The present disclosure provides phosphonated polymers that can be used, for example, as polymer electrolyte membranes (PEMs) and/or catalyst ionomeric binders for electrodes in PEM fuel cells, and more particularly for high-temperature PEM fuel cells. High-temperature PEM fuel cells that use phosphonated polymers of the present disclosure suffer from reduced or no acid leaching because, in at least some examples, phosphonic acid moieties are covalently bound to the backbone of the polymers. A phosphonated polymer include a backbone having one or more aromatic monomers, with each aromatic monomer having one or more phosphonic acid groups. A phosphonic acid group may include phosphonic acid or a functional group that is hydrolysable into phosphonic acid.

The present disclosure provides phosphonated polymers that can be used, for example, as polymer electrolyte membranes (PEMs) and/or catalyst ionomeric binders for electrodes in PEM fuel cells, and more particularly for high-temperature PEM fuel cells. High-temperature PEM fuel cells that use phosphonated polymers of the present disclosure suffer from reduced or no acid leaching because, in at least some examples, phosphonic acid moieties are covalently bound to the backbone of the polymers. A phosphonated polymer include a backbone having one or more aromatic monomers, with each aromatic monomer having one or more phosphonic acid groups. A phosphonic acid group may include phosphonic acid or a functional group that is hydrolysable into phosphonic acid.

An object is to provide an electrode catalyst layer, a membrane electrode assembly, and a polymer electrolyte fuel cell that can suppress decrease in durability of the membrane electrode assembly and decrease in power generation performance of the polymer electrolyte fuel cell by suppressing crack generation in the electrode catalyst layer. An electrode catalyst layer according to one aspect of the present invention is an electrode catalyst layer including at least: a catalytic substance; aggregates of polymer electrolytes; and polymer electrolyte fibers. In the electrode catalyst layer, an amount of phosphorus and an amount of platinum defined via elemental analysis by energy dispersive X-ray spectroscopy (EDX) satisfy a following equation (1). 0 < P/Pt≤ 3.0 ... Equation (1)

An object is to provide an electrode catalyst layer, a membrane electrode assembly, and a polymer electrolyte fuel cell that can suppress decrease in durability of the membrane electrode assembly and decrease in power generation performance of the polymer electrolyte fuel cell by suppressing crack generation in the electrode catalyst layer. An electrode catalyst layer according to one aspect of the present invention is an electrode catalyst layer including at least: a catalytic substance; aggregates of polymer electrolytes; and polymer electrolyte fibers. In the electrode catalyst layer, an amount of phosphorus and an amount of platinum defined via elemental analysis by energy dispersive X-ray spectroscopy (EDX) satisfy a following equation (1). 0 < P/Pt≤ 3.0 ... Equation (1)

The present invention provides a microtextured proton exchange membrane for a fuel cell and a processing method thereof. A plurality of concave-convex composite textures are distributed in a gradient pattern of being dense inside and sparse outside on a cathode surface of the proton exchange membrane for the fuel cell. The plurality of concave-convex composite textures are petal-shaped and each include a pit and a protrusion. The protrusion is arranged along an edge of the pit, and a plurality of hemi-ellipsoidal micro-pits are uniformly distributed on an inner surface of the pit. The cathode surface is divided into a central region, an intermediate region, and a peripheral region according to distances between the adjacent concave-convex composite textures, and in each of the regions, the distances between the adjacent concave-convex composite textures are gradually increased from inside to outside in a gradient pattern.

The present invention provides a microtextured proton exchange membrane for a fuel cell and a processing method thereof. A plurality of concave-convex composite textures are distributed in a gradient pattern of being dense inside and sparse outside on a cathode surface of the proton exchange membrane for the fuel cell. The plurality of concave-convex composite textures are petal-shaped and each include a pit and a protrusion. The protrusion is arranged along an edge of the pit, and a plurality of hemi-ellipsoidal micro-pits are uniformly distributed on an inner surface of the pit. The cathode surface is divided into a central region, an intermediate region, and a peripheral region according to distances between the adjacent concave-convex composite textures, and in each of the regions, the distances between the adjacent concave-convex composite textures are gradually increased from inside to outside in a gradient pattern.

To provide an electrolyte membrane wherein pinholes are less likely to occur even when used in a cell having an anode and a cathode under voltage for a prolonged period of time, as well as an electrolysis apparatus and a redox flow battery which contain the membrane. An electrolyte membrane comprising a fluorinated polymer containing ion-exchange groups and a woven fabric, wherein said woven fabric consists of yarns A extending in one direction and yarns B extending in a direction orthogonal to said yarns A, the aspect ratio YA.sub.CA2/YA.sub.CA1 exceeds 1 and is larger than the aspect ratio YA.sub.A2/YA.sub.A1, and the aspect ratio YA.sub.CB2/YA.sub.CB1 exceeds 1 and is larger than the aspect ratio YA.sub.B2/YA.sub.B1. (YA.sub.CA2, YA.sub.CA1, YA.sub.A2, YA.sub.A1, YA.sub.CB2, YA.sub.CB1, YA.sub.B2 and YA.sub.B1 are as defined in the specification.)

To provide an electrolyte membrane wherein pinholes are less likely to occur even when used in a cell having an anode and a cathode under voltage for a prolonged period of time, as well as an electrolysis apparatus and a redox flow battery which contain the membrane. An electrolyte membrane comprising a fluorinated polymer containing ion-exchange groups and a woven fabric, wherein said woven fabric consists of yarns A extending in one direction and yarns B extending in a direction orthogonal to said yarns A, the aspect ratio YA.sub.CA2/YA.sub.CA1 exceeds 1 and is larger than the aspect ratio YA.sub.A2/YA.sub.A1, and the aspect ratio YA.sub.CB2/YA.sub.CB1 exceeds 1 and is larger than the aspect ratio YA.sub.B2/YA.sub.B1. (YA.sub.CA2, YA.sub.CA1, YA.sub.A2, YA.sub.A1, YA.sub.CB2, YA.sub.CB1, YA.sub.B2 and YA.sub.B1 are as defined in the specification.)

The invention relates to a fuel cell (1) for a fuel cell stack (11), comprising a polymer membrane (2) which serves as an electrolyte and has respectively on both sides a catalyst layer (3, 4) for forming an anode (3) on the one side and a cathode (4) on the other side, a gas diffusion layer (5) and a bipolar plate (6) being applied to each of the two analyst layers (3, 4). According to the invention, a short-circuit element (7) is applied, preferably printed, to at least one bipolar plate (6), namely on the side facing away from the gas diffusion layer (5). The invention also relates to a fuel cell stack (11) and to a method for operating a fuel cell stack (11).

The invention relates to a fuel cell (1) for a fuel cell stack (11), comprising a polymer membrane (2) which serves as an electrolyte and has respectively on both sides a catalyst layer (3, 4) for forming an anode (3) on the one side and a cathode (4) on the other side, a gas diffusion layer (5) and a bipolar plate (6) being applied to each of the two analyst layers (3, 4). According to the invention, a short-circuit element (7) is applied, preferably printed, to at least one bipolar plate (6), namely on the side facing away from the gas diffusion layer (5). The invention also relates to a fuel cell stack (11) and to a method for operating a fuel cell stack (11).