binders instead mostly act as a ‘glue’ to ensure that nanoparticles / active material is secured to the substrate. The binder may be ionomeric or non-ionomeric. The binder may be a polymeric binder, such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride. In the case of PTFE it also provides chemical and temperature stability. The catalyst may further comprise one or more ionomers, which can modify the selectivity of the catalysed electrochemical carbon dioxide reduction. The ionomer may be anionic or cationic, or a mixture thereof. Charge and hydrophobicity / hydrophilicity are important parameters of the ionomers. The ionomer provides effects related to charge transfer between the catalyst and the ionomer, which can for example weaken adsorption energy of a reaction product.

[0162] Examples of ionomers comprise imidazolium functionalized polystyrene, for example available as a commercial product Sustainion, or sulfonated polytetrafluoroethene, for example available as a commercial product Nation or Teflon.

[0163] The airbrushing may be carried out by any suitable airbrushing method and / or equipment. Airbrushing is preferably used only in the case of preformed nanoparticles, but not in the case of electrodeposition. For small scale cells, such as having an electrode area of 250 cm2or less, an airbrush pen may be preferred whilst for larger scale, such as more than 250 cm2, an automated ultrasonic spray coating system may be preferred. Both methods use a carrier gas which can be air or an inert gas such as N2. The support, such as substrate, gas diffusion electrode or carbon paper, in which the deposition is applied to, may be heated at elevated temperature.

[0164] Alternatively, nanoparticles can be applied by using ultrasonic spray coating method, and also preferably only in the case of preformed nanoparticles. The ultrasonic spray coating may be carried out by using any suitable ultrasonic spray coating method and / or equipment. Both the airbrushing and the ultrasonic spray coating can be easily scaled up to coat large surface areas. The cathode support may be as discussed in previous, for example it may be pretreated, such as a pretreated carbon fiber paper.

[0165] In airbrushing or ultrasonic spray coating nanoparticles may be provided as a nanoparticle ink dispersion, which may be the dispersion disclosed herein. The nanoparticle ink dispersion may comprise 20-300 gL’1of the nanoparticles, such as 50-200 gL-1. The cathode may be weighted before and after coating to confirm and determined the catalyst loading.

[0166] In one example the method for preparing a cathode comprises -providing a cathode support, -providing a dispersion comprising the present catalytic nanoparticles, such as a dispersion comprising Ag, Cu and / or AgCu alloy nanoparticles,

[0167] -airbrushing or ultrasonic spray coating the dispersion to the cathode support to form a catalyst layer comprising metal alloy nanoparticles on the cathode support, such as a catalyst layer comprising Ag, Cu and / or AgCu alloy nanoparticles on the cathode support.

[0168] In one example the Ag, Cu and / or AgCu alloy nanoparticles are oxidated nanoparticles, preferably surface-oxidated nanoparticles. The deposited, such as electrodeposited, catalyst films may be heat-treated in one or more heat treatment step, to induce surface oxidation, for example at 80 °C or more and / or at 100 °C or more, for example for 20 minutes.

[0169] In one example the dispersion comprising Ag, Cu and / or AgCu alloy nanoparticles comprises one or more of ionomers, binders and / or carbon powder. In one embodiment the catalyst layer comprising Ag, Cu and / or AgCu alloy nanoparticles comprises one or more of ionomers, binders and carbon powder.

[0170] In one example a cathode GDE comprises a catalyst layer comprising Ag, Cu or AgCu alloy nanoparticles and / or ionomer and / or carbon powder, on a gas diffusion layer support.

[0171] The cathode material may be or comprise non-metallic materials, such as in the case of water electrolyzers, which may comprise hydrogen evolution reaction (HER) catalyst. An example of earth-abundant HER alternative is molybdenum sulfide (M0S3), such as in the form of amorphous M0S3 nanoparticles.

[0172] The present cells or electrolyzers can be used also for carrying out hydrogen evolution reaction (HER), which is a chemical reaction that yields H2. A standard catalyst for HER, used at the anode, is platinum supported on carbon, or Pt / C.

[0173] Methods of use

[0174] The present electrolysis cells and electrolytic devices are intended to be used in one or more electrocatalytic methods or other methods including converting reactant to one or more products. These methods are considered as the normal operation of the electrolysis cells and / or the electrolytic devices. For example, a normal operation may comprise providing carbon dioxide, or other suitable reactant, to the cathode of the electrolysis cell and / or the electrolytic device, and applying electrical current to the cell or the device to produce an operating electrical potential between the cathode and the anode to reduce the reactant and to provide reaction products, such as one or more disclosed herein. The electrical current used in the normal operation may be called forward current.

[0175] The electrolysis cell, the reactor assembly or the electrolytic device may be designed and / or configured to provide or feed carbon dioxide i.e. the catholyte, to the cathode and / or water or other aqueous solution, such as a solution comprising one or more electrolytes i.e. the anolyte, to the anode. Both the catholyte and the anolyte may be flowed through the cell, for example for about 5-30 minutes, such as 5-15 minutes, before the actual reaction, such as prior to activating. The flow rates used herein, such as prior to, during and / or after activating, may be in the range of 3-10 mLmin’1cirr2, such as 3-7 mLmin’1cirr2, for example 4-6 mLmin-1crrr2.

[0176] The method may comprise either applying constant current density and measuring the potential, such as with galvanostatic / chronopotentiometry measurement, or applying a constant potential and measuring the current density, such as with potentiostatic mode or chronoamperometry measurement. Both cannot be changed at the same time. In examples used in experiments the galvanostatic mode was used.

[0177] After, and / or during, the carbon dioxide is provided to the electrolytic device and / or to the cell, electric current is applied to the electrolytic device. This may be carried out by using a fixed current, such as applied at 100-400 mA / cm2, such as 150- 250 mA / cm2. A suitable voltage may be used, such as in the range of 0.5-3.0 V, such as 0.5-3.0 V. The electric current is provided for a suitable period of time to obtain desired reaction(s), preferably a desired degree of the reaction(s) and / or reaction products, such as conversion. For example, the actual conversion of CO2 may be carried out for 30-180 minutes, such as 40-160 minutes, or continuously, preferably to obtain, detect and / or monitor desired reaction and / or reaction products.

[0178] The conversion of carbon dioxide in general may be mildly affected by the solvent, for example in the case of water as the solvent. However, with the present materials this effect can be compensated and diminished. Disclosed is a method for converting, such as reducing, carbon dioxide to products, such as to hydrocarbons, alcohols, carboxylic acids and / or to CO, the method comprising

[0179] -providing the electrolysis cell or the electrolytic device,

[0180] -providing a source of carbon dioxide,

[0181] -supplying the carbon dioxide to the electrolytic device,

[0182] -applying electric current and / or potential to the anode and the cathode to provide electrolysis to electrocatalytically reduce the carbon dioxide to generate products, and

[0183] -separating and / or recovering the generated products, such as one or more of hydrocarbons, alcohols, carboxylic acids and CO.

[0184] Disclosed is a method for converting, such as selectively converting, carbon dioxide to ethene, the method comprising

[0185] -providing the electrolysis cell or the electrolytic device,

[0186] -providing a source of carbon dioxide,

[0187] -supplying the carbon dioxide to the electrolytic device,

[0188] -applying electric current and / or potential to the anode and the cathode to provide electrolysis to electrocatalytically reduce the carbon dioxide to generate ethene, and

[0189] -separating and / or recovering the generated ethene.

[0190] Gas chromatography (GC) may be used to detect and analyse the gaseous product stream from the cell or the electrolyzer, such as shown in Figure 2. Gas chromatography can be used to analyse in real-time the product distribution of gaseous products from a performing electrolytic device. The peaks are calibrated using standard gas samples and the area under the peaks are integrated to give quantitative data. It is possible to also detect unknown products that have not been previously calibrated with standard gas samples.

[0191] FE (%) = (nxx ne-xx F) / Q x 100 where nxis the amount of product x (mol) determined by gas chromatography (GC), ne-xis the number of electrons to make x from CO2 / H2O, F is the Faraday constant (96,485 C mol-1) and Q is the total charge passed.

[0192] The method may comprise detecting the generated and / or separated product(s) and / or recovering the detected and / or separated product(s). The detection may be carried out by using any suitable methods, such as by gas chromatography, for example High Performance Liquid Chromatography (HPLC).

[0193] The source of carbon dioxide may be any suitable source which provides carbon dioxide in an amount and / or in a form that can be used and / or that can be modified into usable form and / or amount to be used in the present method. The source of carbon dioxide may comprise one or more containers, which may be equipped with controllable valves and / or actuators for controlling the flow of the carbon dioxide from the container.

[0194] The carbon dioxide, or a gas and / or solution comprising carbon dioxide, which may be called a reactant or a solution comprising the reactant comprising carbon dioxide, is provided, such as supplied, fed or conveyed, to the electrolytic device, especially to the cathode of the electrolytic device. The cathode and / or the electrolytic device may be in a cell or other container, which is arranged to receive the reactant or the solution comprising the reactant, in general in a suitable form, which may be liquid and / or gas. The reactant may be provided in an aqueous solution, such as in water, and / or in another solution, such as an electrolyte solution and / or a solution comprising organic solvent, or a combination of aqueous and organic solvents. In one example the reactant comprising carbon dioxide comprises carbonate and / or bicarbonate.

[0195] The reactant and / or the source of carbon dioxide may be provided in a suitable form, such as in the form of liquid, gas or a mixture of liquid and gas, such as humidified gas, which may be obtained by flowing gas through water, such as a water-bubbler. The reactant may comprise or be carbon dioxide. Carbon dioxide may be provided as carbon dioxide gas, and the gas may be mixed with liquid in the cell or the electrolytic device. The reactant comprising carbon dioxide and / or the source of carbon dioxide, or the catholyte, may comprise humidified CO2 gas. Any liquid may be provided from a source of liquid, which may comprise one or more containers, which may be equipped with controllable valves and / or actuators for controlling the flow of the liquid from the container.

[0196] The reactant to be provided to the anode, or the anolyte, may comprise one or more salts, such as KHCO3, for example in a concentration in a range of 5-50 mM, such as 5-15 mM, for example about 10 mM. The carbon dioxide may be converted into one or more type of reaction products, i.e. compounds, including carbon monoxide, hydrocarbons, and / or CxHyOzproducts, as well as H2 and O2 as byproducts. As the selectivity of the catalytic reaction can be controlled by using different catalytic coatings on the cathode, and optionally different cathodes, as well as controlling the reaction conditions, it is possible to obtain desired cathode reactions and / or desired reaction products, more particularly mainly the desired reaction products. The selectivity can be further controlled by controlling the reaction conditions and / or used reactants, such as by selecting a suitable source of carbon dioxide.

[0197] The hydrocarbons may comprise one or more of C1-C2 products, In the formula CxHyOz, x is a positive integer, such as 1 , 2 or 3. Variables y and z are nonnegative integers such as 0, 1 or 2 or, for example, 4, 5 or 6. Values of y and z may be equal or they can be unequal such that y may be larger than z or alternatively y may be smaller than z.

[0198] The temperature of the cell or the electrolytic device, or the liquid in the cell and / or supplemented into the cell, especially during the conversion, may be controlled and adjusted to and / or maintained at a desired range. For example, the device may be a room temperature device, and the methods may be carried out at room temperature, wherein the temperature may be in the range of 20-25 °C. However, the temperature range may be wider, ranging up to 60 °C. The temperature may be controlled by temperature controlling means arranged in a cell or the electrolytic device, such as heating means and / or cooling means, which means may be operatively connected to controlling means.

[0199] In one example the method is a method for reducing carbon dioxide to hydrocarbons comprising C1 hydrocarbons, C2 hydrocarbons or combination thereof, such as methane, ethene and / or ethane. More particularly the method may be a method for reducing carbon dioxide selectively to one or more of said products. Other minor reactions may occur, but the carbon dioxide may be reduced to obtain selectively mainly said reaction product. The methods and devices can be used for the selective conversion of CO2 to C1 or C2 compounds, such as one or more of CO, H2CO, H2CO2, CH3OH, CH4, C2H4, CH3CH2OH, CH3COOH, C2H6, and (COOH)2. In one example the method is a method for reducing carbon dioxide to ethene. The selectivity to especially ethene was experimentally associated with a catalyst comprising a combination of Ag and Cu.

[0200] In one example the method is a method for reducing carbon dioxide to CO. A selectivity to carbon monoxide was also experimentally confirmed and especially associated with Ag catalyst.

[0201] The obtained reaction products can be used for a variety of purposes, such as fuels, reagents and the like. Different reaction products can be obtained by using specific cathodes or cathode materials.

[0202] Disclosed is use of carbon dioxide for selectively preparing reaction products disclosed herein, such as the hydrocarbons and / or CO, with the methods and activated devices disclosed herein.

[0203] Examples

[0204] Example 1

[0205] Electrolyzer cell set-up

[0206] Activation methods were performed on a 5 cm2electrolyser and on a 250 cm2electrolyser using a potentiostat. The membrane electrode assembly (MEA) comprised a silver or copper cathode layer on a gas diffusion electrode, an anion exchange membrane (Sustainion) and iridium oxide (lrO2) anode. The catholyte consisted of humidified CO2 gas, and was provided with a controlled flow rate, such as 30 mLmin’1in the case of 5 cm2electrolyser and 1000 mLmin’1in the case of 250 cm2electrolyser, whilst the anolyte consisted of 10 mM KHCO3. Both catholyte and anolyte were flowed through the cell for at least 10 min prior to activation. In general flow rates were 4-6 mLmin’1cm’2.

[0207] The power sources utilized were software-controlled DC power supplies with a polarity-reversing switch. For the 5 cm2electrolyser the power source was a potentiostat Metrohm Autolab PGSTAT204 with a 10 A booster module or Metrohm VIONIC or similar. The booster increases the maximum current of the PGSTAT204 to 10 A and enables electrical impedance measurements. The activating treatments were carried out by using potential, which was reverse to the potential used in the normal operation of the electrolyzer.

[0208] The activation procedure took a total time of less than 5 minutes. However, the cell area had substantially no effect to the required activation time.

[0209] During test or performance runs, a fixed current density was applied at 200 mAcirr 2 and the voltage response was measured at 40 min intervals for total of four cycles with impedance measurements in-between each cycle. Within in each cycle, gas-chromatography samples were taken every 20 mins from the cathode.

[0210] The following table summarises the key parameters of the different activation methods on the Ag electrolyser. Activation method A not only provides the shortest time for electrolyzer stabilisation (<1 min) but also leads to the highest product selectivity towards CO (>95 %).

[0211] Table 1 . Key parameters of activation methods applied on Ag electrolyzer

[0212] *Run ended after 4 minutes due to over potential (10 V)

[0213] The following Table 2 summarises the performance parameters of the copper electrolyzer following activation using method A. The data suggests favourable selectivity towards ethene (C2H4) production.

[0214] Table 2. Performance data of copper electrolyzer following activation using method A.

[0215] Activation of Aq electrolyzer using Activation method A:

[0216] Figure 1 shows Activation method A using reverse potential applied on Ag based cathode. An initial positive linear sweep voltammetry (LSV) was applied from the open circuit potential (OCP) to 3.4 V with little increase in current density. A second sweep was applied from -2 V to 3.4 V with an onset in current density at 2.3 V. In addition, an oxidative peak was observed at around 0.25 V.

[0217] Figure 2 shows potential vs. time run at 200 mAcirr2of the Ag based cathode following Activation method A.

[0218] When the activation with Activation method A was applied to a larger 250 cm2electrolyzer cell, it was noted that the method could be upscaled without problems. In addition, this performance was run continuously for 50 hours with a stable potential around 3.6 V at a constant current density of 200 mAcm2. Though the potential was slightly higher, it was found to provide the product in the desired range. The results are shown in Figures 14 and 15.

[0219] The following methods B and C apply representative activation methods described in the literature.

[0220] Activation of Ag electrolyzer using Activation method B:

[0221] Activation Method B includes no reverse sweeps. Figure 3 shows Activation method B on Ag based cathode. Sweep rate was 5-10 mVs’1. Four consecutive positive LSVs were applied from the OCP up to 6 V with current cut-off at 200 mAcm-2. The first two LSVs achieve current densities below 50 mAcm-2at 6 V, and the second two LSVs reached 200 mAcm-2at around 5 V with an initial onset potential at 2.3 V. Figure 4 shows potential vs time run at 200 mAcm-2run on Ag based cathode following activation method B. The performance of the electrolyser at a constant current density of 200 mAcm-2proceeds with an initial surge in potential followed by a dip and then a gradual increase in potential. The initial stabilisation takes up to an hour before a potential of around 5 V is achieved which exceeds the desired potential of 3 V.

[0222] Activation of Aq based cathode using Activation method C:

[0223] Cyclic voltammetries (CVs) were applied from OCP to an upper limit of 3.4 V and a lower limit of -2.0 V for a total of twenty cycles. The CVs indicate the evolution of a reduction wave and an oxidation wave at around -1 V and 0.25 V, respectively. The on-set potential occurs at 2.2 V.

[0224] Figure 5 shows Activation method C on Ag based cathode. Sweep rate was 5-10 mVs’1. Cyclic voltammetries (CVs) were applied from OCP to an upper limit of 3.4 V and a lower limit of -2.0 V for a total of twenty cycles. The CVs indicate the evolution of a reduction wave and an oxidation wave at around -1 V and 0.25 V, respectively. The on-set potential occurs at 2.2 V. A total of 20 redox cycles were applied.

[0225] Figure 6 shows potential vs time run at 200 mAcirr2of Ag electrolyzer following activation using method C. The performance of the electrolyser at a constant current density of 200 mAcrrr2proceeds with an initial surge in potential to a value of 3.5 V before reducing back down to steady value of around 3.2 V within 10 minutes. A noticeable increment in the potential can be observed towards the end of the test run.

[0226] Control - No activation:

[0227] In the absence of any activation method, the electrolyzer exceeds 10 V within one minute under a current density of 200 mAcirr2and the performance testing was subsequently stopped. The following figures demonstrate a control performance whereby no activation is applied. The performance is later recovered using the activation method A

[0228] Figure 7 shows potential vs time run at 200 mAcm-2with no activation. In the absence of any activation method, the electrolyser exceeds 10 V within the first minute under a current density of 200 mAcm-2 and the performance testing was subsequently stopped.

[0229] Figure 1 shows recovery using activation method A. Activation using method A was applied to the failed non-activated sample. The sample undergoes similar LSV characteristics as previously described.

[0230] The following figures demonstrate that the activation method A can be applied to Cu electrolyzers.

[0231] Figure 2 shows potential vs time run at 200 mAcm-2of recovered electrolyser using activation method A. Following the reactivation using method A, the performance, at constant current density of 200 mA cm-2was recovered at a stable potential of 3 V within a minute.

[0232] Figure 8 shows how the same activation method A was used to successfully activate copper (Cu) based cathode. Figure 8 demonstrates that the re-activation undergoes a similar pattern despite being previously subjected to testing without activation.

[0233] Figure 9 shows potential vs time run at 200 mAcirr2of Cu electrolyzer. The overall poor stability, with respect to the increase in voltage, is an inherent characteristic of Cu catalysts.

[0234] Example 2

[0235] Performance data of AqCu alloy electrocatalyst

[0236] It was shown that alloys of nanoparticles can lead to improved electrocatalyst performance, such as selectivity and stability, compared to their single metal counterparts. Tuning composition of alloy between 1-10 wt% Ag and 90-99 wt% Cu could influence both selectivity and stability. The electrocatalysts could be efficiently activated with the present method.

[0237] AgCu alloys with the following compositions were provided:

[0238] AgCu-1 10:90 silver:copper alloy (wt%)

[0239] AgCu-2 1 :99 silver:copper alloy (wt%) In addition, it was experimentally confirmed that the use of ionomer / binder dispersions (5-20 wt%) including alkaline ionomers (Sustainion-X37), acidic ionomers (Nation) and Polytetrafluoroethene (PTFE) and a mixture / combination thereof, can further influence the selectivity and stability of alloy catalyst.

[0240] For 5 cm2cathode samples catalyst inks consisting of 30 mg of catalyst, 37.5 pL of 5 wt% dispersions of ionomer or ionomer mixtures and 1.5 mg carbon powder were sonicated and deposited onto the carbon paper, annealed and pre-activated in acidic or basic solutions (1 M KOH) accordingly.

[0241] Figure 10 shows activation LSVs of the AgCu-2 alloy electrocatalyst based cathode. Figure 11 shows potential vs time performance at 200 mAcm-2of the AgCu-2 alloy electrocatalyst. Performance data is presented in Table 3. The average potential is average over the specified time duration.

[0242] Table 3. Example of performance data for the AgCu alloy electrocatalyst

[0243] Other selectivities: CF , C2He < 1 %. Using Sustainion X-37 RT ionomer

[0244] The AgCu alloy electrocatalysts produce appreciable ethene (C2H4) in addition to H2 and CO. Other detectable hydrocarbons include CH4 and C2H6 <1 %

[0245] Example 3: An electrolyzer and a cathode

[0246] Figure 12A shows an example of an electrolyzer. Figure 12B shows an example of a cathode gas diffusion electrode. Figure 12C shows an example of a setup comprising an electrolyzer connected to a potentiostat / power supply. The legends are: 1. Cathode flow field plate, 2. Anode flow field plate, 3. Polymer Electrolyte Membrane, 4. Cathode gasket, 5. Anode gas diffusion electrode (GDE), 6. Cathode gas diffusion electrode (GDE), 7. Anode gasket, 8 / 9. Flow channels, 10. Inlet for catholyte, 11. Outlet for anolyte, 12. Outlet for catholyte and gaseous products, 13. Inlet for anolyte, 14. Cathode electrical connection point, 15. Anode electrical connection point. 16. Membrane electrode assembly (MEA), 17. GDE composition, 18. Macrofibrous layer, 19. Microporous layer, 20. Catalyst layer, 21. Electrolyzer, 22. Potentiostat / power supply, 23. Computer, and 24. Electrical wires.

Claims

Claims1 . A method for activating an electrolysis cell or an electrolytic device, the method comprising-providing an electrolysis cell or an electrolytic device comprising one or more electrolytic cells, preferably comprising a membrane electrode assembly, -providing a power supply, such as a potentiostat, connected to the electrolysis cell(s) to activate the electrolytic cell,-operating the power supply while monitoring the current density,-optionally measuring open circuit potential of the electrolysis cell(s),-optionally applying initial positive linear sweep voltammetry (LSV) from the measured open circuit potential to obtain an increase in current density, and -applying an activating reverse current treatment to the electrolysis cell, which reverse current is reverse to the current of the normal operation of the cell, and / or -applying an activating reverse potential treatment to the electrolysis cell, which reverse potential is reverse to the potential of the normal operation of the cell.

2. The method of claim 1 , wherein the applying the activating reverse current treatment to the electrolysis cell and / or the applying the activating reverse potential treatment to the electrolysis cell is carried out to obtain an onset in current density.

3. The method of claim 1 or 2, wherein the applying the activating reverse potential treatment to the electrolysis cell is carried out until a target current density for activation of 150 mAcm-2or more at an operational cell potential is obtained.

4. The method of any of preceding claims, wherein the activating reverse current treatment and / or the activating reverse potential treatment is selected from linear sweep voltammetry, staircase voltammetry and a potential or current step or sweep.

5. The method of any of preceding claims, wherein the activating reverse current treatment comprises applying a reverse current sweep from -200 mAcirr2to 240 mAcirr2for 5-1000 s.

6. The method of any of preceding claims, wherein the activating reverse potential treatment comprises applying a reverse potential sweep in the range of 5-100 mAcm-2for 5-1000 s.

7. The method of any of preceding claims comprising applying the activating reverse current treatment and / or applying the activating reverse potential treatment from -2—1 V to +2.9-4.0 V, such as from about -2 to about +3.4 V.

8. The method of any of preceding claims, comprising applying initial positive linear sweep voltammetry to a voltage from the open circuit potential to an upper limit in the range of 3.3-4.0 V, such as 3.3-3.8 V, for example to a voltage from the open circuit potential to an upper limit of about 3.4 V9. The method of any of preceding claims, comprising applying the initial positive linear sweep voltammetry of claim 8, and / or comprising applying the activating reverse potential treatment, with a sweep rate in the range of 40-100 mVs’1, such as in the range of 40-70 mVs’1, for example in the range of 40-60 mVs’1, or about 50 mVs’1.

10. The method of any of claims 3-9, wherein the target current density for activation is 170 mAcm-2or more, such as in the range of 170-700 mAcirr2, for example 180-220 mAcirr2.

11. The method of any of preceding claims, comprising monitoring stability of the electrolysis cell, such as by applying a galvanostatic measurement, at the target current density until the electrolysis cell performs at a stable potential of about 3 V for at least 100 minutes, such as for at least 200 minutes, for example for at least 100 hours, or for at least 500 hours determined by electrochemical voltage vs. time measurements, which indicates an activated electrolysis cell.

12. The method of any of preceding claims, comprising flowing anolyte and catholyte through the electrolysis cell(s) prior to activation, such as prior to operating the power supply while monitoring the current density, for example flowing anolyte and catholyte through the electrolysis cell(s) for at least 5 minutes, such as for 10-30 minutes.

13. The method of any of preceding claims, wherein the method is a method for recovering the performance of the electrolysis cell or the electrolytic device.

14. The method of any of claims 1-12, wherein the method is a method for activating an unused electrolysis cell or an unused electrolytic device before normal operation of the electrolysis cell or the electrolytic device.

15. The method of any of preceding claims, wherein the method is carried out in absence of gaseous streams and / or flows other than CO2 or other reactant gas, such as gases and / or vapours of one or more of isopropanol, ethanol, ammonia, N2, O2, N2H2, HCI, sulfur dioxide and / or nitrous oxide; in the absence of activating agents, such as alkali or alkali earth metal cations.

16. The method of any of preceding claims, wherein the method is carried out in the absence of electrochemical potentiostatic and / or galvanostatic polarization, overpotentials, short-circuiting, and / or cyclic voltammograms / voltammetries.

17. An activated electrolysis cell for reducing carbon dioxide to one or more products, such as to hydrocarbons, alcohols, carboxylic acids and / or to CO, comprising a membrane electrode assembly comprising-an anode, such as an anode comprising an anode catalyst layer deposited on a gas diffusion layer,-a cathode, such as a cathode comprising a cathode catalyst layer deposited on a gas diffusion layer, and-an ion exchange membrane between the anode and the cathode, wherein the electrolysis cell has been activated with the method of any of claims 1-16.

18. The method of any of claims 1-16 or the activated electrolysis cell of claim 17, wherein the membrane electrode assembly comprises a cathode comprising a metal and / or metal alloy catalyst and / or a hydrogen evolution reaction (HER) catalyst.

19. The method of any of claims 1-16 or 18 or the activated electrolysis cell of claim 17 or 18, comprising a membrane electrode assembly comprising a cathode comprising a catalyst layer comprising Ag, Cu and / or AgCu alloy, such as wherein the catalyst is a metal alloy catalyst consisting of Ag and Cu, such aswherein the catalyst layer comprises AgCu alloy nanoparticles, for example phase- separated AgCu alloy nanoparticles, preferably wherein the nanoparticles have an average particle diameter in the range of 10-50 nm.

20. The method of any of claims 1-16 or 18-19, or the activated electrolysis cell of any of claims 17-19, wherein the electrolysis cell is for a CO2 electrolytic device for reducing carbon dioxide to one or more products, or wherein the electrolytic device is a CO2 electrolytic device for reducing carbon dioxide to one or more products.

21. The method of any of claims 1-16 or 18-20, or the activated electrolysis cell of any of claims 17-20, wherein the electrolysis cell comprises a membrane electrode assembly comprising an anion exchange membrane.

22. An activated electrolytic device, such as a CO2 electrolytic device for reducing carbon dioxide to one or more products, the electrolytic device comprising-one or more activated electrolysis cells of any of claims 17-21 , preferably two or more, such as wherein the electrolysis cells are flow cells arranged as one or more stack(s), and-a power supply for providing electric current and / or potential to the electrolysis cells, and-optionally comprising one or more electronic control means for controlling the operation of the electrolytic device, such as flow control means arranged to control flow and / or pressure in the electrolytic device and / or in the electrolysis cells.

23. The activated electrolysis cell of any of claims 17-21 or the activated electrolytic device of claim 22, wherein the electrolysis cell or the electrolytic device performs at a stable potential of about 3 V for at least 100 minutes, such as for at least 200 minutes, for example at least 200 hours, or for at least 500 hours, determined by electrochemical voltage vs. time measurements.

24. The activated electrolysis cell of any of claims 17-21 or 23, or the activated electrolytic device of claim 22 or 23, wherein the activated electrolysis cell is an unused electrolysis cell.

25. The activated electrolysis cell of any of claims 17-21 or 23, or the activated electrolytic device of claim 22 or 23, wherein the activated electrolysis cell is a recovered electrolysis cell.

26. A method for converting, such as reducing, carbon dioxide to products, such as to hydrocarbons, alcohols, carboxylic acids and / or to CO, the method comprising-providing the activated electrolysis cell of any of claims 17-21 or 23-25, or the activated electrolytic device of any of claims 22-25, -providing a source of carbon dioxide,-supplying the carbon dioxide to the activated electrolysis cell or to the activated electrolytic device,-applying electric current and / or potential to the anode and the cathode to provide electrolysis to electrocatalytically reduce the carbon dioxide to generate products, and-separating and / or recovering the generated products, such as one or more of hydrocarbons, alcohols, carboxylic acids and CO.

Images