Conductive composite for electrochemical apparatus

Abstract

There is provided a composite for an electrochemical apparatus. The composite comprises a polymer selected from the list consisting of poly(halo)olefin, poly(thio)ether and polyimide, and a particulate additive, wherein the additive comprises an electrically conductive form of carbon, a metal or a mixture thereof.

Description

[0001] CONDUCTIVE COMPOSITE FOR ELECTROCHEMICAL APPARATUS

[0002] Field of the Invention

[0003] The invention relates to a composite for an electrochemical apparatus, to a method for producing a composite for an electrochemical apparatus, to an article for an electrochemical apparatus, and to an electrochemical reactor. In particular, the composite may be for three-dimensional (3D) printing, and may form the electrochemical apparatus and / or the electrochemical reactor. The composite is electrically conductive.

[0004] Background

[0005] Electrochemistry relates to electron movement in an oxidation or reduction reaction at polarized electrode surfaces. Electrochemistry spans a vast array of differing applications, including, for example, electrosynthesis, electrolysis, batteries and fuel cells. Of particular relevance to the present invention is electrosynthesis.

[0006] Electrosynthesis is the electrochemical synthesis of chemicals. Electrosynthesis has seen rapid expansion in recent years, with growing interest from both academia and industry.

[0007] One of the challenges in electrosynthesis is the manufacture of bespoke and / or intricate electrode and reactor designs. This difficulty arises from the dependency on conventional manufacturing techniques, such as milling and drilling, and the expertise required. Bespoke and / or intricate electrode and / or reactor design can be difficult to achieve, yet can be crucial to achieve optimal reaction outcomes. Thus, conventional manufacturing of bespoke and / or intricate electrode and reactor designs typically requires high levels of specialization and substantial cost.

[0008] 3D printing allows for the rapid prototyping and manufacture of bespoke and / or intricate apparatus with minimal further modification steps. When utilized alongside a cost-effective conductive printable composite, 3D printing allows the production time and development expenses to be significantly reduced. 3D printing can involve the extrusion of a thermoplastic filament; a process known as fused filament fabrication (also known as fused deposition modelling, and filament freeform fabrication). Polymers conventionally used in 3D-printing filaments include polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and thermoplastic polyurethane (TPU). A further challenge in electrosynthesis is the requirement for electrode and reactor materials to be resistant to organic solvents. Many polar organic solvents cause polymers conventionally used in 3D-printing filaments to swell and / or degrade. This makes conventional composites utilising these polymers unsuitable for use in reactors or electrodes for electrosynthesis using organic solvents.

[0009] Existing examples of conductive 3D-printing filaments use polyesters such as polyethylene terephthalate (PET), PLA or polycaprolactone (PCL) as the polymer. For example, EP3228586A1 teaches towards the use of PCL with carbon nanotubes and other conductive additives for conductive composites. However, polyesters are incompatible with organic solvents. The production of PLA-based conductive composites has been described in Electrochem. Commun., 2019, 99, 56-60; and Sustain. Energy Fuels, 2016, 4, 213-225.

[0010] US 10727537 B2 discloses 3D-printable electrode-forming compositions, and teaches towards the use of polymers such as PLA, polyethylene oxide (PEO) and polyvinyl alcohol (PVA).

[0011] CN 113561473 A discloses a 3D-printing method of preparing a polymer-based composite material containing conductive fillers and magnetic particles. The product formed by this method has a specific three-dimensional gradient structure. A pore-forming treatment is used to obtain a low-reflection and high-absorption porous electromagnetic shielding device.

[0012] CN 115256926 A discloses a 3D-printed polypropylene product that is resistant to warping, shrinkage and deformation. CN 115256926 A relates to the use of the 3D printed product in biomedical implants.

[0013] CN 113621203 A discloses a conductive 3D-printing material with improved heat resistance.

[0014] Therefore, there is a need for composites that are 3D printable, affordable, electrically conductive, and resistant to harsh reagents typically used in electrochemistry, such as organic solvents, acids, bases, oxidising agents, and / or reducing agents, and wherein the composite is able to facilitate electrochemical electrode and / or reactor design and manufacture.

[0015] Summary of the Invention

[0016] According to a first aspect, the present invention provides a composite for an electrochemical apparatus. The composite comprises: a polymer selected from the list consisting of poly(halo)olefin, poly(thio)ether and polyimide; and a particulate additive, wherein the additive comprises an electrically conductive form of carbon, a metal or a mixture thereof.

[0017] The polymer may be selected from the list consisting of: polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), thermoplastic polyimide (TPI), polyvinylidene fluoride (PVDF), and polypropylene (PP). The polymer may additionally or alternatively be selected from the list consisting of: polyaryletherketone (PAEK), polyphenylene sulfone (PPSU), polyamideimide (PAI), and fluorinated ethylene propylene (FEP). Preferably the polyolefin is PP, which has been found to display high resistance to organic solvents in the composite of the present invention. Other polymers that have demonstrated high resistance to organic solvents in the composite of the present invention include PAEK (e g. PEEK, PEKK), PPS, PEI, TPI, PEI, PAI, and FEP. PEEK, PEKK, PPS and FEP showed the widest ranging resistance.

[0018] Examples of electrically conductive forms of carbon include glassy carbon (GC) powder, graphene nanoplatelets (GnP) powder, and carbon black (CB).

[0019] Preferably, the particulate additive is a mixture of one or more electrically conductive forms of carbon and / or one or more metals. More preferably the particulate additive is a mixture of GnP and CB (e.g. extra-conductive carbon black, ECB).

[0020] At least one additive may be a metal. The metal may be silver, nickel, or an alloy (e.g. stainless steel). Preferably, the metal is nickel.

[0021] The composite of the present invention is electrically conductive, more resistant to organic solvents, lower in cost, and 3D printable. The composite can be used to manufacture an apparatus for electrochemistry, such as an electrochemical reactor and / or an electrode, offering a cost- effective alternative to traditional electrode materials with significantly improved customizability.

[0022] As discussed above, polar organic solvents degrade polymers that are conventionally used for 3D printing, such as PET, PLA, ABS, and TPU. Chemically resistant composites for electrochemical apparatuses, as provided by the present invention, are crucially important.

[0023] Surprisingly, in comparison to conventional 3D printing composites, the composites of the present invention can demonstrate high resistance to organic solvents. It is particularly surprising that the composite of the present invention demonstrates superior resistance to organic solvents when compared to the polyolefin itself. This is particularly the case where the additive is an electrically conductive form of carbon.

[0024] It has also surprisingly been found that the combination of two or more additives can further enhance the conductivity of the composite, compared to a composite containing any one additive alone or compared to the sum of the conductivities of each additive in a composite. This may be described as a synergistic effect. This has specifically been observed when using two carbonbased additives, GnP and ECB, in PP.

[0025] While the prior art discusses composites for 3D printing, the prior art has not previously recognised an ability to prepare and use such composites for electrochemical equipment, such as electrodes. Furthermore, there is no disclosure of a composite that can be formed into a filament that meets these requirements.

[0026] For instance, US2020 / 0130265A1 discloses a powder material for 3D printing. The powder material includes a plurality of particles that have a polymeric matrix containing a loading of graphene nanoplatelets. There is no suggestion that this powder could be used to form a filament, or used in fused filament fabrication. There is also no discussion of the use of the powder material in an electrochemical apparatus.

[0027] US10727537B2 teaches towards the use of polymers such as PLA, polyethylene oxide (PEO) and polyvinyl alcohol (PVA). The inventors have identified that each of these polymers are incompatible with organic solvents.

[0028] CN113561473A also teaches towards the use of polymers that have problems in relation to degradation in organic solvents used in electrochemistry.

[0029] CN115256926A does not mention applications relating to electrochemical apparatuses.

[0030] CN113621203A focusses on the heat resistance of composites, there is no mention of solvent resistance or electrical conductivity. Furthermore, CNI 13621203A does not mention applications relating to electrochemical apparatuses.

[0031] According to a second aspect, the present invention provides a method for producing a composite, wherein the composite is for electrochemical apparatus. The method comprises: providing a polymer selected from the list consisting of poly(halo)olefin, poly(thio)ether and polyimide, providing a particulate additive, wherein the additive comprises an electrically conductive form of carbon, a metal or a mixture thereof, combining the polymer with the particulate additive to provide a composite precursor, and heating the composite precursor to melt the composite precursor and form the composite.

[0032] The composite of the first aspect may be obtainable (e.g. obtained) by the method of the second aspect.

[0033] The method of the second aspect provides benefits in terms of the physical structure of the produced composite. It was found that solution mixing of the components of the composite followed by addition of an anti-solvent to precipitate the composite formed the composite with a porous, sponge-like structure that was not suitable for 3D printing.

[0034] By contrast, the method of the second aspect provides a homogenous and non-porous composite that is suitable for 3D printing.

[0035] The composite may be suitable for manufacture and / or processing into electrochemical apparatus. This manufacture and / or processing may include 3D-printing, injection moulding and / or compression moulding. These techniques do not require milling and / or drilling, and hence facilitate the production of complex shapes for apparatus such as electrodes. Preferably the composite is for 3D-printing.

[0036] The step of combining the polymer with the particulate additive to provide a composite precursor may comprise mixing the solid polymer with the particulate additive. This is particularly suitable for polymers that are poorly soluble in organic solvents.

[0037] Preferably the step of combining the polymer with the particulate additive comprises solution mixing, for example wherein the step comprises: dissolving the polymer in an organic solvent to form a solution of the polymer in the organic solvent, dispersing the particulate additive in the solution so as to provide a dispersion, and cooling the dispersion and / or adding an anti-solvent to the dispersion to precipitate the composite precursor. The method may comprise separating (e.g. by filtration) the composite precursor from the organic solvent and any anti-solvent. When the method of the second aspect includes these preferable steps, further benefits can be attained in terms of the accuracy with which the amounts of each component in the composite can be controlled and the safety of operators manufacturing such a composite. It was found that melt-mixing the components of the composite caused the additive to become airborne, consequently altering the amount of additive in the composite and providing risks to the safety of the operator.

[0038] The method of the second aspect enables the composite to be formed with accurate amounts of additive and poly(halo)olefin (or ratios thereof), and reduces the risk to the operator.

[0039] Preferably the composite is extruded after it has been melted. The composite precursor may be heated (and melted) in an extruder. The composite may be cooled after it has been melted, for example after it has been extruded.

[0040] According to a third aspect, the present invention provides an article comprising the composite of the first aspect. The article may be an electrochemical apparatus, such as an electrochemical reactor or a part thereof, such as an electrode. The article may be a sensor, battery, or a fuel cell, or a part thereof. The article may be formed by 3D printing the composite.

[0041] The present invention allows articles to be formed more readily by 3D printing using the composite of the first aspect. In particular, the present invention provides particular benefits in terms of facilitating the manufacture of bespoke and / or intricate designs of electrochemical apparatuses. Such apparatuses may be prepared rapidly and for a fraction of the cost of conventional electrochemical apparatuses.

[0042] According to a fourth aspect, the present invention provides an electrochemical screening apparatus for simultaneously screening a plurality of electrochemical reactions. It will be understood that, in use, the electrochemical reactions are chemically isolated from one another. The electrochemical screening apparatus comprises: (a) a body comprising a plurality of cavities, and (b) a plurality of pairs of electrodes, wherein the electrodes of each pair are electrically isolated from one another, wherein each pair of electrodes is physically connected to one another, and wherein the electrodes of each pair are separately electrically connected to the electrodes of another pair. Each pair of electrodes is configured in relation to one of the cavities such that, in use when there is an electrolyte in the cavity, the electrolyte can make electrical contact between the electrodes of the pair of electrodes in the cavity. Each pair of electrodes may be held by one or more electrode mountings in the wall of each cavity and / or by a head, wherein the head can be configured to hold electrodes that extend into the cavity. The electrodes may be elongate. The electrodes may extend in the same direction as one another. The electrochemical screening apparatus may therefore comprise a plurality of physically connected electrode mountings (e g. heads) and a plurality of pairs of electrodes coupled to the electrode mountings. One pair of the pairs of electrodes may extend from each electrode mounting. The cavities are for holding a reaction mixture, which typically comprises a liquid.

[0043] Preferably the electrodes are formed of the composite of the first aspect. Preferably the electrodes and the electrically connecting portion of the electrode mounting are formed of the composite of the first aspect.

[0044] The body may be a base, and the cavities may be wells. Therefore, the electrochemical screening apparatus may comprise a base, wherein the base comprises a plurality of chemically and electrically isolated wells. The wells may be configured to each simultaneously receive a pair of the elongate electrodes.

[0045] The body may be a well plate. The heads may be arranged in an array that is complementary to the arrangement of the cavities, such that when the heads are placed over the cavities, each head can sit over a different cavity.

[0046] According to a fifth aspect, the present invention provides an electrochemical apparatus comprising a head, a body, and a pair of elongate electrodes, wherein the body is able to rotate about an axis relative to the head, and wherein the body and the head are secured to one another. One or both of the electrodes is or are configured to rotate with the body. The electrodes extend in substantially the same direction as one another. The direction in which the electrodes extend is substantially parallel with the axis of rotation, and the electrodes are electrically isolated from one another. It will be understood that the electrodes are electrically isolated from one another when no electrolyte is present; but electrolyte will electrically connect the electrodes. It will be understood that the electrodes have an electrode surface that, in use, contacts a reaction mixture. The electrode surface typically extends in a direction substantially parallel with the axis of rotation to provide efficient contact between the electrode and the reaction mixture. Furthermore, the electrode surface typically extends in three dimensions to provide efficient contact between the electrode and the reaction mixture. The electrodes may each independently be electrically connected to a terminal in the head. In other words, a first electrode can be connected to a first terminal in the head and a second electrode can be connected to a second terminal in the head. Preferably, in use, the rotation of the or each electrode causes the or each electrode to move through a reaction mixture. This rotation can create turbulence within the reaction mixture, enhancing the mixing of the reaction mixture and enhancing the exchange of species at and near the electrode surface.

[0047] The present inventors are not aware of any investigation into the effect of such an apparatus on an electrochemical reaction.

[0048] Conventionally, rotating electrodes have found application in analytical techniques, as rotating disk electrodes, rather than for performing chemical reactions for synthetic purposes. It will be understood that rotating disk electrodes only have a two-dimensional electrode surface that extends in a direction perpendicular to the axis of rotation, rather than a direction parallel to the axis of rotation. Furthermore, rotating disk electrodes rotate within a reaction mixture rather than moving through a reaction mixture.

[0049] It has surprisingly been found that a reactor of the fifth aspect can increase the yield of electrochemical reactions, compared to using conventional apparatus comprising static electrodes or using a stirrer bar to mix the reaction mixture.

[0050] This enhanced performance may be attributed to improved mass transport as a result of the rotation of the electrode, and also an increased surface area, which may allow lower current densities to be used for a given reaction than was possible with a conventional (non-rotatable) apparatus. Lower current densities may mitigate the effect of intermolecular reactions.

[0051] Rotational movement of the electrode may facilitate the rapid replenishment of the starting material on the electrode surface, and limit the amount of overoxidation or overreduction of the reaction materials.

[0052] The apparatus may be configured such that the first and second electrodes are able to co-rotate, i.e., rotate about an axis in the same direction. The first and second electrodes may be mechanically attached to one another

[0053] The apparatus may be configured such that the first and the second electrodes are able to contrarotate (counter-rotate), i.e. rotate about an axis in opposite directions to one another. The apparatus of the fifth aspect may be configured such that one electrode of the pair of electrodes does not rotate while the other electrode rotates. The apparatus of the fifth aspect may comprise a first body with which a first electrode of the pair of electrodes is attached to or unitary with, and a second body with which a second electrode of the pair of electrodes is attached to or unitary with, and wherein the apparatus is configured such that the first electrode and / or the second electrode can rotate about an axis.

[0054] Each electrode may include one or more apertures and / or protuberances, for example to increase the surface area of the electrode. The apparatus may comprise a plurality of pairs of electrodes. The apparatus may comprise a plurality of anodes and / or a plurality of cathodes. The pairs and / or the anodes and cathodes may be arranged in alternating spaced layers and / or arranged in an alternating spaced circumferential pattern. The pairs may be configured to rotate and / or physically connected to the body.

[0055] JPS60137922A discloses a rotatable cylindrical electrode for preparing thin polymer films by electrolytic polymerisation. However, there is no teaching of being able to increase the rate and / or yield of reaction when electrodes are rotated compared to when they are not rotated. JPS60137922A teaches towards the anode being rotatable about a shaft and the cathode being fixed. There is no disclosure of reciprocation of the direction of rotation. There is no disclosure of both electrodes being configured to corotate or contra-rotate and the electrodes alternating in polarity around the circumference of the rotation or being arranged in alternating layers. There is no disclosure of apertures through the electrodes or protuberances in the surface of the electrodes. Furthermore, there is no disclosure of both electrodes having a terminal in the head.

[0056] The inventors have surprisingly shown that the electrochemical apparatus of the fifth aspect can provide even higher yields when the direction of rotation of the electrodes is alternated (i.e. when the rotation is reciprocated), compared to when the electrodes are continuously rotated in a single direction. The apparatus may be configured such that the direction of rotation of the first and / or second electrodes may be changed. Rotation preferably refers to rotation such that, in use, the electrode is moved through the reaction mixture.

[0057] According to a sixth aspect the claimed invention provides a method of operating an electrochemical reactor comprising a pair of electrodes, wherein one or both of the electrodes is or are configured to move, wherein the method comprises, whilst the electrodes are in contact with a reaction medium, and whilst a potential difference is applied across the electrodes, moving one or both of the electrodes through the reaction mixture in a first direction, and moving the one or both of the electrodes through the reaction mixture in a second direction. Preferably the first direction and the second direction are opposite to one another. Preferably the method comprises repeating the movement in the first direction and the movement in the second direction two or more, such as 10 or more, or 100 or more, times. Preferably one or both of the electrodes are specifically configured to rotate such that they move through the reaction medium. Preferably the first direction and the second direction correspond to clockwise rotation and anticlockwise rotation. Preferably the method of the sixth aspect uses the apparatus of the fifth aspect.

[0058] One or more electrodes may form a hollow cylinder. The hollow cylinder may be centred on the axis of rotation.

[0059] Each electrode may be formed from a single piece or may be formed of two or more segments. The segments may be joined together with one or more supports. The supports may be concentric bands formed of the same material as the electrodes.

[0060] The electrodes may extend from the base in a concentric pattern, such as a pattern of concentric rings.

[0061] The apparatus may comprise a means to enable rotation, such as a motor.

[0062] Preferably, the rotating electrode may be designed such that it may be used in an inert atmosphere. For example, designed such that it would fit as a standard Schlenk tube, such as because it has a ground glass joint. Ground glass joints are typically conically tapered (e g. a 1: 10 taper). The ground glass joint may be male or female. The maximum diameter of the ground glass joint may be 19mm, 24mm, 29mm or 34mm. Preferably the ground glass joint is female and has a maximum diameter of 29mm.

[0063] According to a seventh aspect, the present invention provides an electrochemical flow cell. The electrochemical flow cell comprises a fluid inlet, a fluid outlet, and two sheets of electrically isolating material, wherein the two sheets of electrically isolating material are spaced apart by a pair of electrodes, wherein the electrodes are interdigitated with one another, wherein the electrodes are electrically isolated from one another, and wherein a void between the interdigitations of the electrodes defines a conduit that allows fluid to pass from the fluid inlet to the fluid outlet.

[0064] According to an eighth aspect, the present invention provides an electrochemical flow cell. The electrochemical flow cell comprises a conduit and a pair of electrodes, wherein each electrode defines a plurality of sections of the inner surface of the conduit, and wherein the sections are arranged along the length of the conduit and alternate between the electrodes along the length of the conduit, and wherein electrically isolating material separates the electrodes such that, in use, where a potential difference is applied across the electrodes, a fluid flowing through the conduit is exposed to an alternating potential difference as it flows through the conduit. In use, the flow cell of the eighth aspect can expose a fluid flowing through the conduit to a “pseudo alternating polarity” of potential difference, akin to rapidly switching the polarity of the electrodes. It will be understood that this pseudo alternating polarity can be achieved with constant (i.e. direct current) potential difference. The disruption of the diffuse layer can enhance mixing and / or improve mass transport. The electrodes may both be located on one side of the conduit. Preferably the electrodes are interdigitated, for example to enable the sections of both electrodes to be arranged on the same side of the conduit. The flow cell of the eighth aspect may comprise a fluid inlet and a fluid outlet that are fluidly connected via the conduit.

[0065] Achieving such a design via conventional manufacturing would be challenging, and precisely machining interdigitated electrodes would prove both timely and costly. Therefore, there is a benefit to making this reactor using the composite of the present invention.

[0066] Conventional electrochemical flow cells are prohibitively expensive and complex. Most conventional electrochemical flow cells utilise plate electrodes separated by pre-cut spacers.

[0067] However, the present invention allows for relatively simple-to-use electrochemical flow cells to be produced cheaply.

[0068] The flow cell can be configured such that the sheets can be transparent or translucent. The electrically isolating material may transmit ultraviolet (UV), visible and / or infrared radiation. For example, the electrically isolating material may be polypropylene. This may enable a reaction to be performed and / or monitored using such radiation. The electrochemical reactor may be a photoelectrochemical flow cell.

[0069] The design of electrochemical flow reactors that are able to transmit ultraviolet, visible and / or infrared radiation has been a challenge because electrodes do not transmit UV, visible and / or infrared radiation, and are traditionally configured as the sheets that sandwich the electrically isolating material.

[0070] The composite of the present invention has shown that photoelectrochemical flow cells can be manufactured that can transmit UV, visible and / or infrared radiation and that provide particular benefits in terms of performing and / or monitoring electrochemical reactions using UV, visible and / or infrared radiation. In use, the interdigitation of the electrodes can alternate the electrical polarity that the fluid flowing through the conduit is subjected to, as the fluid passes from one interdigitation to another.

[0071] Furthermore, the productive electrode surface area is much greater than for conventional plate electrodes, requiring less electrode material and / or providing a greater active surface area for a given amount of electrode material.

[0072] The flow of the fluid over the electrode surfaces provides rapid replenishment of the electrode surface, improving the mixing within the reactor and preventing over oxidation or over reduction of reaction materials.

[0073] Each sheet of electrically isolating material may comprise one or more conduits for temperature control fluid (e g. water). Water-cooled photoelectrochemical flow cells, have been shown to allow higher currents than those used in standard photoelectrochemical flow cells to be utilised, thereby providing increased productivity.

[0074] Two or more of the flow cells may be fluidly connected in series (e.g. stacked on top of one another). For example, the polarity of the electrodes of two adjacent flow cells may be alternated with respect to one another. A portion of fluid exposed to the anode in one flow cell may be exposed to the cathode in the next flow cell (and vice versa). This has been shown to increase product yield, possibly due to enhanced mixing in comparison to standard (photo)electrochemical flow cells.

[0075] Preferably the electrodes of the electrochemical screening apparatus of the fourth aspect, the electrochemical apparatus of the fifth aspect, the method of the sixth aspect, and the electrochemical flow cell of the seventh aspect are each independently made of the composite of the first aspect.

[0076] The ability to produce such apparatus using the composite of the first aspect can provide substantial cost savings as well as benefits in terms of the functionality, as discussed above. Electrochemical apparatuses based on the composites of the present invention may be fabricated at a fraction of the cost of traditional electrochemical apparatuses. With these notable cost reductions, the composite of the present invention can significantly increase the affordability of electrochemical apparatus. The present invention enables bespoke and innovative configurations to be quickly prototyped with minimal user input, ranging from simple interdigitated flow paths to complex multileveled flow cubes. Detailed Description

[0077] Composite

[0078] The invention provides a 3D-printable composite for an electrochemical apparatus. The composite is as defined by the first aspect. The composite may comprise a poly(halo)olefin and a particulate additive, wherein the additive is an electrically conductive form of carbon, a metal or a mixture thereof.

[0079] The composite may consist essentially of, or consist of, one or more poly(halo)olefins and one or more particulate additives, wherein the particulate additives are selected from conductive forms of carbon and metals.

[0080] Polymer

[0081] The polymer is a poly(thio)ether, a polyimide and / or a poly(halo)olefin. The polymer may be a thermoplastic polymer. The polymer may be a halopolymer, such as a fluoropolymer.

[0082] The term poly(halo)olefin may refer to a polyhaloolefin (e.g. a polyfluoroolefin) and / or a polyolefin. The polyolefin may be a polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, or a copolymer thereof (especially an ethylene-octene copolymer or a propylene -butene copolymer). The polyolefin may be a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), a very low density polyethylene (VLDPE), an ultra low density polyethylene (ULDPE), a medium density polyethylene (MDPE), polypropylene, polymethylpentene (PMP), polybutene-1 (PB-1), an ethylene-octene copolymer, a stereo-block PP, an olefin block copolymer, a propylene -butane copolymer, an ethylene propylene diene monomer rubber or a combination thereof. The polyolefin may be an elastomer, such as a polyisobutylene (PIB), a poly(a-olefin), an ethylene propylene rubber (EPR), or a combination thereof. The poly(halo)olefin may be a polyfluoroolefin, such as polyvinylidene fluoride (PVDF) or fluorinated ethylene propylene (FEP).

[0083] The term poly(thio)ether encompasses polyethers and polythioethers. Polyethers include polyetherimide (PEI, e.g. ULTEM 9085), polyphenyl sulfone (PPSU), and polyetherketones, such as polyaryletherketones (e.g. polyetheretherketone (PEEK) and polyetherketoneketone (PEKK)). Polythioethers include polyarylthioethers (e g. polyphenylene sulfide (PPS)). All of the above groups may be considered poly(thio)ethers as they all comprise ether or thioether groups.

[0084] Polyimides include PEI and thermoplastic polyimide (TPI, e g. Sabie EXTEM™). Polyimides may include polyamideimides (PAI).

[0085] Preferably the polymer comprises and / or consists of groups selected from the list consisting of: hydrocarbon (including aryl, alkyl, alkenyl, alkynyl), (thio)ether (including ether and thioether), ester, sulfone, halogen (especially fluoride), ketone, imide and amide.

[0086] Polymers such as PAEK, PEEK, PEKK, PPS, PPSU, PEI (e.g. ULTEM 9085), TPI (e.g. Sabie EXTEM™), PVDF and FEP are considered in the art to be engineering and / or high / ultrahigh performance polymers. Their performance and solvent resistance may be further improved by the inclusion of additives, as in the present invention.

[0087] Out of the polymers tested, PEEK, PEKK, PPS, and FEP based composites therefore appear to show the widest range of durability to typical organic solvents used in electrochemistry.

[0088] It is considered that the composite provides particular benefits with polymers in the PAEK family (including PEEK and PEKK).

[0089] Preferably the polyolefin consists essentially of, or consists of, carbon and hydrogen atoms. For example, the polyolefin may not comprise polymerised acrylonitrile monomers.

[0090] The polymer (e.g. poly(halo)olefin) may be a homopolymer or a copolymer (e.g. an alternating copolymer, a random copolymer, a block copolymer or a graft copolymer). The composite may comprise a mixture of a poly(halo)olefin and another polymer, for example a mixture of two or more poly(halo)olefins.

[0091] Preferably, the polymer is polypropylene, which has been found to display high resistance to organic solvents including methylene chloride (DCM) and tetrahydrofuran (THF).

[0092] The at least one poly(halo)olefin may have a repeat unit with the general formula (CH2CR1R2)n, wherein R1and R2are independently selected from H, Ci-Cio alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C&-C aryl, and halogen. Preferably R2is selected from H and halogen, n may be 10 or more, such as 100 or more, or 500 or more. Alkyl groups may be straight-chain or branched. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neo-pentyl, isoamyl, hexyl, heptyl, octyl, and nonyl. Alkyl groups may be C1-C8, such as C1-C6, or C1-C4, preferably Cl, C2 or C3.

[0093] Alkenyl groups contain one or more carbon-carbon double bond. Alkenyl groups may contain alkyl portions. Alkenyl groups may be straight-chain or branched. Examples of alkenyl groups include propenyl, butenyl, pentenyl, hexenyl, cyclohexenyl, and septenyl. Alkenyl groups may be C2-C8, such as C2-C6, or C2-C4, such as C3.

[0094] Alkynyl groups contain one or more carbon-carbon triple bond. Alkynyl groups may contain alkenyl and / or alkyl portions. Alkynyl groups may be straight-chain or branched. Alkynyl groups may be C2-C8, such as C2-C6, or C2-C4, such as C3.

[0095] Aryl groups contain one or more aromatic carbon ring, such as a phenyl ring. Aryl groups may contain alkyl, alkenyl and / or alkynyl portions. Alkynyl groups may be C6-C8, such as C7, for example benzyl.

[0096] Each halogen may represent fluorine, chlorine, bromine or iodine. Preferably each halogen is fluorine or chlorine, especially fluorine.

[0097] R1and R2may independently be selected from H, Ci-Cs alkyl, C2-C8 alkenyl, C2-C8 alkynyl, Cs- Cs aryl, and halogen. R1and R2may independently be selected from H, Cj-Cs alkyl, C2-C6 alkenyl, C2-C6 alkynyl, Ce-C? aryl, and halogen. R1and R2may independently be selected from H, C1-C4 alkyl, C2-C4 alkenyl, Ce-C? aryl, and halogen.

[0098] Preferably R2is H or halogen. For example, R1may be selected from H, Ci-Cs alkyl, C2-C8 alkenyl, C2-C8 alkynyl, Ce-Cs aryl, and halogen, and R2may be H or halogen. R1may be selected from H, C1-C4 alkyl, C2-C4 alkenyl, Ce-C? aryl, and halogen, and R2may be H or halogen.

[0099] The composite may comprise the polymer in an amount of 5% or more by weight, such as 20% or more, such as 30% or more, preferably 40% or more, or 50% or more, more preferably 60% or more, such as 70% or more, or 80% or more by weight. Composites have been successfully formed with amounts of polymer as low as 15wt%. Particularly low weight percentages of polymer can be used when the additive is a metal, as metals tend to have a high density (especially platinum). The composite may comprise the polymer in an amount of 99% or less by weight, or 98% or less, preferably 97% or less, such as 96% or less, or 95% or less, more preferably 92% or less, for example 90% or less, or 85% or less, such as 80% or less, or 75% or less by weight, such as 50% or less, or 30% or less, or 20% or less, such as 15% or less by weight. The composite may comprise the polymer in an amount of from 5% to 98%, such as from 40% to 97%, or from 60% to 92% by weight. Lower amounts of the polymer have been shown to be preferable to allow higher amounts of the particulate additive to be included in the composition, which increases the conductivity of the composite. However, higher amounts of polymer can provide structural benefits to the composite, for example making the composite more robust and / or less brittle.

[0100] Preferably the polymer is polypropylene and the composite comprises polypropylene in an amount of 5% or more by weight, such as from 20% to 98%, such as from 40% to 97%, or from 60% to 92% by weight.

[0101] Particulate Additive

[0102] The composite comprises a particulate additive that comprises an electrically conductive form of carbon, a metal or a mixture thereof.

[0103] Composites have been shown to be conductive with amounts of additives as low as 5 wt%. The composite may comprise the additive in an amount of 1% or more by weight, such as 2% or more, preferably 3% or more, such as 4% or more, or 5% or more, more preferably 8% or more, or 10% or more, for example 12% or more, or 15% or more, such as 20% or more, or 25% or more, or 30% or more, such as 35% or more by weight. Composites have been successfully formed with amounts of additives as high as 90 wt%. The composite may comprise the additive in an amount of 95% or less by weight, such as 92% or less, or 90% or less, or 80% or less, such as 70% or less, or 50% or less by weight. The amount of the additive may be from 1% to 95% by weight, such as from 3% to 95%, or from 8% to 92% by weight.

[0104] The additive may be a conductive form of carbon. The conductive form of carbon may comprise a metal coating, for example metal-coated carbon fibre (especially nickel-coated carbon fibre). The metal coating may be a metal selected from Ag, Au, Fe, Zn, Pt, Ni, Al, Bi, Sn, Sb, Pb, Ag, In, Cu and Cr, and alloys thereof. Alloys may include BiSnPb, BiSn, BiSnAg, SbPbBi, SnBi, InSn, SnlnAg, SnAgCu, SnAg, SnCu, SnSb, SnAgSb, and mixtures thereof. Preferably the metal is selected from the list consisting of Ag, Fe, Cr and Ni, and alloys thereof. More preferably the metal is selected from the list consisting of Ag, steel (e.g. stainless steel), and Ni. Yet more preferably the metal is Ag and / or Ni. The skilled person will appreciate that certain forms of carbon (e.g. undoped diamond) are not conductive, and will appreciate the conductive forms of carbon that are suitable to be used with the claimed invention. The conductive form of carbon may be an allotrope of carbon. It will be understood that the conductive form of carbon does not encompass polymers, for example, which contain carbon but are not forms of carbon.

[0105] The composite may comprise the conductive form of carbon in an amount of 1% or more by weight, such as 2% or more, preferably 3% or more, such as 4% or more, or 5% or more, more preferably 8% or more, or 10% or more, for example 12% or more, or 15% or more, such as 20% or more, or 25% or more, or 30% or more, such as 35% or more by weight. The composite may comprise the conductive form of carbon in an amount of 90% or less by weight, such as 80% or less, or 70% or less, or 65% or less, such as 50% or less, or 45% or less by weight, for example 40% or less by weight. The amount of the conductive form of carbon may be from 1% to 90% by weight, such as from 3% to 70%, or from 3% to 45% by weight.

[0106] The conductive form of carbon may be selected from the list consisting of: amorphous carbon (e.g. activated carbon and / or carbon black (CB, which may be described as electroconductive carbon black, and / or extra-conductive carbon black (ECB), such as PRINTEX® XE2-B or Ketjenblack EC-600JD, and / or ultra-conductive carbon black (UCB)), graphite, graphene (e.g. graphene nanoplatelets (GnP)), glassy carbon (GC), carbon nanotubes, carbon fibres (e.g. carbon nanofibers), fullerenes, doped diamond (such as boron doped diamond), and conducting polymers. Carbon black may be defined as having an amorphous carbon content of 90% or more by weight, such as 97% or more by weight. Preferably the conductive form of carbon is selected from the list consisting of: ECB, GC and GnP. More preferably, the conductive form is carbon is ECB and / or GnP.

[0107] The composite may comprise the conductive form of carbon in an amount of 1% or more by weight, wherein the conductive form of carbon is selected from the list consisting of: amorphous carbon (e g. activated carbon and / or carbon black (which may be described as electroconductive carbon black, extra-conductive carbon black (ECB), and / or ultra-conductive carbon black (UCB)), graphite, graphene (e.g. graphene nanoplatelets (GnP)), glassy carbon (GC), carbon nanotubes, carbon nanofibers, fullerenes, doped diamond (such as boron doped diamond), and conducting polymers.

[0108] It has been identified that the combination of two or more electrically conductive forms of carbon may synergistically enhance the conductivity of the composite. The composite may comprise a mixture of two or more conductive forms of carbon, for example selected from the list consisting of: amorphous carbon (e.g. activated carbon and / or carbon black (CB, which may be described as electroconductive carbon black, and / or extra-conductive carbon black (ECB)), graphite, graphene (e.g. graphene nanoplatelets (GnP)), glassy carbon (GC), carbon nanotubes, carbon nanofibers, fullerenes, doped diamond (such as boron doped diamond), and conducting polymers. Preferably the composite comprises two or more conductive forms of carbon selected from the list consisting of: amorphous carbon (e.g. CB), GC and graphene (e.g. GnP).

[0109] More preferably the composite comprises a mixture of amorphous carbon (e.g. CB) and GC. The mixture of amorphous carbon (e.g. CB) and graphene (e.g. GnP) may comprise the amorphous carbon in a proportion of 25% or more by weight relative to the total weight of amorphous carbon (e.g. CB) and graphene, such as 40% or more, or 60% or more, such as 70% or more, or 80% or more by weight. The proportion of amorphous carbon may be 99% or less, such as 98% or less, such as 95% or less, or 90% or less by weight. The proportion of amorphous carbon may be from 25% to 99% by weight, such as from 40% to 98%, or from 60% to 95% by weight.

[0110] The composite may comprise GC in an amount of 30% or more, preferably 40% or more, such as 45% or more, preferably 50% or more, such as 55% or more by weight. The amount of GC may be 80% or less, such as 70% or less, or 60% or less. For example, the amount of GC in the composite may be from 30 to 80 wt%, or from 50% to 80% by weight.

[0111] The composite may comprise graphene (e g. GnP) in an amount of 2 wt% or more, such as 5 wt% or more, or 8 wt% or more, such as 10 wt% or more, or 15 wt% or more, for instance 20 wt% or more, or 30 wt% or more by weight. The composite may comprise graphene (e.g. GnP) in an amount of 70% or less, such as 50% or less, or 40% or less by weight. The amount of graphene (e.g. GnP) in the composite may be from 2 to 70 wt%, such as from 5 to 50 wt%, for example from 20 to 40 wt%.

[0112] The composite may comprise amorphous carbon (e.g. CB, such as ECB or UCB) in an amount of 1 wt% or more, or 2 wt% or more, such as 5 wt% or more, or 10 wt% or more, such as 12 wt% or more. The amount of amorphous carbon may be 70 wt% or less, such as 50 wt% or less, or 40 wt% or less, for example 30 wt% or less. The amount of amorphous carbon may be from 1 to 70 wt%, such as from 2 to 50 wt%, or from 12 to 30 wt%.

[0113] The additive may be a metal. It has been identified that the combination of two or more metals may synergistically enhance the conductivity of the composite. The additive may comprise two or more metals. The metal may be an alloy of two or more metals. The metal may be selected from the list consisting of: Ag, Au, Fe, Zn, Pt, Ni, Al, Bi, Sn, Sb, Pb, Ag, In, Cu and Cr, and alloys thereof. Alloys may include BiSnPb, BiSn, BiSnAg, SbPbBi, SnBi, InSn, SnlnAg, SnAgCu, SnAg, SnCu, SnSb, SnAgSb, and mixtures thereof. Preferably the metal is selected from the list consisting of Ag, Fe, Cr and Ni, and alloys thereof. More preferably the metal is selected from the list consisting of Ag, steel (e.g. stainless steel), and Ni. Yet more preferably the metal is Ag and / or Ni.

[0114] The composite may comprise the metal in an amount of 20% or more by weight, such as 30% or more, preferably 35% or more, such as 40% or more, or 45% or more, more preferably 50% or more by weight. The composite may comprise the metal in an amount of 98% or less by weight, such as 95% or less, or 92% or less, for example 90% or less, such as 80% or less, or 70% or less by weight. The amount of the metal may be from 20% to 98% by weight, such as from 30% to 95%, or from 40% to 90% by weight.

[0115] The composite may comprise stainless steel in an amount of 10% or more, such as 20% or more, or 30% or more, for example 40% or more by weight. The amount of stainless steel may be 98% or less, such as 95% or less, or 90% or less, such as 85% or less, or 80% or less by weight. The amount of stainless steel may be from 10 to 98%, such as from 30% to 90%, or from 40% to 80% by weight.

[0116] The composite preferably comprises nickel in an amount of 40% or more, such as 50% or more, or 55% or more, for example 60% or more, or 70% or more, such as 80% or more by weight. The amount of nickel may be 98% or less, such as 95% or less, or 92% or less, such as 90% or less by weight. The amount of nickel may be from 40 to 98%, such as from 50 to 95%, or from 60 to 95%, more preferably from 80% to 95% by weight.

[0117] The composite preferably comprises silver in an amount of 10% or more, such as 20% or more, or 30% or more, for example 35% or more, or 40% or more, such as 50% or more by weight. The amount of silver may be 98% or less, such as 90% or less, or 80% or less, such as 70% or less by weight. The amount of nickel may be from 10 to 98%, such as from 30 to 90%, or from 30 to 70%.

[0118] The particles of the additive may have an average diameter of lOnm or more, such as 20nm or more, or 50nm or more, such as lOOnm or more, or 500nm or more. The average diameter of the particles may be 500pm or less, such as 100pm or less, such as 50pm or less, preferably 40pm or less, such as 30pm or less, or 20pm or less, for example 15 pm or less, more preferably 10 pm or less, for example 7 pm or less, or 5 pm or less, such as 2 pm or less, or 1 pm or less. The average diameter of the particles may be from lOnm to 500pm, preferably from lOnm to 40pm, more preferably from lOnm to 10pm, or from lOnm to 7pm. The average diameter of the particles may be determined by dynamic light scattering (e.g. using a Zetasizer ZS90, Malvern Instruments, UK).

[0119] The additive may have a conductivity of 0.1 Scm1or more, such as 1 Scm1or more, preferably 10 Scm1or more, such as 100 Scm1or more, or IkScm1or more. The conductivity of the additive may be lOOMScm1or less, such as 63MScm-1or less, for example lOMScm1or less, such as IMScm1or less. The conductivity of the additive may be from 0.1 Scm1to lOOMScnrL, such as from 10 Scm1to 63M Scm1.

[0120] The additive may have a surface area of 10,000 m2 / g or less, such as 5,000 m2 / g or less, or 2,000 m2 / g or less, such as 1200m2 / g or less. The surface area of the additive may be 0. 1 m2 / g or more, such as 0.5 m2 / g or more, or 1 m2 / g or more, preferably 5 m2 / g or more, or 10 m2 / g or more, such as 100 m2 / g or more, or 200 m2 / g or more, or 500 m2 / g or more. The surface area of the additive may be from 0.1 to 10,000m2 / g, such as from 10 to 10,000m2 / g, or from 100 to 10,000m2 / g. The surface area of the particles may be determined using Brauner, Emmett and Teller (BET) analysis.

[0121] Combinations

[0122] In some embodiments: the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), thermoplastic polyimide (TPI), polyvinylidene fluoride (PVDF), or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is present in an amount of from 1% to 95% (e.g. from 8% to 92%) by weight (in one embodiment the polymer may also be selected from the list consisting of polyaryletherketone (PAEK), polyphenyl sulfone (PPSU), and fluorinated ethylene propylene (FEP)), or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, PEEK, PEKK, PPS, PEI, TPI, PVDF, or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is present in an amount of from 1% to 95% (e.g. from 8% to 92%) by weight, and the particles of the additive have an average diameter of from lOnm to 40pm (e.g. from lOnm to 10pm) (in one embodiment the polymer may also be selected from the list consisting of PAEK, PPSU, and FEP), or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, PEEK, PEKK, PPS, PEI, TPI, PVDF, or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is present in an amount of from 1% to 95% (e.g. from 8% to 92%) by weight, and the additive has a surface area of lm2 / g or more (e.g. from 1 to 10,000 m2 / g) (in one embodiment the polymer may also be selected from the list consisting of PAEK, PPSU, and FEP), or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, PEEK, PEKK, PPS, PEI, TPI, PVDF, or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is a conductive form of carbon (e.g. amorphous carbon, graphite or graphene), and the additive is present in an amount of from 25% to 99% (e.g. from 60% to 95%) by weight (in one embodiment the polymer may also be selected from the list consisting of PAEK, PPSU, and FEP), or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, PEEK, PEKK, PAEK, PPS, PPSU, PEI, TPI, PVDF, FEP, or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is selected from electrically conductive forms of carbon (e.g. selected from glassy carbon (GC) powder, graphene nanoplatelets (GnP) powder, and carbon black (CB)) and / or a metal (e.g. selected from the list consisting of: Ag, Au, Fe, Zn, Pt, Ni, Al, Bi, Sn, Sb, Pb, Ag, In, Cu and Cr, and alloys thereof), and the additive is present in an amount of from 25% to 99% (e.g. from 60% to 95%) by weight, or the polymer is selected from the list consisting of PEEK, PEKK, PAEK, PPS, PPSU, PEI, TPI, PVDF, FEP, or polypropylene, and the additive is selected from electrically conductive forms of carbon (e.g. selected from glassy carbon (GC) powder, graphene nanoplatelets (GnP) powder, and carbon black (CB)) and a metal (e.g. selected from the list consisting of: Ag, Au, Fe, Zn, Pt, Ni, Al, Bi, Sn, Sb, Pb, Ag, In, Cu and Cr, and alloys thereof), and the additive is present in an amount of from 25% to 99% (e.g. from 60% to 95%) by weight, or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, PEEK, PEKK, PAEK, PPS, PPSU, PEI, TPI, PVDF, FEP, or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is a combination of two or more conductive form of carbon (e.g. amorphous carbon, graphite or graphene), and the additive is present in an amount of from 25% to 99% (e.g. from 60% to 95%) by weight, or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, PEEK, PEKK, PAEK, PPS, PPSU, PEI, TPI, PVDF, FEP, or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is a mixture of two or more metals (e.g. selected from the list consisting of: Ag, Au, Fe, Zn, Pt, Ni, Al, Bi, Sn, Sb, Pb, Ag, In, Cu and Cr, and alloys thereof), and the additive is present in an amount of from 20% to 98% (e.g. from 40% to 90%) by weight, or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, PEEK, PEKK, PPS, PEI, TPI, PVDF, or a copolymer thereof (preferably selected from polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof), and the additive is a metal (e.g. selected from the list consisting of: Ag, Au, Fe, Zn, Pt, Ni, Al, Bi, Sn, Sb, Pb, Ag, In, Cu and Cr, and alloys thereof), and the additive is present in an amount of from 20% to 98% (e g. from 40% to 90%) by weight (in one embodiment the polymer may also be selected from the list consisting of PAEK, PPSU, and FEP), or the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof, and the additive is present in an amount of from 1% to 95% (e.g. from 8% to 92%) by weight, and the particles of the additive have an average diameter of from lOnm to 40pm (e.g. from lOnm to 10pm), and the additive is selected from the list consisting of: amorphous carbon (e.g. carbon black), graphite, graphene (e g. graphene nanoplates), Ag and Ni.

[0123] Production of

[0124] The second aspect provides a method for producing a composite, wherein the composite is for electrochemical apparatus. The method comprises: providing a polymer selected from the list consisting of poly(halo)olefin, poly(thio)ether and polyimide, providing a particulate additive, wherein the additive comprises an electrically conductive form of carbon, a metal or a mixture thereof, combining the polymer with the particulate additive to provide a composite precursor, and heating the composite precursor to melt the composite precursor and form the composite.

[0125] The step of combining the polymer with the particulate additive to provide a composite precursor may comprise mixing the solid polymer with the particulate additive. This is particularly suitable for polymers that are poorly soluble in organic solvents.

[0126] Preferably the step of combining the polymer with the particulate additive comprises dissolving the polymer in an organic solvent to form a solution of the polymer in the organic solvent, dispersing the particulate additive in the solution so as to provide a dispersion, and cooling the dispersion and / or adding an anti-solvent to the dispersion to precipitate the composite precursor. The method may comprise separating (e.g. by filtration) the composite precursor from the organic solvent and any anti-solvent.

[0127] The organic solvent may be selected from the list consisting of: acetone, benzene, chlorobenzene, chloroform, cyclohexane, decalin, 1,2-dichloroethane, diethyl ether, diglyme (diethylene glycol dimethyl ether), glyme (1,2-dimethoxyethane), dimethylformamide, dimethyl sulfoxide, 1,4- dioxane, ethyl acetate, heptane, hexane, methyl t-butyl ether, methylene chloride, nitromethane, pentane, petroleum ether (ligroin), pyridine, tetrahydrofuran, tetralin, toluene, triethylamine, and xylene. Preferably the organic solvent is apolar. Preferably, especially where the polymer is a poly(halo)olefin, the organic solvent is selected from the list consisting of benzene, decalin, tetralin, toluene and xylene. More preferably the organic solvent is selected from toluene and xylene.

[0128] The skilled person will appreciate that the amount of solvent used should allow the polymer to be dissolved at some temperature. The amount of the solvent, relative to the amount of polymer, may be 100% or more by weight, such as 200% or more, or 500% or more, or 800% or more relative to the amount of polymer by weight. The amount of solvent, relative to the amount of polymer, may be 10,000% or less, such as 5,000% or less, or 2,000% or less, such as 1,000% or less by weight. The amount of solvent, relative to the amount of polymer, may be from 100% to 10,000% by weight, such as from 500% to 2,000% by weight.

[0129] Dissolving the poly(halo)olefin may involve heating the organic solvent to a temperature of 60°C or more, such as 90°C or more, or 120°C or more, such as 130°C or more. The temperature may be 200°C or less, such as 150°C or less, for example 140°C or less. The temperature may be from 60 to 200°C, such as from 120 to 150°C. The organic solvent may be heated to its boiling point, for example under reflux. The temperature may depend on the solvent used. The poly(halo)olefin may be dissolved in the organic solvent prior to adding the additive. Preferably the additive may be dispersed in the organic solvent prior to adding the poly(halo)olefin.

[0130] The relative amounts of the poly(halo)olefin and the additive may be as defined in relation to the composite.

[0131] Preferably the additive and the poly(halo)olefin are homogenously dispersed throughout the organic solvent. This helps to provide a uniform composite that can achieve robust printability and uniform conductivity. The organic solvent and the poly(halo)olefin and / or additive may be agitated, for example by stirring and / or sonication.

[0132] The dispersion may be cooled to a temperature of 10°C or more lower than the temperature to which the organic solvent was heated when dissolving the poly(halo)olefin, for example 20°C or more lower, or 50°C or more lower, or 100°C or more lower. The temperature to which the dispersion is cooled may be from 10°C to 200°C lower than the temperature to which the organic solvent was heated when dissolving the poly(halo)olefin, such as from 50°C to 150°C.

[0133] The dispersion may be cooled to a temperature of 50°C or lower (e.g. from 0°C to 50°C), such as 40°C or lower, or 30°C or lower, for instance 20°C or lower.

[0134] The anti-solvent may be a polar and / or protic organic solvent. The anti-solvent may be a solvent selected from the list consisting of alcohols (e.g. methanol, ethanol, propanol (e.g. isopropanol), and butanol), acetonitrile, dimethylformamide, dimethyl sulfoxide, cyclohexane, 1,2- dichloroethane, diethyl ether, diglyme (diethylene glycol dimethyl ether), glyme (1,2- dimethoxyethane), 1,4-dioxane, ethyl acetate, heptane, hexane, methyl t-butyl ether, methylene chloride, nitromethane, pentane, petroleum ether (ligroin), pyridine, tetrahydrofuran, and triethylamine. Preferably, the anti-solvent may be selected from alcohols, acetonitrile, dimethylformamide, dimethyl sulfoxide, diethyl ether, glyme, diglyme, 1,4-dioxane, methyl t- butyl ether, nitromethane, pyridine, tetrahydrofuran, and triethylamine, Preferably the antisolvent is an alcohol, especially ethanol.

[0135] The volume of antisolvent, relative to the volume of solvent, may be 10% or more, such as 50% or more, or 100% or more, such as 200% or more. The volume of antisolvent, relative to the volume of solvent, may be 1000% or less, such as 500% or less, or 300% or less. The volume of antisolvent, relative to the volume of solvent, may be from 10% to 1000%, such as from 50% to 500%.

[0136] The antisolvent selected and the amount thereof may depend on the poly(halo)olefin and the organic solvent. The skilled person will readily be able to determine whether or not a particular solvent acts as an antisolvent for a given poly(halo)olefin and a given organic solvent.

[0137] The solution may be cooled prior to addition of an antisolvent. The antisolvent may be added to the solution prior to cooling. The solution may be cooled simultaneously to the addition of an antisolvent.

[0138] The dispersion may be agitated, for example sonicated and / or stirred, during and / or after the cooling and / or the addition of the antisolvent. Agitation may enhance the rate of precipitation of the composite precursor.

[0139] The composite precursor, comprising the additive and the poly(halo)olefin, may be isolated by evaporation, filtration and / or centrifugation to remove the organic solvent (and any anti-solvent).

[0140] In the composite precursor, the additive may be effectively trapped within a matrix of the poly(halo)olefin. The composite precursor typically has a porous structure that is not suitable for 3D printing.

[0141] Heating and melting the composite precursor destroys its porous structure of the composite precursor, providing a non-porous composite that is suitable for 3D printing. The composite precursor is heated to a temperature of at least the melting point of the poly(halo)olefin, for example 2°C or more above, or 10°C or more, such as 30°C or more above the melting point of the poly(halo)olefin. The composite precursor may be heated to a temperature of from 2°C to 100°C above the melting point of the poly(halo)olefin, such as from 2°C to 50°C. The temperature to which the composite precursor is heated may be from 150°C to 300°C, such as from 180°C to 260°C. For metal-based composite precursors, the mixing may be carried out at a temperature of about 190°C (e.g. 180 to 200°C), while the carbon-based composite precursors may require a higher temperature of about 250°C (e.g. 240-260°C).

[0142] The composite precursor and / or composite may be extruded. The composite precursor may be simultaneously heated and extruded to provide the composite. Extrusion of the composite or the composite precursor may provide the composite as a filament for 3D printing. The composite precursor and / or composite may be extruded through an extrusion die. The aperture of the extrusion die may be substantially circular in cross-section. The aperture of the extrusion die may have a diameter of 0.5mm or more, such as 1.0mm or more, or 1 ,5mm or more. The diameter may be 10mm or less, such as 5mm or less, or 2.0mm or less. The diameter may be from 0.5mm to 10mm, such as from 1.5mm to 2.0mm.

[0143] The composite precursor and / or composite may be extruded using a twin-screw extruder, such as a Thermo Scientific HAAKE minilab II. The composite precursor and / or composite may be extruded one or more times, such as two or three or more times.

[0144] Preferably the composite of the first aspect is obtainable (e.g. obtained) by the process of the second aspect.

[0145] Articles and Apparatuses

[0146] The third aspect provides an article comprising the composite of the first aspect.

[0147] Where the article is an electrode, the article may have an elongate cuboidal shape or an elongate cylindrical shape, for example having a length that is 5 or more (e.g. 10 or more) times greater than its width or depth.

[0148] The fourth aspect provides an electrochemical screening apparatus. Each electrode of the apparatus of the fourth aspect may be made of the composite of the first aspect.

[0149] The pairs of electrodes may be electrically connected in series (whereby one electrode of one pair is electrically connected to one electrode of another pair) and / or in parallel (whereby the two electrodes of one pair are individually electrically connected to the two electrodes of another pair). Each electrode may be removable from the head to which it is attached, for example to facilitate replacement of the electrodes.

[0150] The apparatus may have two or more terminals, wherein each terminal is for electrically connecting a power source to one or more electrodes.

[0151] In one embodiment, the electrode mountings comprise a plurality of physically connected heads.

[0152] The electrodes may be elongate electrodes extending from each physically connected head. The electrochemical screening apparatus may comprise a base, wherein the base comprises a plurality of chemically and electrically isolated wells, wherein the wells are configured to each simultaneously receive a pair of the elongate electrodes. The electrochemical screening apparatus may be configured to seal between each head and each corresponding well. Each head may comprise a fluid (e.g. gas) connector to facilitate fluid (e.g. gaseous) communication to the corresponding well. Each head may be fluidly connected to another head, for example to allow the passage of gases (such as inert gases) between the reactor wells. Each well may be substantially cylindrical in shape.

[0153] It will be understood that the base and most of the head are typically an electrically isolating material. The electrically isolating material may be a polymer (including conventional polymers for 3D printing, such as PLA, ABS, and TPU), such as a poly(halo)olefin, especially polypropylene. Electrically conductive portions of the head may be used to electrically connect the electrodes to one another and / or the terminals. Such electrically conductive portions may comprise the composite of the first aspect.

[0154] As discussed above, the cavities may be wells. Thus, the body may be a well plate. The electrodes may be situated within each well of the well plate. The electrodes may extend from one or more sides (or the base) of each cavity (e.g. well), or the electrodes may form (part or all of) one or more sides (or the base) of each cavity (e.g. well).

[0155] The screening apparatus may comprise heads that are able to form a seal with the cavities. Each head may comprise a fluid (e.g. gas) connector to facilitate fluid (e g. gaseous) communication to the corresponding cavity (e.g. well). Each cavity (e g. well) may be substantially cylindrical in shape.

[0156] It will be understood that sections of the body that are not the electrodes are typically electrically isolating. Electrically isolating sections of the body may be made of a polymer selected from the list consisting of poly(halo)olefin, poly(thio)ether and polyimide without any particulate additive as required for the claimed invention. Electrically conductive portions of the cavity may be used to electrically connect the electrodes to one another and / or the terminals. Such electrically conductive portions may comprise the composite of the first aspect.

[0157] The fifth aspect provides an electrochemical apparatus comprising a head, a body, and a pair of elongate electrodes, wherein the body is able to rotate about an axis relative to the head, and wherein the body and the head are secured to one another. The apparatus of the fifth aspect may be configured such that the electrodes of the pair of electrodes can contra-rotate or corotate relative to one another. The apparatus of the fifth aspect may be configured such that one electrode of the pair of electrodes does not rotate while the other electrode rotates. The direction of rotation of each electrode may be alternated between clockwise and anticlockwise.

[0158] Where the apparatus of the fifth aspect is configured such that the first and second electrodes are able to co-rotate, i.e., rotate about an axis in the same direction, the direction of rotation may be changed. For example, the direction of rotation of the corotating first and second electrodes may be changed from clockwise rotation to anticlockwise rotation, or may be changed from anticlockwise rotation to clockwise rotation.

[0159] Where the apparatus of the fifth aspect is configured such that the first and second electrodes are able to contra-rotate, i.e., rotate about an axis in opposite directions to one another, the direction of rotation of the contrarotating first and second electrodes may be changed. For example, the direction of rotation of the first electrode may be changed from clockwise rotation to anticlockwise rotation and the direction of rotation of the second electrode may be changed from anticlockwise rotation to clockwise rotation, or the direction of rotation of the first electrode may be changed from anticlockwise rotation to clockwise rotation and the direction of rotation of the second electrode may be changed from clockwise rotation to anticlockwise rotation.

[0160] Where the apparatus of the fifth aspect is configured such that one electrode of the pair of electrodes does not rotate while the other electrode rotates, the direction of the rotating electrode may be changed. For example, the direction of rotation of the rotating electrode may be changed from clockwise rotation to anticlockwise rotation, or may be changed from anticlockwise rotation to clockwise rotation.

[0161] The direction of rotation may be changed (e g reversed) regularly, for example every 10 seconds or less, such as every 2 seconds or less, or every 1 second or less, for example every 0.5 seconds or less, or every 0.3 seconds or less. The direction of rotation may be changed at an interval of every 0.001s or more, such as every 0.01 s or more, or every 0.1s or more. The direction of rotation may be changed (e.g. reversed) every 0.001 to 10s, such as every 0.01 to 2 seconds.

[0162] The body may comprise an elongate shaft. The shaft may be a hollow shaft to act as a conduit for cables to electrically connect the electrodes to a power supply. The head may comprise an attachment to the elongate shaft of the body. The head may comprise a motor configured to rotate the body (e g. via the elongate shaft) relative to the head. The apparatus (e g. the shaft) may comprise a slip ring connector for the electrical connection to one or more of the electrodes, to allow the electrical connection to be maintained during rotation of the body relative to the head.

[0163] It will be understood that the terminals are electrically isolated from one another.

[0164] The electrochemical apparatus may comprise n electrodes. When n is three or more, from 2 to n-1 of the electrodes may be electrically connected to one another, for example by a connecting portion in the body and / or head.

[0165] Each electrode of the apparatus of the fifth aspect may be made of the composite of the first aspect. Each electrode may be removable from the body of the apparatus of the fifth aspect, for example to facilitate replacement of the electrodes.

[0166] The base may have a cross-sectional shape (in a plane perpendicular to the axis of rotation) that is a circle, an ellipse, a triangle, a square, or an n-sided polygon, wherein n is selected from 5 to 12. Preferably, the cross-section is circular.

[0167] It will be understood that most of the base and most of the head is typically an electrically isolating material. The electrically isolating material may be a polymer (including conventional polymers for 3D printing, such as PLA, ABS, and TPU), such as a poly(halo)olefin, especially polypropylene. Electrically conductive portions of the base may be used to electrically connect the electrodes to the terminals in the head. Such electrically conductive portions may comprise the composite of the first aspect.

[0168] The seventh aspect provides an electrochemical flow cell. Where the electrically isolating material transmits ultraviolet (UV), visible and / or infrared radiation, electrochemical reactor may be termed a photoelectrochemical flow cell. For example, the electrically isolating material may be polypropylene. This may enable a reaction to be performed and / or monitored such radiation.

[0169] The photoelectrochemical flow cell may comprise a light source, for example a UV, visible and / or infrared light source.

[0170] The flow cell may comprise a plurality of modules. The modules may be stacked as levels. Each level comprises a fluid inlet and a fluid outlet, and the apparatus is configured such that the fluid emanating from the outlet of one level is transmitted to the fluid inlet of another level. In other words, the fluid outlet of one level may be fluidly connected to the fluid inlet of another level.

[0171] The flow cell may comprise a temperature control fluid channel to heat and / or cool fluid passing through the conduit. The temperature control fluid channel should be fluidly isolated from the conduit. The temperature control fluid channel may be defined by a separate level or sheet. The temperature control fluid channel may be directly above and below the conduit. The temperature control fluid may be water.

[0172] The flow cell may comprise more than one electrochemical flow cells, such as two electrochemical flow cells. The more than one electrochemical flow cell, such as two electrochemical flow cells, may be stacked on top of each other. The spatial polarity of the electrodes in the upper electrochemical flow cell is the opposite of the spatial polarity of the electrodes in the lower electrochemical flow cell, i.e ., the spatial polarity of the electrodes in the upper electrochemical flow cell was reversed. Such a flow cell may be termed a pseudo alternating polarity flow cell.

[0173] Preferably the electrodes of the electrochemical flow cell of the sixth aspect may each be independently made of the composite of the first aspect.

[0174] Clauses

[0175] 1. A 3D-printable composite for an electrochemical apparatus, wherein the composite comprises: a polymer selected from the list consisting of polyolefin, poly(thio)ether and polyimide, and a particulate additive, wherein the additive comprises an electrically conductive form of carbon, a metal or a mixture thereof.

[0176] 2. The composite of clause 1, wherein the polymer is selected from the list consisting of: polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, polyetherimide, thermoplastic polyimide, polyvinylidene fluoride, and polypropylene.

[0177] 3. The composite of clause 2, wherein the polyolefin is polypropylene.

[0178] 4. The composite of any preceding clause, wherein the particles of the additive have an average diameter of from lOnm to 40pm.

[0179] 5. The composite of any preceding clause, wherein the additive has a surface area of lm2 / g or more.

[0180] 6. The composite of any preceding clause, wherein the particulate additive is selected from the list consisting of: glassy carbon, graphene, and amorphous carbon.

[0181] 7. The composite of clause 6, wherein the particulate additive comprises a mixture of amorphous carbon and graphene. 8. The composite of any preceding clause, wherein the metal is selected from the list consisting of Ag, Fe, Cr and Ni, and alloys thereof.

[0182] 9. The composite of clause 8, wherein the metal is nickel.

[0183] 10. The composite clause 1, wherein: the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof, the particles of the additive have an average diameter of from lOnm to 40pm, and the additive is selected from the list consisting of: amorphous carbon, graphite, graphene, Ag and Ni.

[0184] 11. An article comprising the composite of any one of clauses 1 to 10.

[0185] 12. The article of clause 11, wherein the article is an electrochemical apparatus, an electrochemical reactor, an electrode, a sensor, battery, or a fuel cell.

[0186] 13. A method for producing a composite, wherein the composite is for electrochemical apparatus, wherein the method comprises: providing a polymer selected from the list consisting of polyolefin, poly(thio)ether and polyimide, providing a particulate additive, wherein the additive comprises an electrically conductive form of carbon, a metal or a mixture thereof, combining the polymer with the particulate additive to provide a composite precursor, and heating the composite precursor to melt the composite precursor and form the composite.

[0187] 14. The method of clause 13, wherein the step of combining the polymer with the particulate additive comprises: dissolving the polymer in an organic solvent to form a solution of the polymer in the organic solvent, dispersing the particulate additive in the solution so as to provide a dispersion, and cooling the dispersion and / or adding an anti-solvent to the dispersion to precipitate the composite precursor.

[0188] 15. The method of clause 13, wherein the step of combining the polymer with the particulate additive to provide a composite precursor comprises mixing the solid polymer with the particulate additive.

[0189] 16. An electrochemical screening apparatus for simultaneously screening a plurality of electrochemical reactions, wherein the electrochemical screening apparatus comprises: a plurality of physically connected heads and a plurality of pairs of elongate electrodes, wherein one pair of the pairs of elongate electrodes extends from each head, wherein the elongate electrodes extend in the same direction as one another, wherein the electrodes of each pair are electrically isolated from one another, and wherein at least one electrode of each pair is electrically connected to at least one electrode of another pair.

[0190] 17. An electrochemical apparatus comprising: a head, a body, and a pair of elongate electrodes, and wherein: the body is able to rotate about an axis relative to the head, the body and the head are secured to one another, one or both of the pair of electrodes is or are configured to rotate with the body, the electrodes extend in substantially the same direction as one another, the direction in which the electrodes extend is substantially parallel with the axis of rotation, and the electrodes are electrically isolated from one another. 18. The apparatus of the clause 17, wherein the apparatus comprises: a first body, a second body, a first electrode of the pair of electrodes, and a second electrode of the pair of electrodes; wherein the first body is attached to or unitary with the first electrode, and the second body attached or unitary with the second electrode, and wherein the apparatus is configured such that the first electrode and / or the second electrode can rotate about an axis.

[0191] 19. A method of operating an electrochemical apparatus comprising a pair of electrodes, wherein one or both of the electrodes is or are configured to move, wherein the method comprises, whilst the electrodes are in contact with a reaction medium, and whilst a potential difference is applied across the electrodes, moving one or both of the electrodes through the reaction mixture in a first direction, and moving the one or both of the electrodes through the reaction mixture in a second direction.

[0192] 20. The method of clause 1 , wherein one or both of the electrodes are specifically configured to rotate such that they move through the reaction medium, and the first direction and the second direction correspond to clockwise rotation and anticlockwise rotation.

[0193] 21. An electrochemical apparatus comprising a flow cell, wherein the flow cell comprises: a fluid inlet, a fluid outlet, and two sheets of electrically isolating material, wherein the two sheets of electrically isolating material are spaced apart by a pair of electrodes, wherein the electrodes are interdigitated with one another, wherein the electrodes are electrically isolated from one another, and wherein a void between the interdigitations of the electrodes defines a conduit that allows fluid to pass from the fluid inlet to the fluid outlet.

[0194] 22. The electrochemical apparatus of clause 21, wherein the electrically isolating material transmits ultraviolet, visible and / or infrared radiation.

[0195] 23. The electrochemical apparatus of clause 21 or clause 22, wherein one or both of the sheets of electrically isolating material comprise one or more conduits for temperature control fluid.

[0196] 24. The electrochemical apparatus of any one of clauses 21 to 23, wherein the apparatus comprises two or more flow cells fluidly connected in series, and configured such that the polarity of the electrodes of two adjacent flow cells is alternated with respect to one another.

[0197] 25. The electrochemical screening apparatus, the electrochemical apparatus, the method, or the electrochemical flow cell of any one of clauses 16 to 24, wherein the electrodes are each independently made of the composite of any one of clauses 1 to 10.

[0198] Examples

[0199] Materials

[0200] The following materials were used as additives: polypropylene (RS PRO 1.75mm Transparent PP 3D Printer Filament), glassy carbon (glassy carbon spherical powder, 0.4-12 micron, type 1, Thermo Scientific Chemicals), graphene nanoplatelets (xGnP® Graphene Nanoplatelets - Grade M 120 - 150 m2 / g, XG Sciences), and carbon black (PRINTEX® XE2-B, Orion Engineered Carbons).

[0201] Example la: Hybrid mixing to manufacture composite filament.

[0202] Figure 1 of the accompanying drawings shows a flowchart illustrating an example of the hybrid mixing methodology used to prepare the composite of the present invention. It will be appreciated that alterations to the polymer and additive, and the amounts thereof, is within the skill of the user based on the following general protocol.

[0203] The additive is dispersed in a suitable organic solvent (e.g. xylene) by stirring for 30 minutes. Poly(halo)olefin (e g. polypropylene) is added to the dispersion of additive in the organic solvent, and the resulting mixture is heated (e.g. under reflux, 140°C for xylene) until dissolution of the poly(halo)olefin. For polypropylene and xylene, the mass of xylene was ten times the mass of polypropylene. The same volume of cold antisolvent (e.g. 0°C ethanol) as the amount of xylene was added to the suspension of additive in the solution of polypropylene in xylene to precipitate the composite precursor, which had a porous structure. The composite precursor was extruded at 190-250°C and 60rpm using a Haake twin-screw extruder to provide the composite.

[0204] The composite was processed into a filament using as Filafab extruder and a filament spooler. Due to the high melt viscosity of carbon-based additive containing composites, high processing temperatures (220-250 °C) were required to attain adequate flowability. In contrast, the metalbased additive containing composites required lower processing temperatures of about 190°C as they were prone to stretching during extrusion due to the high density of these composites.

[0205] Figure 2 of the accompanying drawings shows a FilaFab filament extruder (A) paired with the hybrid mixing method, and spool winder (B).

[0206] The solution mixing process was seamlessly scaled up to handle greater than 100 grams of material, implying its viability for large-scale production. The dried composites were subsequently subjected to three rounds of melt mixing, and the resulting composite was used to prepare substantial quantities of filament.

[0207] Example lb: Hotplate mixing to manufacture composite filament

[0208] Composites were prepared by mixing polymer powder with a predetermined weight loading of conductive additives. An initial additive loading of 20 wt% was tested. If a homogeneous composite could not be processed, the loading was reduced in 5 wt% increments until a uniform composite was achieved. The conductive additives tested included graphene nanoplatelets and carbon black in a 1: 1 ratio by weight. To melt process these composites, a high-temperature hotplate was preheated to the required processing temperature for the selected polymer. The polymer and conductive additives were then introduced onto hotplate and melt-mixed using a metal spatula. The resulting composite was manually processed into a filament for further characterisation.

[0209] Hotplate mixing is suitable for the manufacture of a composite filament on a small scale, and produces a composite similar to that produced by the hybrid mixing method described in Example la. However, hotplate mixing is not capable of large scale application or commercially viable.

[0210] The following composite filaments were manufactured using the above method.

[0211] Example 2a: Solvent Resistance Testing - compositions of the invention

[0212] THF and DCM been established as incompatible organic solvents with PP, causing significant swelling of PP over time.

[0213] A composite was prepared containing polypropylene, ECB and GnP in a weight ratio of 70: 15: 15. The composite and pristine polypropylene (PP) were immersed in methylene chloride (DCM) and tetrahydrofuran (THF) for three weeks. The change in mass of the composite and of the pristine polypropylene were measured before and after the exposure.

[0214] Figure 3 of the accompanying drawings shows the results of this study.

[0215] Surprisingly, the composite gained significantly less mass compared to the pristine polypropylene. For each of THF and DCM, the mass change was approximately halved for the composite compared to the pristine polypropylene. Without being bound by theory, the increased solvent resistance of the composite may be attributed to several factors. Firstly, the addition of the additive reduces the quantity of swellable polypropylene in the composite. Additionally, the improved barrier properties of GnPs may reduce the rate of solvent penetration into the composite. Further, the inclusion of ECB increased the viscosity of the composite, also potentially increasing the resistance of the composite to swelling.

[0216] The solvent resistance of composites was also assessed by measuring the resistance of the composite over 170 hours.

[0217] A composite containing polypropylene, graphite nanoparticles and extra-conductive carbon black (PP 70wt%, GnP 15wt%, ECB 15wt%) was found to be compatible with the solvents DMF, DMA, DMSO, HFIP, ethanol, methanol, acetonitrile, methylene chloride, THF, diethyl ether and ethyl acetate.

[0218] A composite containing polypropylene and nickel (85wt% Ni, 15wt% PP) was found to be compatible with the solvents DMF, DMA, DMSO, HFIP, ethanol, methanol, and acetonitrile.

[0219] Therefore, the composites display surprising resistance to an array of common organic solvents.

[0220] The composite filament manufactured using hotplate mixing was subjected to solvent resistance testing. Equal-length samples were cut from the composite filaments, and their initial weights were recorded. These samples were then submerged in sealed vials filled with the solvents under investigation. After 6 hours, samples were extracted with tweezers, the excess solvent was removed with a paper towel, and the dry samples were weighed to identify any change in mass.

[0221] The results of this testing are shown in Figure 4 of the accompanying drawings. Bars are shown to illustrate the change in mass of each sample in each solvent over the course of the experiment. “X” illustrates a negative 100% bar, and “O” is used to emphasise results where no significant change was observed. All polymers showed less than 10% mass change in at least two of the solvents tested. PEEK, PPS, and FEP composites showed high resistance to MeOH, MeCN, DCM, or DMF. The PEKK composite showed high resistance to MeOH, MeCN, or DMF, and reasonable resistance to DCM. PPSU and TPI composites showed high resistance to MeOH or MeCN. The PEI composite showed high resistance to MeOH, MeCN and DMF. The PAI composite showed high resistance to MeOH, MeCN or DMF. Therefore, to achieve resistance to MeOH or MeCN, any of PEEK, PEKK, PPS, PPSU, TPI, PEI, PAI and / or FEP may be chosen. To achieve resistance to DCM, any of PEEK, PEKK, PPS and / or FEP can be chosen. To achieve resistance to DMF, any of PEEK, PEKK, PPS, PEI, PAI and / or FEP can be chosen.

[0222] Example 2b: Solvent Resistance Testing - comparative compositions

[0223] Conventional polymers PVA, PET, PLA, conductive PLA and conductive PVDF (sold under the brand name add orth™) were examined to determine solvent resistance. Equal-length samples were cut from the polymer, and their initial weights were recorded. These samples were then submerged in sealed vials filled with the solvents under investigation. After 6 hours, samples were extracted with tweezers, the excess solvent was removed with a paper towel, and the dry samples were weighed to identify any change in mass.

[0224] The results of this study are shown in Figure 5 of the accompanying drawings. PVA readily dissolved in water, which was confirmed through additional testing. Given that water is often used in electrosynthesis, PVA is unsuitable for 3D-printable electrodes. While all other polymers and polymer composites remained stable in MeOH, moderate to severe swelling was observed in MeCN and DMF, with complete dissolution occurring in DCM.

[0225] Example 3a: Electrical Conductivity of Composites of the invention

[0226] Various composites of the invention were produced, and the conductivity of these composites was determined.

[0227] In one investigation, composites of polypropylene and a conductive carbon form based additive (ECB, GnP or GC) were prepared, with different weight percentages of the additive relative to the polypropylene. ECB composites were prepared containing 5-25 wt% ECB. GnP composites were prepared containing 10-35 wt% GnP. GC composites were prepared containing 50-60 wt% GC.

[0228] Figure 6 of the accompanying drawings shows the conductivity of the composites containing the conductive forms of carbon for each wt% loading. The composites were each significantly more conductive than pristine polypropylene. The conductivity of the composites each increased as the amount of the additive was increased.

[0229] ECB provided the highest conductivity, reaching about 3 Scm1at a loading of 25 wt%. GnP provided a conductivity of about 0.5 Scm1at 35 wt% loading. GC provided a conductivity of about 0.05 Scm1at 60 wt% loading. 1

[0230] Conversely, both the higher intrinsic conductivity and surface area (120-150 m2 / g) of GnPs likely resulted in the substantially lower percolation threshold of the corresponding composite. The increased porosity of stacked graphene platelets leads to the larger surface area.

[0231] Interestingly, while ECB demonstrates the lowest intrinsic conductivity of the carbon additives tested, the incredibly high surface area (1000 m2 / g) yielded a composite with the lowest percolation threshold and highest conductivity. These observations can be explained by the highly branched and complex structure of ECB maximising the formation of conductive pathways.

[0232] The relatively lower conductivity of GC may be due to its non-porous structure, resulting in the formation of minimal conductive pathways. This may be due to its low surface area of around 2 m2 / g.

[0233] In another investigation, composites of polypropylene (70 wt%), and ECB and GnP (total 30 wt%) were prepared with weight ratios of ECB and GnP from 7.5:22.5 to 22.5:7.5. The conductivity of these composites was determined.

[0234] Figure 7 of the accompanying drawings shows conductivity of PP(70 wt%)GnPECB(30 wt%) with different GnP:ECB wt. loading ratios. At a weight percentage of 30% GnPs, a conductivity of 0.68 Scm1was observed, while the same composition using ECB exceeded the saturation limit. All composites incorporating both GnP and ECB produced conductivities greater than 2 Scm1, with the highest (8 Scm2) surpassing all other compositions prepared. This enhanced conductivity corroborates the synergistic effects previously discussed.

[0235] Specifically, ECB particles likely serve as a connecting bridge between the large GnP sheets, reducing the percolation threshold and generating a denser conductive network. An increase in conductivity was observed with increasing ECB content which can be rationalised by the fact that ECB yields more conductive composites compared to GnP.

[0236] Figure 8 of the accompanying drawings shows the conductivity of polypropylene composites with metal additives (silver (Ag), stainless steel (SS) and nickel (Ni)) at various weight percentage loadings. As with the carbon composites, a direct correlation between percolation threshold and particle size (proportional to surface area) was observed. The composite comprising stainless steel particles provided higher conductivity than polypropylene alone. However, the stainless steel composite had limited observable percolation threshold and had relatively low conductivity. This behaviour may be attributed to a combination of the lower intrinsic conductivity of stainless steel and large relative particle size (44 pm), minimising the formation the formation of a continuous conductive network.

[0237] The composite comprising silver particles was the most conductive composite tested, and had the lowest percolation threshold. This observation is credited to the high intrinsic conductivity of silver and the smaller particle size (0.1-0.5 pm), resulting in the formation of a dense conductive network with high conductivity between the particles. While this initially seemed very promising, visible aggregation upon processing warranted further investigation into the dispersion.

[0238] The composite comprising nickel particles had good conductivity due to its moderate particle size (3-7 pm) and high intrinsic conductivity. The composite comprising nickel particles was a more stable dispersion with no visible aggregation compared to other composites

[0239] The conductivity of composites of the invention produced using hotplate mixing was determined.

[0240] Using a 4-point probe (Keithley 2400 SourceMeter), the filament's resistance was measured 3 times at a known probe separation. The average conductivity is provided as set out below. p = Resistivity in Wm

[0241] E = Voltage measured by the voltmeter in Volts w = Width of the sample bar measured in meters h = Height of the sample bar measured in meters

[0242] I = Current the ammeter measures flowing through the sample in amperes

[0243] I = Distance between the two points where the voltmeter wires make contact with the bar, measured in meters

[0244] Conductivity (o) may then be calculated as the inverse of resistivity (p): o = 1 / p

[0245] The electrical conductivity of composites manufactured using hotplate mixing is shown in Figure 9 of the accompanying drawings. Composites of PEEK, PEKK, PPS, PPSU, TPI, PEI, PAI, and FEP polymers were found to be conductive. The lower conductivity of FEP, PAI, and TPI suggests they may be better suited for low-power applications. However, particularly high conductivity was observed for composites of PEEK, PEKK, PPS, PPSU and PEI. Example 3b: Resistivity change of composites of the invention after solvent exposure

[0246] The resistivity change of composites of the invention after solvent exposure was examined. Equal-length samples were cut from the composite filaments prepared using hotplate mixing, and their initial resistances were recorded. These samples were then submerged in sealed vials filled with the solvents under investigation. After 6 hours, the samples were extracted with tweezers, the excess solvent was removed with a paper towel, and their resistance was measured, as set out in Example 3a, to identify any change in conductivity.

[0247] The results of this investigation are shown in Figure 10 of the accompanying drawings. After exposure of PEEK, PEKK, PPS and FEP composites to MeOH, MeCN, DCM or DMF, adequate conductivity was retained. After exposure of the PPSU composite to MeOH, adequate conductivity was retained. After exposure of the TPI composite to MeOH, and MeCN, adequate conductivity was retained. After exposure of PEI and PAI composites to MeOH, MeCN, and DMF, adequate conductivity was retained.

[0248] Therefore, to achieve resistance to MeOH, any of PEEK, PEKK, PPS, PPSU, TPI, PEI, PAI and / or FEP can be chosen. To achieve resistance to MeCN, any of PEEK, PEKK, PPS, TPI, PEI, PAI and / or FEP can be chosen. To achieve resistance to DCM, any of PEEK, PEKK, PPS and / or FEP can be chosen (preferably any of PEEK, PPS and / or FEP can be chosen). To achieve resistance to DMF, any of PEEK, PEKK, PPS, PEI, PAI and / or FEP can be chosen.

[0249] Example 3c: Resistivity change of comparative conductive filament after solvent exposure Resistivity change of comparative conductive filaments after solvent exposure was examined. The same methodology was used as described in Example 3b. The samples tested were conductive composites of PLA and PVDF (comparative).

[0250] The results of this investigation are shown in Figure 11 of the accompanying drawings. Commercially available conductive PLA exhibited moderate retention of conductivity when exposed to MeOH but suffered a severe reduction in MeCN and complete dissolution in DCM and DMF. Commercially available conductive PVDF showed a significant loss of conductivity in MeCN and DMF, with complete dissolution in DCM. While MeOH caused PVDF minimal swelling or dissolution, conductivity could not be measured, suggesting a complete loss of surface conductivity.

[0251] This demonstrates that PLA and PVDF composites comprising carbon-based additives are not suitable in electrochemical applications. Example 4: 3D-printed screening apparatus

[0252] A 3D printer was used to prepare an electrochemical screening apparatus using the composite of the invention for the electrodes and conductive connectors between the electrodes. Figure 12 of the accompanying drawings depicts computer aided design images of a cross-sectional view through three head units and corresponding electrodes (left-hand image); a perspective view of the three head units and corresponding electrodes (middle image); and a perspective view of the three groups of three head units and corresponding electrodes being inserted into three base units.

[0253] The apparatus has interconnected headspaces A to facilitate the supply of inert gas to all reactors from a single source; serial connection B of preconnected electrodes, which enable the electrolysis of all reactions using a single power source; electrodes C that are replaceable to facilitate rapid modification of electrode design, size, and separation; and rubber septa joint D, which enables the reactions to be performed under an inert atmosphere. The reactor has a modular design, as demonstrated by interconnectable bases E, which enables the seamless assembly of rows of reactors, creating a unified and expansive screening apparatus.

[0254] Figure 13 of the accompanying drawings shows a photograph of 3D printed electrochemical screening apparatus according to the invention. The photograph shows four units, each comprising three heads and six electrodes; and an assembled electrochemical screening apparatus where two bases are joined together, and two units of three heads are sealed to the base units, with the electrodes within the base.

[0255] The influence of electrode surface area and separation in synthesis of pyrazolidine-3, 5-diones was investigated using 3D printed screening apparatus. Pyrazolidine-3, 5-diones are prominent heterocyclic motifs found in both natural products and pharmaceuticals, making them highly attractive structures. The literature suggests that the reaction shown below conventionally provides a yield of 66%.

[0256] The screening apparatus was employed to rapidly identify the optimal electrode separation for this reaction. Each head of a three-head screening apparatus was adapted to hold the pair of electrodes at different distances from one another, specifically at 2, 4 and 6mm separation. The yield produced by each electrode is shown below.

[0257] The results revealed that the largest gap resulted in the highest yields, surpassing the literature- reported yield.

[0258] The impact of electrode surface area on the reaction yield was investigated using the screening apparatus. Electrodes of different surface area were fitted to the heads of the screening apparatus. The results of this investigation are shown in the table below.

[0259] It was found that the highest yields were obtained when using the largest anodes, while changes to the cathode surface area had little effect. Two of the results surpassed the literature-reported yield. Given that the reaction of interest takes place at the anode, i.e., it serves as the working electrode, it is plausible that this contributes to the observed sensitivity. Additionally, varying electrode surface area is a reliable approach to investigate the impact of current density, a well- established factor affecting electrochemical reactions. Due to the intramolecular nature of this reaction, the use of larger anodes may effectively suppress any intermolecular reactions by reducing the current densities.

[0260] Thus, the screening apparatus of the invention proved highly valuable in studying the impact of electrode surface area and separation for the synthesis of pyrazolidin-3, 5 -diones.

[0261] Figure 14 of the accompanying drawings depicts an alternative electrochemical screening apparatus of the fourth aspect. The apparatus includes a body in which 96 wells are located. Part of the wall of well is made up of two electrodes that, in use, a potential difference can be applied across such that an electrolyte in each well is subjected to the potential difference. Other than the electrodes, the body is made of electrically insulating material. The apparatus is designed with the standard dimensions of a 96 well plate, although the standard dimensions of other well plates can be used, providing a high throughput electrochemical screening apparatus that can seamlessly integrate into existing automated liquid handlers and / or automated synthesis setups.

[0262] Example 5: 3D printed rotatable electrochemical apparatus

[0263] Figure 15 of the accompanying drawings shows an image (left) and computer aided design images (right) of a rotatable electrochemical apparatus according to the invention. The apparatus comprises 3D printed electrodes A, which are sized to fit into a standard Schlenk tube, allowing a reaction to be performed under an inert gas. The apparatus comprises a head unit B that is 3D- printed and securely holds the electrodes and that is rotatably attached to a rotating shaft (not shown) that has a conduit for electrical cables. The apparatus comprises a motor and a motor housing C, where motor housing C comprises a stopper to secure the motor to rotating shaft and seal the Schlenk tube. The apparatus comprises electrical connector D to connect the electrodes to a power supply through a slip ring mechanism.

[0264] The electrodes and base are shown in more detail by the CAD images on the right hand side of Figure 15. The apparatus comprises rotatable base E, which is 3D printed from electrically insulating polypropylene to prevent a short-circuit between the electrodes. The apparatus comprises 3D printed electrodes G (of the composite of the first aspect) arranged in a concentric ring pattern, wherein each electrode ring is of the opposite polarity to the two adjacent electrode rings such that the polarity of the electrodes alternates. Each electrode ring is comprised of a plurality of sub-electrodes. The rings of sub-electrodes provide increased convection between the electrodes when rotated. The sub-electrodes of each ring are joined by ring supports F to increase the rigidity and durability of the electrodes. The apparatus comprises 3D printed electrical connectors (of the composite of the first aspect) between the electrode rings to reduce the number of connections required to the base unit.

[0265] Figure 16 of the accompanying drawings shows the 3D-printed bodies and elongate electrodes of five rotatable apparatuses, and one fully assembled 3D-printed rotatable apparatus sealed in a Schlenk tube. Figure 17 of the accompanying drawings shows two alternative configurations of the 3D printed rotatable electrochemical apparatus. Yield was determined by19F NMR.

[0266] The 3D printed rotatable apparatus shown in Figures 15 and 16 was used to perform the same reaction as was performed in the screening apparatus. The apparatus was tested with the electrodes rotating in a continuous direction and was tested with the electrodes rotating in alternating directions (i.e. clockwise for two rotations, then anticlockwise for two rotations, then repeat). For comparative purposes, the yield obtained by the electrodes when stationary was 34%. When the reaction mixture was stirred using a stirrer bar, the yield was 70%. For both of these comparative examples, the current used was 5 mA.

[0267] The electrodes were set to rotate at 150rpm. When the apparatus was set to alternate the direction of rotation, the electrodes would rotate at 150rpm in one direction (e.g. clockwise), and then at 150rpm in the other direction (e.g. anticlockwise). The yield was determined when current of 5- 25mA was applied across the rotating electrodes.

[0268] Figure 18 shows a graph of yield against current for the 3D printed rotatable apparatus performing the reaction.

[0269] For the same current (i.e. 5mA), yields obtained with the rotating electrodes were higher than those without stirring or with a stirrer bar. Yields obtained where the direction of rotation of the electrodes was configured to alternate were always higher than those obtained with electrodes configured to rotate in a continuous direction.

[0270] The highest known yield for the target reaction was attained when a current of 15mA was applied across the electrodes. In this case, yields of 85% and 99% were obtained with the corotating and contrarotating electrodes respectively.

[0271] A decrease in yield was observed at higher current values, which was thought to be due to loss of product caused by over-oxidation. However, this improved electrochemical performance likely corresponds to the increased turbulence caused by alternating rotation, which ensures efficient mixing and mitigates undesired transformations such as over-oxidation. Notably, the alternating rotation also demonstrated improved performance at elevated currents. This observation suggests that the rate at which starting material is replenished surpasses the rate of overoxidation.

[0272] Without being bound by theory, this enhanced performance may be attributed to two main factors: improved mass transport due to the rotation of the electrodes, and increased surface area leading to lower current densities. The rotational movement is believed to facilitate the rapid replenishment of the starting material on the electrode surface, thereby minimizing overoxidation / overreduction. Simultaneously, the lower current densities likely mitigated intermolecular reactions.

[0273] The improved performance of the alternating direction of rotation is likely due to the increased turbulence, which ensures even more efficient mixing and mitigates undesired transformations such as over-oxidation. Notably, compared to the continuous rotation, alternating rotation also demonstrated even higher performance at the elevated current value of 25mA (68% compared to 55%). This observation suggests that the rate at which starting material is replenished surpasses the rate of overoxidation.

[0274] Computational Fluid Dynamics (CFD) Simulations

[0275] Figure 19 of the accompanying drawings shows a CAD image of a rotating electrode apparatus, where each electrode can rotate (or remain stationary) independently of the other.

[0276] CFD simulations were conducted on a) both electrodes corotating at 500rpm, b) both electrodes alternating rotation direction every 0.2 s at 500rpm, c) anode alternating rotation direction every 0.2 s at 500 rpm while the cathode remains stationary, and d) both electrodes contrarotating relative to one another while alternating rotation direction every 0.2 s.

[0277] The aim was to further enhance mixing by introducing desirable fluid formations, e.g., turbulent vortices.

[0278] A) both electrodes corotating at 500 rpm (runtime = 0.3s)

[0279] A distinct well began to form at 0.1 s and persisted as the rotation progressed. The velocity diagrams at 0.1 s show the formation of horizontal vortices near the reactor wall. Vertical vortices were absent. Instead, motion between the concentric rings appeared dominant initially. By 0.3 s, a steady state emerged in the horizontal flow dynamics without significant turbulence or vortices. This smooth flow is likely because the solvent motion begins to follow the rotation direction. However, the vertical plane exhibited numerous vortices localised near the reactor's stationary walls. These formations induced robust convection and potentially efficiently replenish the electrode surface.

[0280] B) alternating (i.e. reversing) the rotation of both electrodes every 0.2 s at 500 rpm (runtime = I s)

[0281] As usual when stirring a liquid, a well was initially formed when the rotation began. Interestingly, the initial well collapsed when the rotation direction was reversed repeatedly, which is advantageous in terms of maintaining electrode submersion and optimizing current density.

[0282] As confirmed by cross-sectional velocity analysis, at 0.2 s the fluid dynamics mirrored the standard rotation discussed for rotation profile A). However, substantial turbulence was evident shortly after the rotation reversal (0.225 s) in both horizontal and vertical planes (demonstrated by vortices throughout the section planes). After the direction of rotation was reversed, numerous horizontal vortices emerged between the electrodes. This added turbulence is hypothesised to enhance overall convection, increasing the rate of starting material replenishment at the electrode surface.

[0283] C) one electrode remaining stationary, while other electrode alternated between clockwise and anticlockwise rotation every 0.2 s

[0284] Previous simulations demonstrated the increased formation of vortices between a moving and stationary body. Enhanced vortex formation was anticipated by maintaining one electrode static, potentially elevating mixing and boosting paired electrolysis performance.

[0285] A steady state was reached in the horizontal plane before rotation reversal. Although horizontal vortices remained absent, there was a marked increase in vertical vortices. Shortly after reversing the rotation, horizontal and vertical vortices were present, suggesting better mixing potential.

[0286] D) both electrodes contrarotating relative to one another while alternating rotation every 0.2 s. It was hypothesised that contrarotating the electrodes would drive the formation of turbulent vortices, enhancing mixing while also being optimal for paired electrolysis.

[0287] Encouragingly, even before reversing rotation, pronounced turbulence was observed, with horizontal and vertical vortices being present. Shortly after reversing the rotation, the turbulence persisted, with vortices in both planes. This result suggests that the counter-rotating profile would achieve the best mixing performance.

[0288] Example 6: 3D printed electrochemical flow cell

[0289] The composite of Example la was used to prepare a photoelectrochemical flow cell, whereby the composite formed two electrically isolated interdigitated electrodes, sandwiched between two sheets of colourless transparent polypropylene. Figure 20 of the accompanying drawings shows CAD renderings of the photoelectrochemical flow cell. Figure 20 specifically shows the 3D printed flow cell A, which has an inlet and an outlet that are each equipped with ! ”-28 connectors, ensuring the compatibility of the flow cell with a wide range of existing flow equipment. The flow cell has an interdigitated configuration B, where the electrodes serve as the boundaries of the flow channels. Transparent material (e.g. polypropylene) can be positioned either side of (i.e. above and below) the interdigitated electrodes, thereby providing clear visibility into the flow channels for irradiation and / or monitoring of a reaction. The flow cell has a layered design C, whereby the electrodes are encased effectively within polypropylene. The cell may withstand internal fluid pressures of up to 10 bar. The photoelectrochemical flow cell is also shown by Figure 21 of the accompanying drawings.

[0290] The photoelectrochemical flow cell was used to perform the following reaction. This reaction had been developed under batch conditions but was not previously able to be tested under flow conditions due to the lack of suitable photoelectrochemical flow cell apparatus.

[0291] The flow rate and current applied to the solution in the flow cell was varied. The results are shown by the table below:

[0292] Figure 21 (right-hand image) shows the reaction in operation in the flow cell.

[0293] The results show that the photoelectrochemical flow cell successfully performed the reaction in a continuous, single pass process. The use of the flow cell rather than batch conditions provided enhanced productivity. This result highlights the potential for scaling up and improving efficiency through the utilization of 3D-printed electrochemical apparatus.

[0294] Figure 22 of the accompanying drawings shows CAD renderings of an alternative configuration of a photoelectrochemical flow cell. Figure 22 (top) specifically shows the electrodes, which are positioned on the same plane and interdigitated with one another. Figure 22 (bottom) shows a cut-through image of the flow cell. The flow cell includes a serpentine conduit that extends across a plane parallel to the plane of the electrodes. The cut-through image is taken through the centre of the conduit, in the plane of the conduit. The conduit is laterally fluidly enclosed. The path of the conduit is predominantly perpendicular to the length of the interdigitations of the electrodes, and turns in its serpentine pathway to return in a direction perpendicular to the length of the interdigitations of the electrodes. The plane of the electrodes and the plane of the conduit are adjacent to one another. The cut-through image reveals that the perpendicular arrangement of the conduit and the electrodes, and the interdigitation of the electrodes form a plurality of sections of the inner surface of the conduit, separated by electrically insulating material. This allows both electrodes to contact one side of the conduit. It will be understood that such interdigitation is not required, for example if one electrode contacts one side of the conduit and the other electrode contacts the other side of the conduit. Electrically insulating material also makes up the remainder of the conduit. Along the length of the conduit the electrodes that form the sections of the inner surface of the conduit alternate between the two electrodes. In use, where a potential difference is applied across the electrodes, this configuration results in a fluid flowing through the conduit being exposed to alternating polarities of potential difference. As a fluid (e.g. reaction mixture) moves through the flow path, the disruption of the diffuse layer can enhance mixing and improve mass transport.

[0295] Temperature-controlled flow cell

[0296] To enable active temperature control (e.g. cooling) capabilities, a jacketed flow cell was designed. The temperature-controlled flow cell is shown by Figure 23 of the accompanying drawings: water-cooled flow cell, CAD design (A), photograph of 3D-pnnted flow cell (B), upper coolant flow channel (C), reaction mixture flow channel (D), lower coolant channel (E), side section plane showing coolant and reaction channels (F). The design comprised the standard flow cell with an additional coolant flow path directly above and below the reaction channel (Figure 23, F).

[0297] The temperature-controlled flow cell was used to perform the high current synthesis of pinacols. Previous attempts at a high current synthesis of pinacols in flow had caused the solvent, THF, to boil. The water-cooled flow cell was employed to circumvent this issue. Additionally, the THF was switched to DMF, a high boiling point solvent. Ice-cold water was circulated via the jacket during the reaction.

[0298] Figure 24 shows the results of this experiment. Compared to THF, DMF resulted in slightly reduced yields at low currents. While the yields also dropped off rapidly at higher currents, the amount of starting material and product (SM+P) remained high, suggesting a reduction in faradaic efficiency. The reduced efficiency may be due to the rate of electron transfer surpassing the rate of mass transport i.e., insufficient mixing. Surprisingly, a current of 643 mA was achievable, representing a 32 times current increase compared to the reported literature, and a product yield of 11.53 g / day. This result demonstrates the jacketed flow cell's capabilities at active cooling and the composite’s stability under exposure to solvent and high current loads.

[0299] Pseudo-alternating polarity flow cell

[0300] A flow cell to facilitate enhanced mixing compared with the standard flow cell was developed. The flow cell comprised two standard flow cells stacked on top of each other. However, the spatial polarity of the electrodes in the upper level was reversed. Figure 25 of the accompanying drawings shows a CAD drawing of this flow cell. Figure 26 of the accompanying drawings is a schematic representation of (A) the electrode polarity, (B) the channel configuration, and (C)- (F) the flow path of the reaction mixture (“solvent”).

[0301] As the solvent progresses, it traverses one length of the cell (Figure 16, C) and then ascends to the second level, where the electrode polarity has reversed (Figure 16, D). Once on the upper level, the solvent traverses back and forth before descending back to the lower level (Figure 16, E). As the solvent moves through the cell, it is continuously directed between the two levels, effectively swapping the diffuse layers of the electrodes (Figure 16, F).

[0302] The performance of the one-layered (“standard”) flow cell, disclosed above, was compared to that of the pseudo-alternating polarity flow cell. The anode material was conductive carbon in polypropylene, and the cathode material was nickel particles in polypropylene. Optimal conditions were used in each case: 2.3 F, 0.1 mLmin1, 15 mA. The19F NMR yield was 49% for the standard flow cell. The flow cell with pseudo-alternating polarity between each level provided a yield of 62%. It was hypothesised that this movement between different polarity electrodes along the flow path replenished the anode with fresh starting material.

[0303] Standard Flow Cell 49% udo Alternating Flow 62% Large scale flow cell

[0304] Figure 17 of the accompanying drawings shows an alternative configuration of the 3D printed flow cell, which has a larger area. The flow cell of Figure 17 had a path length of 8 meters and an electrode surface area of 160 cm2. A hand is held behind the flow cell to illustrate the transparency of the polypropylene layers to visible light.

[0305] The large scale flow cell shown in Figure 17 was used for to synthesise pyrazolidin-3, 5-diones, according to the reaction scheme below. The conditions used were: 71 mA, 2.2 F, 0.5mL min ' .

[0306] Scaling the optimised conditions for the increased electrode surface area resulted in an identical yield of 49%, compared to the yield for the standard reactor discussed above. Typically scaling up a reaction will decrease the yield of product, so the maintenance of the yield is a surprising benefit.

Claims

CLAIMS1. A composite for an electrochemical apparatus, wherein the composite comprises: a polymer selected from the list consisting of poly(halo)olefin, poly(thio)ether and polyimide, and a particulate additive, wherein the particulate additive comprises an electrically conductive form of carbon, a metal or a mixture thereof.

2. The composite of claim 1, wherein the polymer is selected from the list consisting of: polyetheretherketone, polyetherketoneketone, polyaryletherketone, polyphenylene sulfide, polyphenylene sulfone, polyetherimide, thermoplastic polyimide, polyvinylidene fluoride, fluorinated ethylene propylene, and polypropylene.

3. The composite of claim 2, wherein the poly(halo)olefm is polypropylene.

4. The composite of any preceding claim, wherein the particles of the particulate additive have an average diameter of from lOnm to 40pm.

5. The composite of any preceding claim, wherein the particulate additive has a surface area of 1 m2 / g or more.

6. The composite of any preceding claim, wherein the particulate additive is selected from the list consisting of: glassy carbon, graphene, and amorphous carbon.

7. The composite of any preceding claim, wherein the particulate additive comprises two or more electrically conductive forms of carbon.

8. The composite of claim 7, wherein the particulate additive comprises a mixture of amorphous carbon and graphene9 The composite of any preceding claim, wherein the particulate additive comprises two or more metals.

10. The composite of any one of claims 1 to 5 and 9, wherein the metal is selected from the list consisting of Ag, Fe, Cr and Ni, and alloys thereof.

11. The composite of claim 10, wherein the metal is silver and / or nickel.

12. The composite of claim 1, wherein: the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene, polybutene, polypentene, polyhexene, polyseptene, polyoctene, polyetheretherketone, polyetherketoneketone, polyaryletherketone, polyphenylene sulfide, polyphenylene sulfone, polyetherimide, thermoplastic polyimide, polyvinylidene fluoride, fluorinated ethylene propylene, and a copolymer thereof; and the particulate additive is selected from the list consisting of amorphous carbon, graphite, graphene, glassy carbon, carbon nanotubes, carbon nanofibers, fullerenes, doped diamond, and conducting polymers, and Ag, Au, Fe, Zn, Pt, Ni, Al, Bi, Sn, Sb, Pb, Ag, In, Cu and Cr, and alloys thereof.

13. The composite of claim 12, wherein the polymer is selected from the list consisting of polyetheretherketone, polyetherketoneketone, polyaryletherketone, polyphenylene sulfide, polyphenylene sulfone, polyetherimide, thermoplastic polyimide, polyvinylidene fluoride, fluorinated ethylene propylene, and polypropylene.

14. The composite of claim 12 or 13, wherein the particulate additive is two or more electrically conductive form of carbon selected from the list consisting of amorphous carbon, graphite, graphene, glassy carbon, carbon nanotubes, carbon nanofibers, fullerenes, doped diamond and conducting polymers.

15. The composite claim 12, wherein: the polymer is selected from the list consisting of polyethylene, polypropylene, polymethylpentene and polybutene, or a copolymer thereof, the particles of the particulate additive have an average diameter of from lOnm to 40pm, and the particulate additive is selected from the list consisting of: amorphous carbon, graphite, graphene, Ag and Ni.

16. An article comprising the composite of any one of claims 1 to 15.

17. The article of claim 16, wherein the article is an electrochemical apparatus, an electrochemical reactor, an electrode, a sensor, battery, or a fuel cell.

18. A method for producing a composite, wherein the composite is for electrochemical apparatus, wherein the method comprises: providing a polymer selected from the list consisting of polyolefin, poly(thio)ether and polyimide, providing a particulate additive, wherein the particulate additive comprises an electrically conductive form of carbon, a metal or a mixture thereof, combining the polymer with the particulate additive to provide a composite precursor, and heating the composite precursor to melt the composite precursor and form the composite.

19. The method of claim 18, wherein the step of combining the polymer with the particulate additive comprises: dissolving the polymer in an organic solvent to form a solution of the polymer in the organic solvent, dispersing the particulate additive in the solution so as to provide a dispersion, and cooling the dispersion and / or adding an anti-solvent to the dispersion to precipitate the composite precursor.

20. The method of claim 19, wherein the step of combining the polymer with the particulate additive to provide a composite precursor comprises mixing the solid polymer with the particulate additive.

21. An electrochemical screening apparatus for simultaneously screening a plurality of electrochemical reactions, the electrochemical screening apparatus comprising:(a) a body comprising a plurality of cavities, and(b) a plurality of pairs of electrodes, wherein the electrodes of each pair are electrically isolated from one another, wherein each pair of electrodes is physically connected to one another, and wherein the electrodes of each pair are separately electrically connected to the electrodes of another pair; wherein each pair of electrodes is configured in relation to one of the cavities such that, in use when there is an electrolyte in the cavity, the electrolyte can make electrical contact between the electrodes of the pair of electrodes in the cavity.

22. The electrochemical screening apparatus of claim 21, wherein each pair of electrodes is held by one or more electrode mountings in the wall of each cavity23. The electrochemical screening apparatus of claim 21, wherein each pair of electrodes is held by a head, such that in use the electrodes can extend into the cavity.

24. The electrochemical screening apparatus of claim 22, wherein the body is a well plate.

25. An electrochemical apparatus comprising: a head, a body, and a pair of elongate electrodes, and wherein: the body is able to rotate about an axis relative to the head, the body and the head are secured to one another, one or both of the pair of electrodes is or are configured to rotate with the body, the electrodes extend in substantially the same direction as one another, the direction in which the electrodes extend is substantially parallel with the axis of rotation, and the electrodes are electrically isolated from one another.

26. The electrochemical apparatus of claim 25, wherein the apparatus comprises a plurality of pairs of elongate electrodes.

27. The electrochemical apparatus of claim 25 or claim 26, wherein the electrodes of the pair of elongate electrodes are configured to corotate and / or contra-rotate relative to one another; and the electrodes are arranged:- such that, in use, the polarity of the electrodes alternates about the axis, and / or- in layers such that the polarity of the electrodes alternates radially.

28. The electrochemical apparatus of any one of claims 25 to 27, wherein there are apertures through the electrodes and / or protuberances on the surface of the electrodes.

29. The electrochemical apparatus of any one of claims 25 to 28, wherein both electrodes of the pair of electrodes are electrically connected to an electrical terminal in the head.

30. The apparatus of the claim 25, wherein the apparatus comprises: a first body, a second body, a first electrode of the pair of electrodes, and a second electrode of the pair of electrodes; wherein the first body is attached to or unitary with the first electrode, and the second body attached or unitary with the second electrode, and wherein the apparatus is configured such that the first electrode and / or the second electrode can rotate about an axis.

31. A method of operating an electrochemical apparatus comprising a pair of electrodes, wherein one or both of the electrodes is or are configured to move, wherein the method comprises, whilst the electrodes are in contact with a reaction medium, and whilst a potential difference is applied across the electrodes, moving one or both of the electrodes through the reaction mixture in a first direction, and moving the one or both of the electrodes through the reaction mixture in a second direction.

32. The method of claim 31, wherein one or both of the electrodes are specifically configured to rotate such that they move through the reaction medium, and the first direction and the second direction correspond to clockwise rotation and anticlockwise rotation.

33. An electrochemical apparatus comprising a flow cell, wherein the flow cell comprises: a fluid inlet, a fluid outlet, and two sheets of electrically isolating material, wherein the two sheets of electrically isolating material are spaced apart by a pair of electrodes, wherein the electrodes are interdigitated with one another, wherein the electrodes are electrically isolated from one another, and wherein a void between the interdigitations of the electrodes defines a conduit that allows fluid to pass from the fluid inlet to the fluid outlet.

34. The electrochemical apparatus of claim 33, wherein the electrically isolating material transmits ultraviolet, visible and / or infrared radiation.

35. The electrochemical apparatus of claim 33 or claim 34, wherein one or both of the sheets of electrically isolating material comprise one or more conduits for temperature control fluid.

36. The electrochemical apparatus of any one of claims 33 to 35, wherein the apparatus comprises two or more flow cells fluidly connected in series, and configured such that the polarity of the electrodes of two adjacent flow cells is alternated with respect to one another.

37. An electrochemical flow cell comprising a conduit and a pair of electrodes, wherein each electrode defines a plurality of sections of the inner surface of the conduit, and wherein the sections are arranged along the length of the conduit and alternate between the electrodes along the length of the conduit, and wherein electrically isolating material separates the electrodes such that, in use, when a potential difference is applied across the electrodes, a fluid flowing through the conduit is exposed to alternating polarities of potential difference as it flows through the conduit.

38. The electrochemical flow cell of claim 37, wherein electrodes are both located on one side of the conduit.

39. The electrochemical flow cell of claim 37 or claim 38, wherein the path of the conduit is predominantly perpendicular to the length of the interdigitations of the electrodes.

40. The electrochemical screening apparatus, the electrochemical apparatus, the method, or the electrochemical flow cell of any one of claims 21 to 39, wherein the electrodes are each independently made of the composite of any one of claims 1 to 15.

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