An electrochemical cell has a first reaction chamber having a first electrode, a second reaction chamber having a second electrode, a membrane-electrode assembly having an ion-exchange membrane, and a photovoltaic system for absorbing solar energy and producing an output voltage between a first output terminal selectively couplable to the first electrode and a second output terminal selectively couplable to the second electrode. The ratio between a photosensitive area of the photovoltaic system and an active area of the first and second electrodes is less than or equal to fifty. A plurality of photovoltaic cells is selectively couplable between the first and second output terminals. An electronic control unit couples the photovoltaic cells as a function of at least one among one or more user-settable parameters, one or more signals received from an external control unit, one or more signals received from one or more sensors included in the electrochemical cell.

A carbon dioxide reduction device includes: an oxidation electrode that receives light from the outside; an oxidation bath that holds an electrolytic solution in which the oxidation electrode is immersed; an electrolyte membrane that constitutes a part of one surface of the oxidation bath excluding a surface on which the light is incident; a reduction electrode that is connected to the electrolyte membrane; a reduction unit in which the reduction electrode is disposed and to which a gas containing carbon dioxide is supplied from the outside; and a blower that generates an airflow toward the reduction electrode inside the reduction unit. The reduction electrode has a plate shape, and one surface of the reduction electrode is in contact with the electrolyte membrane.

Electrochemical cells and photoelectrochemical cells for the reduction of furfurals are provided. Also provided are methods of using the cells to carry out the reduction reactions. Using the cells and methods, furfurals can be converted into furan alcohols or linear ketones.

Electrochemical cells and photoelectrochemical cells for the reduction of furfurals are provided. Also provided are methods of using the cells to carry out the reduction reactions. Using the cells and methods, furfurals can be converted into furan alcohols or linear ketones.

This disclosure provides systems, methods, and apparatus related to photochemical diodes. In one aspect, a device include a photoanode, a photocathode, and a bipolar membrane between the photoanode and the photocathode. The photoanode comprises a first semiconductor, the first semiconductor being N-type doped, a first catalyst disposed over the first semiconductor, and the photoanode being disposed in an anolyte. The photocathode comprises a second semiconductor, the second semiconductor being P-type doped, a second catalyst disposed over the second semiconductor, and the photocathode being disposed in a catholyte. The photoanode and the photocathode are in electrical contact. A hydrogen reduction reaction or a carbon dioxide reduction reaction occurs at the photocathode and a chemical oxidation reaction occurs at the photoanode when the photocathode and the photoanode are illuminated with light.

This disclosure provides systems, methods, and apparatus related to photochemical diodes. In one aspect, a device include a photoanode, a photocathode, and a bipolar membrane between the photoanode and the photocathode. The photoanode comprises a first semiconductor, the first semiconductor being N-type doped, a first catalyst disposed over the first semiconductor, and the photoanode being disposed in an anolyte. The photocathode comprises a second semiconductor, the second semiconductor being P-type doped, a second catalyst disposed over the second semiconductor, and the photocathode being disposed in a catholyte. The photoanode and the photocathode are in electrical contact. A hydrogen reduction reaction or a carbon dioxide reduction reaction occurs at the photocathode and a chemical oxidation reaction occurs at the photoanode when the photocathode and the photoanode are illuminated with light.

Electrochemical and photoelectrochemical cells for the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and/or 2,5-diformylfuran are provided. Also provided are methods of using the cells to carry out the electrochemical and photoelectrochemical oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and/or 2,5-diformylfuran.

Electrochemical and photoelectrochemical cells for the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and/or 2,5-diformylfuran are provided. Also provided are methods of using the cells to carry out the electrochemical and photoelectrochemical oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and/or 2,5-diformylfuran.

A CO.sub.2 reduction electrode includes an active layer on an electrode base. The active layer includes a polymer that includes one or more reaction components selected from a group consisting of a CO.sub.2 reduction catalyst and an activator that bonds CO.sub.2 so as to form a CO.sub.2 reduction intermediate.

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.