A radiation-assisted (typically solar-assisted)electrolyzer cell and panel for high-efficiency hydrogen production comprises a photoelectrode and electrode pair, with said photoelectrode comprising either a photoanode electrically coupled to a cathode shared with an anode, or a photocathode electrically coupled to an anode shared with a cathode; electrolyte; gas separators; all within a container divided into two chambers by said shared cathode or shared anode, and at least a portion of which is transparent to the electromagnetic radiation required by said photoanode (or photocathode) to apply photovoltage to a shared cathode (or anode) that increases the electrolysis current and hydrogen production.

A radiation-assisted (typically solar-assisted)electrolyzer cell and panel for high-efficiency hydrogen production comprises a photoelectrode and electrode pair, with said photoelectrode comprising either a photoanode electrically coupled to a cathode shared with an anode, or a photocathode electrically coupled to an anode shared with a cathode; electrolyte; gas separators; all within a container divided into two chambers by said shared cathode or shared anode, and at least a portion of which is transparent to the electromagnetic radiation required by said photoanode (or photocathode) to apply photovoltage to a shared cathode (or anode) that increases the electrolysis current and hydrogen production.

Provided is a method for producing a nitride semiconductor photoelectrode capable of improving the light energy conversion efficiency. The method for producing a nitride semiconductor photoelectrode includes a first step of forming an n-type gallium nitride layer on an insulating or conductive substrate, a second step of forming an indium gallium nitride layer on the n-type gallium nitride layer, a third step of forming a nickel layer n the indium gallium nitride layer, and a fourth step of heat-treating the nickel layer in an oxygen atmosphere.

Provided is a method for producing a nitride semiconductor photoelectrode capable of improving the light energy conversion efficiency. The method for producing a nitride semiconductor photoelectrode includes a first step of forming an n-type gallium nitride layer on an insulating or conductive substrate, a second step of forming an indium gallium nitride layer on the n-type gallium nitride layer, a third step of forming a nickel layer n the indium gallium nitride layer, and a fourth step of heat-treating the nickel layer in an oxygen atmosphere.

A gas phase reduction device for carbon dioxide is a gas phase reduction device for carbon dioxide that exerts a catalytic function by light irradiation to generate oxidation-reduction reaction. The gas phase reduction device includes an oxidation tank in which an aqueous solution is put, a reduction tank to which carbon dioxide is supplied, a semiconductor photoelectrode installed in the aqueous solution, and a porous electrode-supported electrolyte membrane that is a joint body of an electrolyte membrane and a porous reduction electrode, the porous electrode-supported electrolyte membrane being installed between the oxidation tank and the reduction tank with the electrolyte membrane facing the oxidation tank and the porous reduction electrode facing the reduction tank. Voltage between a reference electrode installed in the aqueous solution and a reference electrode installed in contact with the electrolyte membrane is measured by a voltmeter, and a control unit increases voltage between the semiconductor photoelectrode and the porous reduction electrode in accordance with change in voltage between the reference electrodes from an initial value at start of reaction. The control unit includes a solar cell and a constant voltage power supply, and the solar cell is arranged on an extension line of a straight line from a light source toward the semiconductor photoelectrode, and generates power utilizing light emitted to and transmitted through the semiconductor photoelectrode.

A gas phase reduction device for carbon dioxide is a gas phase reduction device for carbon dioxide that exerts a catalytic function by light irradiation to generate oxidation-reduction reaction. The gas phase reduction device includes an oxidation tank in which an aqueous solution is put, a reduction tank to which carbon dioxide is supplied, a semiconductor photoelectrode installed in the aqueous solution, and a porous electrode-supported electrolyte membrane that is a joint body of an electrolyte membrane and a porous reduction electrode, the porous electrode-supported electrolyte membrane being installed between the oxidation tank and the reduction tank with the electrolyte membrane facing the oxidation tank and the porous reduction electrode facing the reduction tank. Voltage between a reference electrode installed in the aqueous solution and a reference electrode installed in contact with the electrolyte membrane is measured by a voltmeter, and a control unit increases voltage between the semiconductor photoelectrode and the porous reduction electrode in accordance with change in voltage between the reference electrodes from an initial value at start of reaction. The control unit includes a solar cell and a constant voltage power supply, and the solar cell is arranged on an extension line of a straight line from a light source toward the semiconductor photoelectrode, and generates power utilizing light emitted to and transmitted through the semiconductor photoelectrode.

The present application relates to a method for manufacturing a photoelectrode, the method comprising steps of impregnating a first transition metal oxide capable of performing photoreaction in an electrolyte, applying a voltage onto the electrolyte to generate an electrochemical oxidation reaction on the surface of the first transition metal oxide, and forming a second transition metal oxide thin film on the surface of the first transition metal oxide by irradiating light onto the first transition metal oxide at the same time as the step of applying the voltage.

The present application relates to a method for manufacturing a photoelectrode, the method comprising steps of impregnating a first transition metal oxide capable of performing photoreaction in an electrolyte, applying a voltage onto the electrolyte to generate an electrochemical oxidation reaction on the surface of the first transition metal oxide, and forming a second transition metal oxide thin film on the surface of the first transition metal oxide by irradiating light onto the first transition metal oxide at the same time as the step of applying the voltage.

Provided are methods for recovering calcium carbonate (CaCO.sub.3) and magnesium hydroxide (Mg(OH).sub.2) from an aqueous solution containing Ca.sup.2+ and Mg.sup.2+ ions. The method includes: introducing the aqueous solution into an electrochemical cell having a chamber with a photoactive cathode and an anode therein; and then performing process (a) and process (b). Process (a) entails introducing a source of (bi) carbonate anion into the cell, providing a voltage across the cell, resulting in a process (a) water reduction reaction at the cathode, and precipitating solid CaCO.sub.3 from the solution, facilitated by hydroxide ions generated from the process (a) water reduction reaction. Process (b) entails providing a voltage across the cell, resulting in a process (b) water reduction reaction at the cathode, and precipitating solid Mg(OH).sub.2 from the solution, facilitated by hydroxide ions generated from the process (b) water reduction reaction.

Provided are methods for recovering calcium carbonate (CaCO.sub.3) and magnesium hydroxide (Mg(OH).sub.2) from an aqueous solution containing Ca.sup.2+ and Mg.sup.2+ ions. The method includes: introducing the aqueous solution into an electrochemical cell having a chamber with a photoactive cathode and an anode therein; and then performing process (a) and process (b). Process (a) entails introducing a source of (bi) carbonate anion into the cell, providing a voltage across the cell, resulting in a process (a) water reduction reaction at the cathode, and precipitating solid CaCO.sub.3 from the solution, facilitated by hydroxide ions generated from the process (a) water reduction reaction. Process (b) entails providing a voltage across the cell, resulting in a process (b) water reduction reaction at the cathode, and precipitating solid Mg(OH).sub.2 from the solution, facilitated by hydroxide ions generated from the process (b) water reduction reaction.