A positive electrode for an air battery includes a current collector and a porous layer including an electroconductive material. The current collector includes a base having a first major surface, and a plurality of projections disposed on at least the first major surface of the base. The first major surface of the base is a planar surface. The porous layer is disposed on the first major surface of the base and is in direct contact with the first major surface. The projections are in direct contact with the porous layer in the interior of the porous layer.

A catalyst layer comprising an electrocatalyst and an oxygen evolution catalyst, wherein the oxygen evolution catalyst comprises a crystalline metal oxide comprising: (i) one of more first metals selected from the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, magnesium, calcium, strontium, barium, sodium, potassium, indium, thallium, tin, lead, antimony and bismuth; (ii) one or more second metals selected from the group consisting of Ru, Ir, Os and Rh; and (iii) oxygen
characterised in that: (a) the atomic ratio of first metal(s):second metal(s) is from 1:1.5 to 1.5:1 (b) the atomic ratio of (first metal(s)+second metal(s)):oxygen is from 1:1 to 1:2 is disclosed.

A catalyst layer including an electrocatalyst and an oxygen evolution catalyst, wherein the oxygen evolution catalyst includes a crystalline metal oxide including: (i) one of more first metals selected from the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, magnesium, calcium, strontium, barium, sodium, potassium, indium, thallium, tin, lead, antimony and bismuth; (ii) one or more second metals selected from the group consisting of Ru, Ir, Os and Rh; and (iii) oxygen
characterized in that: (a) the atomic ratio of first metal(s):second metal(s) is from 1:1.5 to 1.5:1 (b) the atomic ratio of (first metal(s)+second metal(s)):oxygen is from 1:1 to 1:2 is disclosed.

An electrode for use in an electrochemical cell, especially a zinc-bromine flow battery or a hydrogen/bromine flow battery, and methods for manufacturing and using the electrode is provided. The electrode has a metal substrate and a catalytic coating applied onto the substrate wherein the catalytic coating has a Ru-rich mixture of ruthenium and having 70-80 mol % Ru, 1-5 mol % Pt and 17-25 mol % Ir. The catalytic coating composition exhibits a surprisingly high voltage efficiency and operating lifetime despite its relatively low Ir/Ru and Pt/Ru ratios. The underlying metal substrate is for example a porous Ti layer or a layer with titanium suboxides Ti.sub.xO.sub.y.

An electrochemical cell includes a bifunctional air cathode, an anode, and a ceramic electrolyte separator disposed substantially between the bifunctional air cathode and the anode. The anode includes a solid metal and an electrolyte configured to transition to a liquid phase in an operating temperature range. The electrolyte includes at least one of an alkali oxide, boron oxide, a carbonate, a phosphate, and a group III-X transition metal oxide.

A metal-hydrogen battery includes a first electrode, a second electrode, and an electrolyte disposed between the first electrode and the second electrode. The second electrode includes a bi-functional catalyst to catalyze both hydrogen evolution reaction and hydrogen oxidation reaction at the second electrode.

An electrode comprises an acid treated, cathodically cycled carbon-comprising film or body. The carbon consists of single walled nanotubes (SWNTs), pyrolytic graphite, microcrystalline graphitic, any carbon that consists of more than 99% sp.sup.2 hybridized carbons, or any combination thereof. The electrode can be used in an electrochemical device functioning as an electrolyzer for evolution of hydrogen or as a fuel cell for oxidation of hydrogen. The electrochemical device can be coupled as a secondary energy generator into a system with a primary energy generator that naturally undergoes generation fluctuations. During periods of high energy output, the primary source can power the electrochemical device to store energy as hydrogen, which can be consumed to generate electricity as the secondary source during low energy output by the primary source. Solar cells, wind turbines and water turbines can act as the primary energy source.

An electrochemical cell includes a bifunctional air cathode, an anode, and a ceramic electrolyte separator disposed substantially between the bifunctional air cathode and the anode. The anode includes a solid metal and a liquid electrolyte phase. The liquid electrolyte phase includes at least one of an alkali oxide, boron oxide, a group V transition metal oxide, and a group VI transition metal oxide.

A gas diffusion layer for a metal-air battery, the gas diffusion layer including: a porous layer including non-conductive fiber structures, a conductive carbon layer including a carbon material that is disposed on a surface of a non-conductive fiber structure of the plurality of non-conductive fiber structures.

A gas diffusion layer for a metal-air battery, the gas diffusion layer including: a porous layer including non-conductive fiber structures, a conductive carbon layer including a carbon material that is disposed on a surface of a non-conductive fiber structure of the plurality of non-conductive fiber structures.