To provide a membrane electrode assembly capable of forming a fuel cell excellent in power generation efficiency, and a polymer electrolyte fuel cell. The membrane electrode assembly of the present invention comprises an anode having a catalyst layer containing a proton-conducting polymer and a catalyst, a cathode having a catalyst layer containing a proton-conducting polymer and a catalyst, and a solid polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton-conducting polymer contained in the catalyst layer of at least one of the anode and the cathode, is a polymer (H) having a cyclic ether structural unit and an ion exchange group, and the solid polymer electrolyte membrane contains a fluorinated polymer (S) having an ion exchange group; and the thickness of the solid polymer electrolyte membrane is from 5 to 15 μm, and the ratio of the content M1 [mol %] of the cyclic ether structure unit to the thickness T1 [μm] of the solid polymer electrolyte membrane is 4.5 or more.

To provide a membrane electrode assembly capable of forming a fuel cell excellent in power generation efficiency, and a polymer electrolyte fuel cell. The membrane electrode assembly of the present invention comprises an anode having a catalyst layer containing a proton-conducting polymer and a catalyst, a cathode having a catalyst layer containing a proton-conducting polymer and a catalyst, and a solid polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton-conducting polymer contained in the catalyst layer of at least one of the anode and the cathode, is a polymer (H) having a cyclic ether structural unit and an ion exchange group, and the solid polymer electrolyte membrane contains a fluorinated polymer (S) having an ion exchange group; and the thickness of the solid polymer electrolyte membrane is from 5 to 15 μm, and the ratio of the content M1 [mol %] of the cyclic ether structure unit to the thickness T1 [μm] of the solid polymer electrolyte membrane is 4.5 or more.

Provided are composite electrolytes having a bio-based gel electrolyte in an ordered structure of a porous solid. In some embodiments, the gel electrolyte includes a glycolate gel, a glycerate gel, a bio-based compound-derived gel or a combination thereof. Also provided are electrochemical systems (electrodeposition), redox flow batteries, fuel cells, lithium-ion batteries and lithium-metal batteries including the composite electrolytes, and methods for producing gel electrolytes. In some embodiments, the methods including reacting a polyol, optionally ethylene glycol, propanediol, butanediol, pentanediol, diethylene glycol, glycerol, or any combination thereof, with a lithium metal and/or a lithium salt, optionally lithium hydroxide, a sodium salt, optionally sodium hydroxide (NaOH), NaTFSI, NaBF.sub.4, or NaPF.sub.6; an aluminum salt; a potassium salt, a magnesium salt; a calcium salt; a zinc salt; or any combination thereof.

A membrane electrode assembly includes an electrolyte membrane, and a pair of electrode layers which sandwich the electrolyte membrane. The pair of electrode layers include a pair of catalyst layers which sandwich the electrolyte membrane, and a pair of gas diffusion layers disposed on the pair of catalyst layers on opposite sides to the electrolyte membrane. At least one catalyst layer contains a fibrous electric conductor, catalyst particles, a particulate electric conductor, and a proton-conductive resin. The at least one catalyst layer has a first region at a distance of 200 nm or less from the fibrous electric conductor, and a second region at a distance of more than 200 nm from the fibrous electric conductor. Pores are present in the first and second regions. A mode diameter M1 of the pores in the first region and a mode diameter M2 of the pores in the second region satisfy M1<M2.

A method for operating a fuel cell assembly, the fuel cell assembly including a fuel cell stack having a solid oxide fuel cell, the solid oxide fuel cell having an anode, a cathode, and an electrolyte, the method including: determining a temperature setpoint for the fuel cell stack, for output products of the fuel cell stack, or both; and controlling a volume of oxidant provided to the anode in response to the determined temperature setpoint to control a temperature of the fuel cell stack, a temperature of the output products of the fuel cell stack, or both.

Methods and systems are provided for transporting and hydrating a redox flow battery system with a portable field hydration system. In one example, the redox flow battery system may be hydrated with the portable field hydration system in a dry state, in the absence of liquids. In this way, a redox flow battery system may be assembled and transported from a battery manufacturing facility to an end-use location off-site while the redox flow battery system is in the dry state, thereby reducing shipping costs, design complexities, as well as logistical and environmental concerns.

Methods and systems are provided for transporting and hydrating a redox flow battery system with a portable field hydration system. In one example, the redox flow battery system may be hydrated with the portable field hydration system in a dry state, in the absence of liquids. In this way, a redox flow battery system may be assembled and transported from a battery manufacturing facility to an end-use location off-site while the redox flow battery system is in the dry state, thereby reducing shipping costs, design complexities, as well as logistical and environmental concerns.

Provided are an electrochemical catalyst and a preparation method therefor. The preparation method for an electrochemical catalyst may comprise the steps of preparing a base metal aqueous solution containing a base metal, hydrothermally synthesizing a base structure containing an oxide of the base metal by using the base metal aqueous solution, and using a heat treatment method for the base structure in a sulfur (S)-containing reactive gas atmosphere, exchanging oxygen (O) on the surface of the base structure with sulfur (S) of the reactive gas to form a catalyst structure which has a core structure containing the oxide of the base metal and a shell structure containing a sulfide of the base metal.

The present invention provides a method of operating a fuel cell, which method enables a polymer electrolyte membrane to be humidified sufficiently under high-temperature conditions, and can obtain excellent power generation performance. The present invention is a method of operating a fuel cell including a membrane electrode assembly containing an electrolyte membrane, catalyst layers, and gas diffusion layers, the method including a step of setting the operating temperature of the fuel cell at 100° C. or more, wherein, in the step, the relative humidity of supply gas to be supplied to the fuel cell is 70% or more, and the back pressure of the supply gas is 330 kPa or more.

An object of the present invention is to provide a hydrogen permeable material having excellent hydrogen permeability. Another object of the present invention is to provide a composite member and a fuel cell including the hydrogen permeable material. The hydrogen permeable material comprises a perovskite type compound represented by the following general formula (1a). In another embodiment, the hydrogen permeable material comprises a hydrogen-containing perovskite type compound, which is the perovskite type compound represented by the general formula (1a) with introduced hydride ion (H.sup.−). Wherein M is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca, x is a numerical value of 0 or more and 0.3 or less, y is a numerical value of more than 0 and 0.75 or less, w is a value at which an average valence of In is +1.0 or more and +2.5 or less, and y≥w.

M.sub.1-xZr.sub.1-yIn.sub.yO.sub.3-x-0.5y-2  (1a)