CCM composite
CCM formed of a membrane having on one of the two surfaces a first electrocatalytic layer containing a catalyst and on the other one a second electrocatalytic layer containing a catalyst, said electrocatalytic layers and said membrane containing (per)fluorinated ionomers, said CCM having the following characteristics: size variations, for both the orthogonal directions of the plane xy, lower than 15%, by dipping the CCM, after drying at 105° C. under vacuum for one hour in demineralized water at 100° C. for 30 minutes; the CCM remains substantially unchanged after having been subjected to treatments of 60 cycles by dipping in water at 80° C. for 8 hours and then in water at the temperature of 25° C. for 16 hours.
1. A catalyst coated membrane (CCM) comprising a membrane having on one of the two surfaces a first electrocatalytic layer comprising a catalyst and on the other one a second electrocatalytic layer comprising a catalyst, wherein:
the orthogonal projection of the perimeter of the first electrocatalytic layer on the second layer is distant from the perimeter of the second electrocatalytic layer at least 1 mm in each point of said projection;
both the electrocatalytic layers and the membrane, comprise (per)fluorinated ionomers, and wherein the CCM has the following features:
size variations in the orthogonal directions of the plane xy lower than 15% after CCM dipping in demineralized water at 100° C. for 30 minutes, dried at 105° C. under vacuum for one hour;
the electrocatalytic layers of the CCM remain adherent to the membrane after 60 cycles by dipping in water at 80° C. for 8 hours and then in water at the temperature of 25° C. for 16 hours.
2. A CCM according to claim 1 , wherein the (per)fluorinated ionomers are sulphonic ionomers having an equivalent weight in the range from 380 to 1,700 g/eq.
3. A CCM according to claim 1 , wherein the (per)fluorinated ionomers comprise the following units:
copolymers comprising:
(A) monomeric units deriving from one or more fluorinated monomers comprising at least one ethylenic unsaturation;
(B) fluorinated monomeric units comprising sulphonyl —SO 2 F groups in amounts such that the ionomer has the equivalent weight in the above range;
homopolymers formed of monomeric units (B); subsequent ionomer hydrolysis to convert the —SO 2 F groups into sulphonic groups in acid —SO 3 H or salified form.
4. A CCM according to claim 3 , wherein the fluorinated monomers (A) are selected from the following:
vinylidene fluoride (VDF);
C 2 -C 8 perfluoroolefins;
C 2 -C 8 chloro- and/or bromo- and/or iodo-fluoroolefins;
CF 2 ═CFOR fl (per) fluoroalkylvinylethers (PAVE), wherein R fl is a C 1 -C 6 (per) fluoroalkyl;
CF 2 ═CFOX perfluoro-oxyalkylvinylethers, wherein X is a C 1 -C 12 perfluoro-oxyalkyl having one or more ether groups.
5. A CCM according to claim 3 , wherein the fluorinated monomers (B) are selected from one or more of the following:
F 2 C═CF—O—CF 2 —CF 2 —SO 2 F;
F 2 C═CF—O—[CF 2 —CX A F—O] nA —(CF 2 ) nB —SO 2 F wherein X A ═Cl, F or CF 3 ; nA=1-10, nB=2,3;
F 2 C═CF—O—CF 2 —CF 2 —CF 2 —SO 2 F;
F 2 C═CF—Ar—SO 2 F wherein Ar is an aryl ring.
6. A CCM according to claim 3 , wherein the sulphonic (per)fluorinated ionomers further comprise from 0.01% to 2% by moles of monomeric units deriving from a bis-olefin of formula:
R 1 R 2 C═CH—(CF 2 ) m —CH═CR 5 R 6 (I)
wherein:
m=2-10;
R 1 , R 2 , R 5 , R 6 , equal to or different from each other, are H or C 1 -C 5 alkyl groups.
7. A CCM according to claim 3 , wherein the (per)fluorinated ionomers comprise, optionally in admixture with the monomers with —SO 2 F groups, monomers comprising precursor groups which by hydrolysis are transformed into —COOH groups, selected from the following:
F 2 C═CF—O—CF 2 —CF 2 —Y;
F 2 C═CF—O—[CF 2 —CX A F—O] nA —(CF 2 ) nB —Y
wherein X A ═C1, F or CF 3 ; nA=1-10, nB=2,3;
F 2 C═CF—O—CF 2 —CF 2 —CF 2 —Y;
F 2 C═CF—Ar—Y wherein Ar is an aryl group;
wherein Y is a precursor group of the carboxylic group, selected from the following: CN, COF, COOH, COOR B , COO − Me + , CONR 2B R 3B , wherein R B is C 1 -C 10 and R 2B and R 3B , equal or different, are H or have the meaning of R B , Me is an alkaline metal.
8. A CCM according to claim 3 , wherein the membrane and the electrocatalytic layers comprise (per)fluorinated ionomers obtained from ionomers comprising:
monomeric units deriving from TFE;
monomeric units deriving from CF 2 ═CF—O—CF 2 CF 2 SO 2 F.
9. A CCM according to claim 1 , wherein the electrocatalytic layers comprise an ionomer and a catalyst selected between Pt or a mixture of Pt with one or more metals optionally supported on carbon.
10. A CCM according to claim 1 , wherein the ratio by weight between catalyst and ionomer in each of the two electrocatalytic layers ranges from 0.5 to 4.
11. A CCM according to claim 9 , wherein the ratio mg of catalyst metal/cm 2 of electrocatalytic layer ranges from 0.01 to 2.
12. A CCM according to claim 11 , wherein the ratio (weight in mg of catalyst metal)/(cm 2 of electrocatalytic layer), when hydrogen is used as fuel, ranges from 0.01 to 0.7 mg/cm 2 , when methanol is used it ranges from 0.3 to 1 mg/cm 2 at the anode side and from 0.5 to 2 mg/cm 2 at the cathode side.