A catalyst-coated membrane (CCM) for use in a water electrolyser, having a laminate structure comprising: a first layer comprising a first membrane component having a cathode catalyst layer disposed on a first face thereof; a second layer comprising a second membrane component having an anode catalyst layer disposed on a first face thereof; and an intermediate layer disposed between the first and second layers, comprising a third membrane component having a recombination catalyst layer disposed on a first face thereof is disclosed. The CCM is useful within a water electrolyser. The recombination catalyst layer reduces the risk associated with hydrogen crossover and allows thinner membranes with lower resistance to be used.

An electrochemical cell of an electrochemical hydrogen compressor is provided with a first flow field member having a hydrogen gas flow field and a second flow field member having a water channel. The first flow field member is located between the anode electrode and the anode separator. The second flow field member is located between the anode electrode and the first flow field member. A first porous member is located between the first flow field member and the second flow field member. A second porous member is located between the second flow field member and the anode electrode.

An electrochemical cell of an electrochemical hydrogen compressor is provided with a first flow field member having a hydrogen gas flow field and a second flow field member having a water channel. The first flow field member is located between the anode electrode and the anode separator. The second flow field member is located between the anode electrode and the first flow field member. A first porous member is located between the first flow field member and the second flow field member. A second porous member is located between the second flow field member and the anode electrode.

A reinforced separator for alkaline hydrolysis includes a porous support, a first porous polymer layer contiguous with one side of the support and a second porous polymer layer contiguous with the other side of the support, characterized in that the maximum pore diameter at the outer surface of the first porous polymer layer PD.sub.max(1) and of the second porous polymer layer PD.sub.max(2) are different from each other and wherein a ratio between PD.sub.max(2) and PD.sub.max(1) is between 1.25 and 10.

A reinforced separator for alkaline hydrolysis includes a porous support, a first porous polymer layer contiguous with one side of the support and a second porous polymer layer contiguous with the other side of the support, characterized in that the maximum pore diameter at the outer surface of the first porous polymer layer PD.sub.max(1) and of the second porous polymer layer PD.sub.max(2) are different from each other and wherein a ratio between PD.sub.max(2) and PD.sub.max(1) is between 1.25 and 10.

The present invention provides a water electrolysis method comprising: supplying at least water into an electrolysis cell which includes a solid polymer electrolyte membrane, and an anode and a cathode disposed sandwiching the solid polymer electrolyte membrane therebetween; and providing a potential P between the anode and the cathode to generate oxygen from the anode, wherein an oxidation catalyst containing at least one of first transition metals is present on at least a part of a surface of the anode, and the potential P satisfies P1<P<P2, wherein P1 indicates a lowest potential at which oxygen is generated from the anode, and P2 indicates a lowest potential P2 at which a quantitative index of a dissolved chemical species derived from the oxidation catalyst begins to show potential dependence.

The present invention provides a water electrolysis method comprising: supplying at least water into an electrolysis cell which includes a solid polymer electrolyte membrane, and an anode and a cathode disposed sandwiching the solid polymer electrolyte membrane therebetween; and providing a potential P between the anode and the cathode to generate oxygen from the anode, wherein an oxidation catalyst containing at least one of first transition metals is present on at least a part of a surface of the anode, and the potential P satisfies P1<P<P2, wherein P1 indicates a lowest potential at which oxygen is generated from the anode, and P2 indicates a lowest potential P2 at which a quantitative index of a dissolved chemical species derived from the oxidation catalyst begins to show potential dependence.

An ion conducting polymer comprising a modified poly(phenylene oxide) is described. In an exemplary modified polymer, a portion of the monomeric units are attached to a sulfonate-substituted arylamino moiety, such as a monovalent derivative of phenoxy aniline trisulfonate (BOATS), to form a monomeric unit with a charged side chain. Ion conducting polymers can also be prepared with polyether-containing side chains. The ion conducting polymer can be used to prepare ion exchange membranes which can be used in a variety of applications, such as in non-aqueous redox flow batteries and related energy storage systems.

An ion conducting polymer comprising a modified poly(phenylene oxide) is described. In an exemplary modified polymer, a portion of the monomeric units are attached to a sulfonate-substituted arylamino moiety, such as a monovalent derivative of phenoxy aniline trisulfonate (BOATS), to form a monomeric unit with a charged side chain. Ion conducting polymers can also be prepared with polyether-containing side chains. The ion conducting polymer can be used to prepare ion exchange membranes which can be used in a variety of applications, such as in non-aqueous redox flow batteries and related energy storage systems.

Anion exchange polymers having high OH.sup.− conductivity, chemical stability, and mechanical stability have been developed for use in AEMs. The anion exchange polymers have stable hydrophobic polymer backbones, stable hydrophilic quaternary ammonium cationic groups, and hydrophilic phenolic hydroxyl groups on the polymer side chains. The polymers have polymer backbones free of ether bonds, hydrophilic polymer side chains, and piperidinium ion-conducting functionality, which enables efficient and stable operation in water or CO.sub.2 electrolysis, redox flow battery, and fuel cell applications. The polymer comprises a plurality of repeating units of formula (I)

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Anion exchange membranes and membrane electrode assemblies incorporating the anion exchange polymers are also described.