The invention is directed to a process to convert carbon dioxide to methane by contacting an aqueous solution comprising dissolved carbon dioxide with an electron charged packed bed comprising of a carrier, suitably activated carbon granules, and a biofilm of microorganisms under anaerobic conditions, wherein more than 90 mol % of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion.

In a case where an alkali aqueous solution is used as an electrolyte, provided are an oxygen catalyst excellent in catalytic activity and composition stability, an electrode having high activity and stability using this oxygen catalyst, and an electrochemical measurement method that can evaluate the catalytic activity of the oxygen catalyst alone. The oxygen catalyst is an oxide having peaks at positions of 2θ=30.07°±1.00°, 34.88°±1.00°, 50.20°±1.00°, and 59.65°±1.00° in an X-ray diffraction measurement using a CuKα ray, and having constituent elements of bismuth, ruthenium, sodium, and oxygen. An atom ratio O/Bi of oxygen to bismuth and an atom ratio O/Ru of oxygen to ruthenium are both more than 3.5.

In a case where an alkali aqueous solution is used as an electrolyte, provided are an oxygen catalyst excellent in catalytic activity and composition stability, an electrode having high activity and stability using this oxygen catalyst, and an electrochemical measurement method that can evaluate the catalytic activity of the oxygen catalyst alone. The oxygen catalyst is an oxide having peaks at positions of 2θ=30.07°±1.00°, 34.88°±1.00°, 50.20°±1.00°, and 59.65°±1.00° in an X-ray diffraction measurement using a CuKα ray, and having constituent elements of bismuth, ruthenium, sodium, and oxygen. An atom ratio O/Bi of oxygen to bismuth and an atom ratio O/Ru of oxygen to ruthenium are both more than 3.5.

The present invention provides an oxygen generation electrode provided with a catalyst layer having a high specific electric conductivity, and having excellent durability such that even when an acidic electrolyte is electrolyzed, the catalyst components are unlikely to be consumed and long-term electrolysis can be performed. The oxygen generation electrode is an oxygen generation electrode 10 provided with a substrate 2 formed with titanium or a titanium alloy, and a catalyst layer 4 disposed on the substrate 2 and formed with a mixed metal oxide, wherein the catalyst layer 4 satisfies at least any one of the following condition (1) and condition (2). Condition (1): containing ruthenium, tin, and trivalent or higher polyvalent metal element excluding a tetravalent metal element. Condition (2): containing ruthenium and tin, and having a content of ruthenium of 40 mol % or more based on the total content of the ruthenium and tin.

The present invention provides an oxygen generation electrode provided with a catalyst layer having a high specific electric conductivity, and having excellent durability such that even when an acidic electrolyte is electrolyzed, the catalyst components are unlikely to be consumed and long-term electrolysis can be performed. The oxygen generation electrode is an oxygen generation electrode 10 provided with a substrate 2 formed with titanium or a titanium alloy, and a catalyst layer 4 disposed on the substrate 2 and formed with a mixed metal oxide, wherein the catalyst layer 4 satisfies at least any one of the following condition (1) and condition (2). Condition (1): containing ruthenium, tin, and trivalent or higher polyvalent metal element excluding a tetravalent metal element. Condition (2): containing ruthenium and tin, and having a content of ruthenium of 40 mol % or more based on the total content of the ruthenium and tin.

The present disclosure relates to a carbon dioxide capture device comprising a first reactor and a second reactor both of which show a (photo)anode containing or connected to oxygen evolution and/or carbon dioxide evolution catalyst(s) and a (photo)cathode containing or connected to an oxygen reduction catalyst, wherein the first reactor comprises an anion exchange membrane placed between the porous (photo)anode and porous (photo)cathode, and the second reactor comprises a proton exchange membrane placed between the porous (photo)anode and porous (photo)cathode. On the porous (photo)cathode side of the first reactor there is a fluid inlet able to carry carbon dioxide, air and water, and on the side of the porous (photo)cathode of the second reactor there is a fluid outlet able to carry carbon dioxide and water.

Disclosed is a hypochlorous acid generating electrode that is substantially free from rhodium, which is comparable in performance to a rhodium-containing electrode and is more durable than the rhodium-containing electrode. The electrode to be used for generating hypochlorous acid by electrolyzing water that contains a chloride ion has excellent hypochlorous acid water generation ability and durability, in which the electrode has an electrode substrate comprising titanium or titanium alloy, and a composite layer that is electrically connected with the electrode substrate and that contains iridium or a compound thereof, tantalum or a compound thereof, and ruthenium or a compound thereof and/or platinum, and does not contain rhodium oxide.

Disclosed is a hypochlorous acid generating electrode that is substantially free from rhodium, which is comparable in performance to a rhodium-containing electrode and is more durable than the rhodium-containing electrode. The electrode to be used for generating hypochlorous acid by electrolyzing water that contains a chloride ion has excellent hypochlorous acid water generation ability and durability, in which the electrode has an electrode substrate comprising titanium or titanium alloy, and a composite layer that is electrically connected with the electrode substrate and that contains iridium or a compound thereof, tantalum or a compound thereof, and ruthenium or a compound thereof and/or platinum, and does not contain rhodium oxide.

The present invention relates to a photo-electrochemical device for production of a gas, liquid or solid using concentrated electromagnetic irradiation. The device comprises a photovoltaic component configured to generate charge carriers from the concentrated electromagnetic irradiation; and an electrochemical component configured to carry out electrolysis of a reactant. The photovoltaic component contacts the electrochemical component at a solid interface to form an integrated photo-electrochemical device; and further includes at least one reactant channel or a plurality of reactant channels extending between the photovoltaic component and the electrochemical component to transfer heat and the reactant from the photovoltaic component to the electrochemical component. The integrated photo-electrochemical device and auxiliary devices (such as concentrator, flow controllers) build a system which can flexibly react to changes in operating condition and guarantee best performance.

The present invention provides a tin oxide forming composition and a tin oxide forming method using the tin oxide forming composition. The tin oxide forming composition of the present invention is easy to manufacture and is capable of forming a tin oxide with a high yield.