Direct alcohol fuel cell

Abstract

A direct alcohol fuel cell having an inner housing, and a proton exchange membrane separating an anode section from a cathode section. The anode section contains an anode collection element electrically connected to an anode catalyst that is in diffusive communication with a fuel supply. The cathode section contains a cathode collection element having one or more ventilation holes is electrically connected to a cathode catalyst. An oleophobic filter and/or an anion-exchange membrane is provided, which cathode catalyst via the one or more ventilation holes and the oleophobic filter and/or the anion-exchange membrane is in diffusive communication with a gaseous oxidant. The inner housing has a bottom and walls extending from the bottom to contain the anode section, the PEM and the cathode section, the bottom and/or the walls having holes allowing fluid communication from a fuel supply to the anode section. The fuel cell is suited for microelectronic devices.

Claims

1. A direct alcohol fuel cell (DAFC) comprising an inner housing, and a proton exchange membrane (PEM) separating an anode section from a cathode section, wherein the anode section contains: an anode collection element electrically connected to an anode catalyst, which anode catalyst is in diffusive communication with a fuel supply, and wherein the cathode section contains: a cathode collection element having one or more ventilation holes, which cathode collection element is electrically connected to a cathode catalyst, which cathode catalyst via the one or more ventilation holes is in diffusive communication with a gaseous oxidant, the inner housing having a bottom and walls extending from the bottom to a length sufficient to contain the anode section, the PEM and the cathode section, the bottom and/or the walls having holes allowing fluid communication from a fuel supply to the anode section.

2. The DAFC according to claim 1, wherein the inner housing is made from an electrically conductive metal.

3. The DAFC according to claim 1, wherein the inner housing is made from an electrically non-conductive thermoplastic elastomer.

4. The DAFC according to claim 3, wherein the inner housing is coated with an electrically conductive metallic surface or equipped with tracks of an electrically conductive metal.

5. The DAFC according to claim 1, wherein the inner housing is the anode collection element or the cathode collection element.

6. The DAFC according to claim 1, wherein the PEM has a first dimension and a second dimension, the ratio of the first dimension to the second dimension is in the range of 1:10 to 10:1.

7. The DAFC according to claim 1, wherein the anode section contains a pervaporation membrane.

8. The DAFC according to claim 1, wherein the cathode section contains an anion-exchange membrane.

9. The DAFC according to claim 1, wherein the DAFC further comprises an external housing with a fuel reservoir in fluid communication with the holes of the inner housing.

10. A microelectronic device comprising a DAFC according to claim 1.

11. A method of operating a DAFC, the method comprising the steps of: providing a DAFC according to claim 1; supplying a fuel comprising an aqueous solution of methanol at a concentration of at least 10 M to the DAFC.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the invention will be explained in greater detail with reference to the schematic drawings, in which

(2) FIG. 1 shows an exploded drawing of fuel cell components of a direct alcohol fuel cell (DAFC) of the invention;

(3) FIG. 2 shows a top view of a power pack of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) The present invention relates to a direct alcohol fuel cell (DAFC), to a microelectronic device and to a method of operating a DAFC of the invention. The DAFC has an inner housing having a bottom and walls extending from the bottom to a length sufficient to contain the anode section, the PEM and the cathode section.

(5) The DAFC of the present invention is especially suited for a microelectronic device. The microelectronic device may be any electronic device requiring a power input up to 30 mW, e.g. in the range of 1 mW to 10 mW. The microelectronic device may be any microelectronic device, but a preferred microelectronic device is a hearing aid.

(6) The DAFC of the present invention may use any alcohol as fuel. Preferred fuels include methanol and ethanol. When the DAFC employs methanol as a fuel it may also be referred to as a direct methanol fuel cell (DMFC). Correspondingly, the DAFC may be a direct ethanol fuel cell (DEFC). The alcohol will typically be provided as an aqueous solution, and the concentration of the alcohol may be chosen freely. Typical concentrations of methanol (in water) for DMFCs are in the range of 1 M to 3 M, but in the DAFC of the present invention the cell design allows a much higher concentration, i.e. up to pure methanol corresponding to 24.7 M, and the concentration of methanol will typically be at least 5 M, e.g. in the range of 10 M to 24.7 M, such as about 20 M. In a DAFC the alcohol is gradually oxidised to eventually be converted to H.sub.2O and CO.sub.2 as waste products. Consequently, in the context of DAFCs the intermediary oxidation states from the alcohol to the final waste products may also be employed as fuel, e.g. for a DMFC formaldehyde and formic acid may also be used as fuel.

(7) The DAFC contains a proton exchange membrane (PEM). The PEM may also be referred to as a polymer electrolyte membrane, and the two terms may be used interchangeably. At the PEM protons are supplied through a catalytic process of the fuel, and any material with this property may be employed. Exemplary PEMs comprise the perfluorosulphonic acid ionomer sold under the trade name Nafion (e.g. N1110 or Nafion 117) by DuPont who developed it in the 1961s. Other examples of appropriate materials employ linear polymers, such as styrene, styrene-derivatives, poly(arylene ether)s, sulphonation of existing aromatic polymers, co-polymers from sulphonated monomers, poly(imide)s, altered backbone polymers, poly-phosphazene. Yet other approaches have involved the introduction of silica in polymer electrolyte membrane polymer formulations.

(8) The DAFC contains catalysts in the anode section and in the cathode section. The catalysts generally comprise a catalytic metal, e.g. platinum or platinum-ruthenium, on a support material, e.g. carbon, with electron conductive properties. Appropriate metals for the anode catalyst and the cathode catalyst are well-known to the skilled person who can select the metals freely. Likewise, support materials may also be selected freely. For example, the catalyst may comprise particulate, e.g. nanoparticulate, carbon, with catalyst nanoparticles of platinum or platinum-ruthenium. Appropriate catalysts structures, and their manufacture, for the DAFC are disclosed in WO 2014/005598. Another catalyst is known as Johnson Matthey HiSPEC 13100 which is platinum, nominally 70% on high surface area advanced carbon support.

(9) The DAFC may contain other components as desired. For example, the DAFC may employ water management layers, e.g. microporous structures, and gas diffusion layers, e.g. a microporous layer on which the catalytic structure may be situated, e.g. platinum on a carbon support, which provides the catalytic conversion of the fuel to an electrical current. Likewise, the DAFC may contain gaskets and the like for making the DAFC and its layers fluid tight and for providing electrical insulation at appropriate sites, e.g. between terminal sites.

(10) An exploded drawing of fuel cell components is depicted in FIG. 1. Briefly summarised, FIG. 1 depicts an embodiment of the DAFC 1 of the invention. The DAFC 1 has a PEM 2 separating the anode section from the cathode section. The anode section contains an anode collection element 41 electrically connected to an anode catalyst layer 42. Between the anode collection element 41, which is shaped to be an inner housing by having a bottom 411 and walls 412 extending from the bottom 411 to a length sufficient to contain the anode section and also the cathode section, and the anode catalyst layer 42 is a pervaporation membrane 44, a spacer insert layer 45 and an anode diffusion layer (or water management layer) 43. The cathode section contains a cathode collection element 31 with ventilation holes 311 and electrically connected to a cathode catalyst layer 32, and between the cathode collection element 31 and the cathode catalyst layer 32 is a cathode diffusion layer (or water management layer) 33. The cathode section further comprises an oleophobic filter 34, and it may additional comprise an anion-exchange membrane (not shown). Finally, the DAFC 1 contains isolator 51, gasket 52 and weld plate 50, that are used to assemble the DAFC 1. When the anode collection element 41, or anode cup 41, is finally assembled to contain both the anode section and the cathode section, the assembly is thus a power pack for a fuel cell. The power pack may be inserted in an external housing 10. The external housing 10 has a fuel inlet 101, and the anode cup 41, which has holes 413 providing fluid communication with the fuel reservoir (not shown) in the external housing 10. Specifically, the external housing 10 is attached to the power pack to form the reservoir.

(11) FIG. 2 shows a top view of the partly assembled power pack. The features shown in the embodiment in FIG. 1 and FIG. 2 are discussed more elaborately below in Example 1.

EXAMPLES

Example 1

(12) In the embodiment depicted in FIG. 1, the inner housing is the anode collection element 41. The anode collection element 41 may also be referred to as an “anode cup”, and the term “anode cup” will also refer to the inner housing when the inner housing is the anode collection element 41. Likewise, the reference numeral 41 also refers to the anode cup 41.

(13) The anode collection element 41 is prepared from AISI 316L stainless steel. Specifically, a sheet of 0.2 mm stainless steel has been punched to provide the anode cup so that the bottom 411 has an area of 8.35 mm×4.80 mm corresponding to the size of the fuel cell components in the anode section. The anode cup 41 may be coated with gold. The anode cup 41 has a height sufficient to house the anode section and also the cathode section as explained below.

(14) The bottom 411 of the anode cup 41 has holes 413, e.g. 5 holes 413 of a diameter of about 500 μm that allow fluid communication across the bottom 411. Alternatively, the holes 413 may be in the range of 100 μm to 1500 μm.

(15) A pervaporation membrane 44 of 8.35 mm×4.80 mm size and a thickness of 150 μm is placed at the bottom 411 of the anode cup 41. The pervaporation membrane 44 consists of a poly-tetrafluoroethylene (PTFE) backbone with perfluoroether pendant side chains terminated by sulphonic acid; an exemplary pervaporation membrane 44 is marketed by Solvay under the trademark Aquivion E98-155. The pervaporation membrane 44 allows methanol vapour to pass through from a liquid fuel so that the pervaporation membrane 44 provides pervaporative communication from below the anode cup 41 to the anode section. Furthermore, the negative charges of the sulphonic acid groups provide a cation-exchange function so that metal ions are sequestered from liquids diffusing into the pervaporation membrane 44, and thereby metal ion contamination of the DAFC 1 is avoided. However, the pervaporation membrane 44 may also be a PTFE backbone without charged groups. Such a pervaporation membrane 44 prevents direct fluid communication from the fuel supply to the PEM while still allowing pervaporative communication, and thereby also diffusive communication. The distance from the PEM 2 to the pervaporation membrane 44 may also be referred to as the spacing distance.

(16) On top of the pervaporation membrane 44 is placed a spacer insert 45. The spacer insert 45 may also be referred to as a PM insert. The spacer insert 45 has been prepared from a 100 μm sheet of AISI 316L stainless steel, and it has 5 holes 451, e.g. distributed as shown in FIG. 1, of 1.2 mm diameter. The spacer insert 45 may be coated with gold, as is done in the present embodiment. The spacer insert 45 improves the electrical connection between the anode catalyst layer 42 and the anode cup 41, and the holes 451 allow access of the fuel, e.g. methanol, to the anode catalyst 42 layer.

(17) The distance between the PEM 2 and the spacer insert 45 is about 500 μm, and about halfway between the PEM 2 and the spacer insert 45 the wall 412 of the anode cup 41 has, e.g. in the middle of the longer wall section of the wall 412 of the anode cup 41, a venting hole 414 of a diameter of 50 μm. Specifically, the centre of the venting hole 414 is placed at about 250 μm from the spacer insert 45 of the anode cup 41. The venting hole 414 allows vapour of H.sub.2O and CO.sub.2 produced in the DAFC 1 to leave the anode section. When the diameter of the venting hole 414 is in the range of 25 μm to 300 μm, penetration of O.sub.2 into the anode section as well as fuel losses from the anode section are minimised. Thereby the venting hole 414 provides a more efficient DAFC 1.

(18) On top of the spacer insert 45, i.e. relative to the bottom 411 of the anode cup 41, is placed an anode diffusion layer 43 (the diffusion layer may also be referred to as a water management layer). The anode diffusion layer 43 is a fibrous carbon material that is generally known as carbon paper. The carbon fibre material may also have a microporous layer of carbon particles and the carbon fibre substarte and/or the microporous layer may have a hydrophobic, e.g. a PTFE-derivatised, treatment. Being fibrous, the anode diffusion layer 43 can be compressed but its thickness in an uncompressed state is 250 μm, and furthermore, the fibrous material may be described with an area weight; an appropriate area weight is in the range of 120 g/m.sup.2 to 150 g/m.sup.2. An exemplary fibrous material to use for the anode diffusion layer 43 is marketed as H23C6 by Freudenberg.

(19) The spacer insert 45 and the anode diffusion layer 43 have dimension corresponding to the bottom 411 of the anode cup 41, i.e. 8.35 mm×4.80 mm, but the sizes of the spacer insert 45 and the anode diffusion layer 43 are not critical and smaller dimension are also possible, e.g. to 80% of the dimensions of the bottom 411 of the anode cup 41.

(20) The anode catalyst layer 42 and the cathode catalyst layer 32 each comprise a substrate carbon cloth and a layer of a support material with catalytic metal nanoparticles; the support materials are carbon particle materials with high specific surface areas. In this embodiment, the anode catalyst layer 42 and the cathode catalyst layer 32 may also be referred to as gas diffusion electrodes. Thus, a gas diffusion electrode, i.e. the anode catalyst layer 42, is then placed on top of the anode diffusion layer 43 relative to the bottom 411 of the anode cup 41. The anode catalyst layer 42 is a carbon cloth substrate with a layer of carbon support with a high specific surface area carrying catalytic nanoparticles. For example, the carbon support may carry appropriate metallic nanoparticles having a specific surface area of at least 50 m.sup.2/g. A typical catalyst layer has about 20% to 80% by mass of metal to carbon. The anode catalyst layer 42 has a mixture of platinum and ruthenium as the catalytic metal. An appropriate anode catalyst material is marketed by Johnson Matthey under the trademark HiSpec, e.g. HiSpec 13100, HiSpec 12100, etc. The thickness of the anode catalyst layer 42 in FIG. 1 is 500 μm to 600 μm when the anode catalyst layer 42 is in an uncompressed state. Of this value the catalyst layer is about 150 μm to 250 μm.

(21) The PEM 2 is placed on the anode catalyst layer 42. In this embodiment, the PEM 2 is structured to have a bottom 21 and walls 22 extending from the bottom 21 to a containment distance into the cathode section; the containment distance is sufficient to contain the cathode section. In this embodiment the PEM 2 may also be referred to as the PEM cup 2, and the reference numeral 2 will also refer to the PEM cup 2. By having PEM cup 2 housing the cathode section, which in turn is housed in the anode cup 41, a very compact design of the DAFC 1 is obtained. Since the PEM cup 2 is contained in the anode cup 41, the area of the bottom 21 of the PEM cup 2 is correspondingly smaller. In the present embodiment, the bottom 21 has dimensions, i.e. dimensions inside the PEM cup 2, of 8.05 mm×4.50 mm.

(22) The PEM 2 may be made from any material allowing selective transportation of protons across the membrane. Typically, the PEM 2 is made from a polymeric material having a PTFE backbone with perfluoroether pendant side chains terminated by sulphonic acid. Exemplary materials are marketed by Dupont under the trademark Nafion. In the embodiment depicted in FIG. 1, the PEM 2 is Nafion 117 with a thickness of about 175 μm. The PEM cup 2 has been shaped, e.g. hot-pressed. from a single sheet of Nafion 117. Thereby, the PEM 2 can also serve as a gasket to prevent undesired fluid communication to the cathode section and the area of the anode cup 41 is used more efficiently so that a larger effective area is achieved.

(23) A gas diffusion electrode, i.e. the cathode catalyst layer 32, is then placed in the PEM cup 2. The same materials as relevant for the anode catalyst layer 42 are relevant also for the cathode catalyst layer 32. In the embodiment of FIG. 1, a HiSpec 13100 material is deposited together with Nafion on a carbon cloth and is cut to dimensions of 8.05 mm×4.50 mm, and the thickness of the cathode electrode layer 32 is 450 μm to 500 μm when the cathode catalyst layer 32 is in an uncompressed state of which the catalyst layer is 100-150 μm.

(24) A cathode diffusion layer 33 is placed on the cathode catalyst layer 32. As for the anode diffusion layer 43, the cathode diffusion layer 33 is also H23C6, and the same materials are relevant for both diffusion layers.

(25) The cathode catalyst layer 32 and the cathode diffusion layer 33 are shown with an isolator 51 between them. In the embodiment of FIG. 1, the isolator 51 is made from the electrically insulating material Kapton HN500 (as marketed by Dupont). Kapton is a polyimide film, and any polyimide film may be used for the isolator 51. The isolator 51 has a thickness of about 50 μm, and in FIG. 1 the isolator 51 is shown with a flap 511 placed at an approximate right angle to the isolator 51. Upon assembly of the power pack the flap 511 will extend from the PEM cup 2 and the anode cup 41 through cut-outs in the walls of PEM cup 2 and the anode cup 41. Thus, the wall 22 of the PEM cup 2 may have an opening 221, e.g. a cut-out, and wall 412 of the anode cup 41 may have an opening 415, e.g. a cut-out; the openings are aligned to allow the flap 511 to extend through them. After assembly the flap 511 may be placed along the wall of the external housing 10, if used, or the anode cup 41 in order to provide a site for a cathode terminal that is electrically insulated from the anode cup 41, including the bottom of the cut-out 415.

(26) The isolator 51 has a cut-out section allowing physical contact between the cathode catalyst layer 32 and the cathode diffusion layer 33 over the majority of the areas for the cathode catalyst layer 32 and the cathode diffusion layer 33.

(27) A cathode collection element 31 with ventilation holes 311 is placed in contact with the cathode diffusion layer 33. The ventilation holes 311 allow diffusion of gaseous oxidant to the PEM 2 and waste gasses away from the PEM 2.

(28) The cathode collection element 31 has been stamped from a 200 μm sheet of AISI 316L stainless steel, which has subsequently been coated with gold. The cathode collection element 31 is shown with 6 ventilation holes 311 but fewer or more ventilation holes 311 may also be used. In the depicted embodiment, the ventilation holes 311 are rectangular with dimensions of 1.2 mm×0.9 mm.

(29) The cathode collection element 31 has a cathode terminal site 312 shown at a right angle to the cathode collection element 31. The placement of the cathode terminal site 312 complies with the flap 511 of the isolator 51, and the cathode terminal site 312 extends through the same cut-outs in the anode cup 41 and the PEM cup 2. After assembly of the power pack the cathode terminal site 312 may be bent at a bendable segment located between the cathode collection element 312 and the cathode terminal site 312. In particular, the cathode terminal site 312 may be bent towards the anode cup 41 where the flap 511 of the isolator 51 ensures that the cathode terminal site 312 is electrically insulated from the anode cup 41 and the corresponding anode terminal. Thereby, the cathode terminal site 312 with the bendable segment allows a compact design of the power pack and also the DAFC 1.

(30) The part of the cathode collection element 31 located in the cathode section has dimensions of 8.05 mm×4.50 mm, although it is not required to have the same dimensions as the bottom of the PEM cup 2; in particular, the dimensions of the cathode collection element 31 located in the cathode section may be from 80% of the dimensions of the bottom of the PEM cup 2.

(31) On the cathode collection element 31 is placed an oleophobic filter 34 with dimensions of 8.05 mm×4.50 mm. The oleophobic filter 34 is an uncharged microporous PTFE membrane with a thickness of 180 μm and a pore size of 0.4 μm. Specifically, the oleophobic filter 34 is a PMV15T membrane from Porex. The oleophobic filter 34 prevents penetration of liquids into the cathode section while at the same time allowing penetration of gasses, e.g. waste gasses from the DAFC 1 and gaseous oxidant into the cathode section. The oleophobic filter 34 further provides electric insulation between the weld plate 50 and the cathode collection element 31.

(32) In FIG. 2, the oleophobic filter 34 is inserted in the anode cup 41, and FIG. 2 shows the cut-out 415 in the anode cup 41. The cathode terminal 312 is shown extending from the anode cup 41 via the cut-out 415. The embodiment of the oleophobic filter 34 depicted in FIG. 2 has 6 slits 341 located so as to be aligned with the six ventilation holes 311 of the cathode collection element 31, which is located below the oleophobic filter 34. The slits 341 are depicted as diagonal cuts for each ventilation hole 311. The slits 341 allow transfer of H.sub.2O as liquid, through the oleophobic filter 34. However, the DAFC 1 will also function without the slits 341.

(33) The DAFC 1 further comprises an anion-exchange membrane (not shown) located between the cathode collection element 31 and the cathode diffusion layer 33. The anion-exchange membrane may be a fumapem FAA-3-30 membrane (Fumatech BWT GmBH, Bleitigheim-Bissingen, Germany). The anion-exchange membrane may alternatively be a hydrogel with amine groups, in particular quarternary amine groups. The anion-exchange groups will sequester negatively charged ions, in particular chloride ions, from liquids diffusing through the anion-exchange membrane. Thus, when an anion-exchange membrane is employed the fuel cell interior, e.g. the cathode section, is protected from sweat. Thereby, the anion-exchange membrane provides a power pack and a DAFC 1 especially suited for use in a hearing aid.

(34) The power pack can now be finalised by welding a weld plate 50 with the anode cup 41 or the external housing 10. Thus, the weld plate 50, which has dimensions corresponding to the dimensions of the bottom of the anode cup 41 thereby allowing the enclosure of the anode section and the cathode section in the anode cup 41 is placed on top of the oleophobic filter 34, and the weld plate 50 is then welded along the edge of the weld plate 50 to the wall of the anode cup 41. The weld plate 50 may be placed in the anode cup 41 and welded to the inner wall of the anode cup 41, or the weld plate 50 may be welded to the wall of the anode cup 41 at the top of the anode cup 41. Thereby, it is ensured that the power pack is as small as possible, which further optimises diffusion of fuel and waste gasses to and from the PEM 2.

(35) The weld plate 50 has ventilation holes 501, which will be aligned with the ventilation holes 311 of the cathode collection element 31, and which have the same the same function as the ventilation holes 311, i.e. allowing diffusion of gaseous oxidant to the PEM 2 and waste gasses away from the PEM 2. The weld plate 50 has been prepared from a 200 μm sheet of AISI 316L stainless steel. The weld plate 50 will generally not have a coating as it is not used as an electrical terminal, even though by welding to the anode cup 41 any section of the weld plate 50 may serve as an anode terminal site.

(36) The now assembled power pack has dimensions of 9.0 mm×5.5 mm×2.5 mm. The full outer surface of the anode cup 41 can serve as an anode terminal site, and the power pack may have a cathode terminal site 312 extending from the power pack so that the anode terminal site and the cathode terminal site 312 may connect to corresponding terminal sites of an electrical circuit.

(37) The power pack, or the DAFC with the external housing, may comprise a gasket 52, e.g. a silicone gasket, that electrically insulates the power pack or DAFC for integration with an external microelectronic device; the gasket 52 further allows a fluid tight integration with the external microelectronic device.

(38) The power pack may be used as a DAFC with an appropriate fuel supply. However, in the embodiment depicted in FIG. 1, the power pack is placed in an external housing 10 so that the holes 413 in the anode cup 41 face a fuel reservoir contained in the external housing. The external housing 10 can be considered to be the reservoir. In the embodiment of FIG. 1, the external housing 10, i.e. the fuel reservoir, is located below the anode section and the fuel is in fluid communication with the anode section via the holes 413. The embodiment in FIG. 1 has a reservoir of a volume of about 200 μL.

(39) As depicted in FIG. 1 the external housing 10 has been prepared from a sheet of AISI 316L stainless steel, which has dimensions for the anode cup 41 to generally fit snugly onto the external housing 10 with due consideration for allowing access to the venting hole 414. Alternatively, the wall of the external housing 10 may have a hole (not shown) aligned with the venting hole 414 for allowing diffusion from the venting hole 414. In particular, a hole in the wall of the external housing 10 may be larger than the venting hole 414, since the effects obtained with the venting hole 414 will not be jeopardised by the hole in the wall in the external housing. Alternatively, the venting hole 414 and the hole in the wall of the external housing 10 may be created after fitting the anode cup 41 in the external housing 10, e.g. using laser ablation or micro drilling etc.

(40) The anode cup 41 and the external housing 10 may be welded or glued together. The anode cup 41 could also be pressed against a gasket 52. Due to the close contact between the surfaces of the anode cup 41 and the external housing 10, the outer surface of the external housing 10 may provide an anode terminal site. The wall of the external housing 10 may have a cut-out (not shown) through which the flap 511 and the cathode terminal site 312 can extend. The cathode terminal site 312 can then be bent towards the wall of the external housing 10 with the flap 511 providing electrical insulation between the external housing 10, i.e. the anode terminal site, and the cathode terminal site 312. Alternatively, the external housing 10 may be coated or otherwise covered with an electrically insulating layer to prevent short-circuits between the anode terminal site and the cathode terminal site 312; the anode terminal site may be exposed as desired by removing sections of the coating on the external housing 10.

(41) The external housing 10 has a fuel inlet 101 for replenishing the fuel in the reservoir and removing spent fuel. The external housing 10 may have any appropriate valve or valves (not shown), and it may work together with an external supply of fuel employing an appropriate pump.

REFERENCE NUMERALS

(42) 1 Direct alcohol fuel cell (DAFC)

(43) 10 External housing

(44) 101 Fuel inlet

(45) 2 Proton exchange membrane (PEM)

(46) 21 Bottom of PEM

(47) 22 Walls of PEM

(48) 221 Opening in wall of PEM

(49) 31 Cathode collecting element

(50) 311 ventilation holes of cathode collecting element

(51) 312 Cathode terminal site

(52) 32 Cathode catalyst layer

(53) 33 Cathode diffusion layer

(54) 34 Oleophobic filter

(55) 341 Slit

(56) 41 Anode collecting element

(57) 411 Bottom of anode collecting element

(58) 412 Walls of anode collecting element

(59) 413 Hole in bottom of anode collecting element

(60) 414 Venting hole

(61) 415 Opening

(62) 42 Anode catalyst layer

(63) 43 Anode diffusion layer

(64) 44 Pervaporation membrane

(65) 45 Spacer insert layer

(66) 451 Hole of the spacer insert layer

(67) 50 Weld plate

(68) 501 Ventilation hole of weld plate

(69) 51 Isolator

(70) 511 Flap of isolator

(71) 52 Gasket

(72) Although some embodiments have been described and shown in detail, the invention is not restricted to them, but may also be embodied in other ways within the scope of the subject matter defined in the following claims. In particular, it is to be understood that other embodiments may be utilised and structural and functional modifications may be made without departing from the scope of the present invention.

(73) In device claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage.

(74) It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.